california dept. of health services study

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Acute Health Effects of the

Cantara Metam Sodium Spill

An Epidemiologic Assessment

C A L I F O R N I A D E P A R T M E N T O F H E A L T H S E R V I C E S

Environmental Epidemiology & Toxicology Program

JUNE 1992


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E X E C U T I V E S U M M A R Y

On July 14, 1991, a major pesticide spill occurred in a remote area of Northern California near the

town of Dunsmuir. Due to a train derailment, 19,000 gallons of the herbicide metam sodium were

released into the Sacramento River. Nearly all aquatic life in a 45-mile segment of the river from the spill

site to Lake Shasta was killed as the chemical flowed downstream. Individuals near the river reported a

variety of symptoms from exposure to vapors released by the decomposing chemical. This report,

prepared by the California Department of Health Services (DHS) Environmental Epidemiology and

Toxicology Program (EETP), examines health effects of the spill reported to the local medical community

from July 14 to August 16,1991.

F I N D I N G S

Sourccs of information for this investigation included area hospital records, pesticide illness

reports filed by private physicians, and questionnaires completed by individuals using the temporary

evacuation and triage center in Dunsmuir. Cases were defined as anyone who sought evaluation at one

of these three sources of information for symptoms they felt were spill-related.

During the one-month period of study, 705 cases were identified. These individuals accounted

for a total of 848 medical visits. The number of medical evaluations was approximately equally

distributed between the hospital emergency rooms, private physicians, and triage center. Most of the

cases were from Dunsmuir (70.6%), Mt. Shasta (7.2%) and Castel la (6.4%) which were the three

communities closest to the spill site. By age distribution, the largest number of cases were in the 30-39

age group. Relatively few cases were recorded for ages 50 and over. For each age group, more females

than males reported symptoms.

A wide range of symptoms were recorded. Overall, the most common symptoms were headache

(63.8%), eye irritation (48.5%), nausea (46.2%), throat irritation (42.0%), dizziness (29.6%), shortness of

breath (27.1%), diarrhea (25.3%), nasal irritation (23.1%), and chest tightness (22.4%). The types of

symptoms reported varied little by gender and age. However, there were significantly fewer symptoms

per person on average for those less than 20 and those greater than 69 years of age. Odors were reported

by 35% of the cases. The most common odor reported was a sulfur/rotten egg smell. Symptoms did not

differ significantly between those reporting an odor and those who reported no odor. Smokers appeared

to have more symptoms and higher frequency rates for nearly all symptoms than those identified as non-

smokers. However, data on odor detection and smoking history was missing for a large number of cases.

Many people reported symptoms more than one week after the spill. The types of symptoms

reported were similar although a significantly higher percentage of weakness, diarrhea, cough, and rash

were recorded among those reporting symptoms a week or more later. Most exposure and symptom

onsets appeared to occur within the first two days after the spill. However, nearly one-quarter of the

cases in which initial exposure and symptom onset dates were known app>eared to delay evaluation for

seven or more days after symptom onset.

Seven hospitalizations were recorded. There were four respiratory-related admissions, two cases

of possible syncope (fainting), and one case of a cardiac arrhythmia in a person involved in initial clean

up activities. All were discharged by July 28. There were no fatalities.

Eight women who were pregnant at the time of the spill were identified through the

investigation. No adverse pregnancy outcomes were identified although two women did obtain

therapeutic abortions in part because of concerns over exposure effects.

An analysis of Dunsmuir cases suggested that nearly 14% of the population within the city limits

sought medical evaluation. Within the Dunsmuir area, it appeared that exposures occurred on both sides

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of the river at distances of up to 1500 feet away from the river. In an analysis using serial 300 foot zones

away from each side of the river, symptom rates appeared highest among the population who lived

within 300 feet of the river (21.2%), decreased and remained relatively constant at 12-15% for the

population living within 301-600, 601-900, and 901-1200 feet from the river, and increased to 19.8% for

those living between 1201-1500 feet from the river.

C O N C L U S I O N S

The Cantara incident had an undeniably devastating environmental impact on the affected

portion of the Sacramcnto River. The full extent of health effects has not been determined. The data in

this report was observational, uncontrolled, and subject to many types of bias. It can not support absolute

cause and effect relationships. However, several important points can be made.

Approximately 700 individuals sought medical attention for symptoms they believed were

related to the spill-a highly significant finding given the sparse population of the area. The finding that

14% of Dunsmuir city residents sought mcdical care is quite striking. However, the study did not include

those who did not seek care. It is likely the number of cases included in this investigation is an

underestimate of the true number of people affected. Symptoms were consistent with exposure to irritant

gases. Irritation of the eyes, gastrointestinal tract, respiratory tract and skin occurred. Non-specific

neurologic complaints also were common. Gender, age, and smoking status were factors which appeared

to affect symptom reporting.

Exposure assessment is limited by a lack of environmental data for the first two days after the

spill. The exact types and concentrations of substances which were present is not known. Because metam

sodium decomp>oscs rapidly upon dilution in water, exposure-related symptoms are believed to be

secondary to its volatile breakdown products of which the most likely is methyl isothiocyanate (MITC).

Some symptoms probably occurrcd at chemical concentrations below odor thresholds which is consistent

with MITC toxicology. Based on odor reports, exposure to hydrogen sulfide also occurred although its

significance in producing symptoms is unknown. Because there were no fatalities and few

hospitalizations, it is unlikely that prolonged, high-level exposures occurred.

Although most exposure and symptom onsets appeared to occur within the first two days after

the spill, symptoms unexpectedly were being reported many days after the spill. Later symptom reports

may be due to: delays in seeking medical evaluation; attributing non-spill-related symptoms to the

incident; psychologically mediated symptoms similar to that seen with post-traumatic stress disorder;

slowly resolving or chronic health problems related to exposure; or unrecognized or underestimated

toxicologic properties of the spilled chemical such as persistence in the environment and sensitization of

certain individuals to the chcmicals. The long-term health effects of exposure, including effects on the

reproductive system remain to be determined.

R E C O M M E N D A T I O N S

The incident has raised questions regarding the lack of a hazardous material classification for

transportation of metam sodium, the overall safety and toxicology of metam sodium, the effectiveness

and efficiency of the emergency response of public health agencies, and health care access in a crisis

situation. Specific DHS follow-up activities which are currently in progress to address these concerns

i n c l u d e :

Follow-up Investigation of the Affected Population: DHS-EETP recently conducted a door-to-

door survey in the city of Dunsmuir to determine the extent of symptoms experienced and further define

exjx)sure effects. The investigation includes individuals not seen by health care providers and will also

address health care access in the area. Results wil l be released at a later date.

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Birth Defects Monitoring: DHS is monitoring prcgnancy and birth outcomes in the affected area

through the DHS Genetic Disease Branch and its Birth Defects Monitoring Program. An interim report is

exp>ected by Fall, 1992.

Characterization of Metam Sodium: Staff from DHS laboratories are characterizing metam

sodium and its breakdown products more precisely in order to improve exposure modelling. Improved

methods of measuring metam sodium and other environmental contaminants are being investigated

(metam sodium toxicology has been extensively reviewed and will be discussed in an upcoming

document produced by Cal-EPA).

Emergency Response Capability Improvement: DHS has collaborated with other agencies to

improve the emergency response for railroad chemical spills. Staff currently participate on the Railroad

Accident Prevention and Immediate Deployment Force (RAPID) which recently was established through

State Senate Bill 48. DHS also is evaluating its internal emergency response procedures and methods of

improvement. Field communications equipment is being upgraded. Simulated mock emergencies

similar to the Cantara incident are planned periodically as a training tool for DHS staff.

Communication of Risks and Results: DHS will maintain a strong presence in Dunsmuir for the

next several months to communicate with community members and physicians about health concerns.

Collaboration with Other State and Federal Agencies: DHS will continue to work with other

public health agencies to support tighter regulations which protect public health in the areas of chemical

classification, transportation, and marketing.

A C K N O W L E D G M E N T S

This document was produced by the California Department of Health Services (DHS)

Environmental Epidemiology and Toxicology Program (EETP), Lynn Goldman, Chief. David Hewitt

(DHS-EETP) and Richard Kreutzer (DHS-EETP) were the authors. The report would not have been

possible without the generous assistance of Terri Barber (Siskiyou County Environmental Health

Department) and many other county health department staff.

Co-investigators of the incident included; Dennis Shusterman, California Environmental

Protection Agency (Cal-EPA), who was first on the scene and produced the initial surveillance forms;

Richard Sun (DHS Infectious Disease Branch); Dena Mangiamele (DHS Veterinary Public Health Unit)

Lynn Goldman (DHS-EETP) and Richard Jackson (Cal-EPA). Additional support with data abstraction

and analysis was provided by Glen Ikawa (DHS Epidemiology and Disease Prevention Section (EDPS),

Jennifer Mann (Cal-EPA), Theresa Saunders (DHS-EETP), and Joanne Siebles (DHS-EDPS).

Toxicologic support and advice were provided by Michael DiBartolomeis (Cal-EPA), Asa

Bradman (DHS-EETP), Robert Howd (Cal-EPA), and Richard Lam (Cal-EPA). Geographic and population

data were provided by Robert Sellman (Planning Director, Siskiyou County). Maps were produced by

Tim Lomas (DHS-EETP) and Rachel Broadwin (DHS-EETP). Peer review and suggestions were provided

by Amy Casey (DHS-EETP), Lynn Goldman (DHS-EETP) Martin Kharrazi (DHS-EETP), Denise Koo

(DHS-EETP), Daniel Smith (DHS-EETP), and Suzanne Teran (DHS-EETP). David Simmons and Theresa

Saunders (DHS-EETP) formatted and assembled the report.

Special thanks goes to the Mt. Shasta Mercy Hospital, the Redding Medical Center and Redding

Mercy Hospital medical records staffs for their assistance in this investigation.

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Table o f Contents

L I S T O F T A B L E S A N D H G U R E S v

B A C K G R O U N D 6

D e s c r i p t i o n o f t h e I n c i d e n t 6

T o x i c o l o g y o f M e t a m S o d i u m a n d B y p r o d u c t s 8

D H S - E E T P R e s p o n s e t o t h e I n c i d e n t 1 0

M E T H O D S 1 1

D a t a C o l l e c t i o n I n s t r u m e n t s 1 1

D a t a S o u r c e s 1 2

D a t a A n a l y s i s 1 2

R E S U L T S 1 4

D a t a S o u r c e s 1 4

C l i n i c a l M a n i f e s t a t i o n s o f E x p o s u r e 1 6

H o s p i t a l i z a t i o n s 2 5

P r e g n a n c i e s 2 5

H e a l t h I m p a c t o f t h e S p i l l o n D u n s r n u i r 2 5

D I S C U S S I O N ^

L i m i t a t i o n s o f T h i s S t u d y 2 9

M a j o r F i n d i n g s 2 9

C O N C L U S I O N S 3 1

R E C O M M E N D A T I O N S 3 ] _

G e n e r a l R e c o m m e n d a t i o n s 3 1

S p e c i fi c F o l l o w - u p A c t i v i t i e s I n P r o g r e s s 3 3

R E F E R E N C E S 3 5

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List of Tables and Figures

TABLES

1 . O d o r a n d I r r i t a n t T h r e s h o l d s o f M e t a m S o d i u m B r e a k d o w n P r o d u c t s 9

2 . S i t e o f S p i l l - R e l a t e d M e d i c a l E v a l u a t i o n 1 4

3 . C i t y o f R e s i d e n c e f o r C a s e s 1 4

4 . O d o r s R e p o r t e d b y C a s e s 1 6

5 . N u m b e r ( P e r c e n t ) o f C a s e s R e p o r t i n g S e l e c t e d S y m p t o m s 1 8

6 . Num ber ( Pe r cen t ) o f Cases Repor t i ng Se lec t ed Sym pt om s by G ender 19

7. Percent of Cases Repor t ing Selected Symptoms by 10-year Age Groups 20

8. Number (Percent) of Cases Reporting Selected Symptoms by Odor Detection Status 21

9. Number (Percent) of Cases Reporting Selected Symptoms by Smoking Status 22

10. Number (Percent) of All Visits in Which Selected Symptoms arc Rep>orted by Date Evaluated 23

1 1 . I n i t i a l E x p o s u r e b y I n i t i a l S y m p t o m O n s e t D a t e 2 4

1 2 . I n i t i a l S y m p t o m O n s e t b y I n i t i a l M e d i c a l E v a l u a t i o n D a t e 2 4

1 3 . S p i l l - R e l a t e d H o s p i t a l A d m i s s i o n s 2 5

14. Dunsmuir City Population and Number (Percent) Reporting Symptoms by Gender and Age 28

15. Dunsmuir Area Population and Number (Percent) Reporting Symptoms by Distance of

H o m e f r o m t h e S a c r a m e n t o R i v e r 2 8

FIGURES

1 . M a p o f A f f e c t e d A r e a 7

2 . A g e a n d G e n d e r D i s t r i b u t i o n o f C a s e s 1 5

3 . D a t e a n d S i t e o f S p i l l - R e l a t e d M e d i c a l E v a l u a t i o n s 1 6

4 . R e s i d e n c e L o c a t i o n o f D u n s m u i r A r e a C a s e s 2 7

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Acute Health Effects of the

Cantara Metam Sodium Spill

An Epidemiologic Assessment

On the evening of July 14, 1991, 19,000 gallons of the herbicide metam sodium were spilled into

the Sacramento River in Northern California as the result of a train derailment. As the chemical travelled

downstream, it killed nearly all aquatic life in its path over an approximately 45-mile segment of the river.

Individuals near the river experienced a variety of symptoms related to exposure to the vapors released

by the chemical. The purpose of this report is to describe health effects of the spill reported to the local

mcdical community for an approximately one-month period immediately following the spill. Public

health implications of the incident and recommendations for further study are also addressed.

B A C K G R O U N D

Description of the Incident

The Sacramento River in Northern California has long been renowned for its beauty and excellent

trout fishing. Originating near Mt. Shasta, it flows southward to Lake Shasta (Figure 1). Human

population along this segment of the river is generally sparse.

On July 14, 1991, at 21:40 hours, a Southern Pacific railroad train consisting of 97 cars and four

locomotives derailed on a tight bridge curve spanning the Sacramento River in a remote area known as

the "Cantara Loop," located approximately six miles north of the town of Dunsmuir. A locomotive, six

empty freight cars, and an unlabeled tank car left the tracks. The tank car fell from the bridge into the

river and came to rest in a partially inverted position in the shallows directly beneath the bridge.

Although the exact cause of the derailment has not been determined, one proposed theory is that

the train may have derailed when one or more of the lead engines momentarily lost and then regained

traction causing a sudden surge. The portion of the train on the curve then may have been pulled tight or

straight with the cars behind it and derailed-a phenomenon termed "stringlining" or "bowstringing."^ It

has also been theorized that the make-up of the train alone (i.e., the order in which cars were linked) may

have been sufficient to cause the bowstringing.

Crew members reported odors coming from the derailed cars shortly after the derailment. By

approximately 21:51, the Dunsmuir clerk and railroad dispatcher's office in Roseville, California had been

a d v i s e d o f t h e d e r a i l m e n t . C r e w m e m b e r s r e v i e w e d t h e t r a i n m a n i f e s t t o d e t e r m i n e t h e c o n t e n t s o f t h e

derailed cars. The tank car, a U.S. Department of Transportation (DOT) 111-A, which has a single 7/16

inch thick steel wall and is the most common type of tank car in use, was not placarded as carrying a

haza rdous subs tance . C on ten ts w e re l i s ted i n the t ra i n man i fes t as " w eed k i l l e r " and i den t i fied an hou r o r

more later as metam sodium.^ The Material Safety Data Sheet (MSDS)^ for the substance was reviewed

and listed the contents as 32.7% metam sodium and 67.3% proprietary or nonhazardous ingredients.

There was little information in the MSDS on procedures for dealing with the release of a large amount of

the substance. Because metam sodium was not officially classified as a hazardous material by the DOT at

Acute Health Effects of Cantara Metam Sodhmi Spill

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the time of the spill, the manifest contained no specific toxicologic information or recommendations in the

event of an accidental release as is required for hazardous materials.

At approximately 04:30 on July 15, Southern Pacific staff who had inspected the site reported a

three by four inch hole in the derailed tank car above the water line which was not leaking. It was

estimated that approximately 1500 gallons of metam sodium might have leaked into the river. As reports

of health effects and dead fish downstream became available later that morning, the extent of the spill

was reevaluated. Reexamination of the tank car revealed two submerged holes in the car at the point

Acute Health Effects ofCantara Metam Sodium Spill

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where it was resting on the river bed.^ At approximately noon on July 15, the extent of the spill was

upgraded to 19,500 gallons, the entire capacity of the tank car.

Because a small amount of metam sodium mixed with river water remained in the tank car at the

time it was pulled from the river on July 16, at 16:30, final estimates have placed the amount of material

actually released into the Sacramento River to be approximately 19,000 gallons of a 32.7% concentrated

solution of metam sodium in water with no other constituents. It is believed that nearly all of the metam

sodium was released during the first hour after the derailment.^

The spilled material was noted to travel en masse southward at approximately 0.5-1.0 mph until

it reached Lake Shasta, 45 miles from the spill site, in the early hours of July 17. Aquatic life along this

section of the river was severely affected. California Department of Fish and Game biologists reported

fish k i l l s in the hundreds o f thousands.

Once the plume entered Lake Shasta, it appeared to remain in a stationary, unbroken mass (it is

not known how much metam sodium remained in this plume). Southern Pacific, hoping to hasten the

dispersal and degradation of the chemical, implemented a previously untested aeration procedure on July

20, which continued through July 30.^ While the effectiveness of the procedure remains unknown, levels

of the primary metam sodium breakdown product in lake water samples were below detection levels by

July 29.

The largest population center on the affected segment of the river is the town of Dunsmuir

(population 2129, 1990 census)" , located six miles downstream from the spill (Figure 1). Several much

smaller communities (Castella, Sweetbrier, La Moine, Pollard Flats, Delta, and Lakehead) are located

farther downstream. In addition, there are several campgrounds located along this segment of the river.

By 06:00 on July 15, the county health department had logged complaints from Dunsmuir

residents of irritated eyes and unpleasant odors from the river. The tail-end of a light yellow green plume

was reported to pass through Dunsmuir around 07:45.^ Mt. Shasta Mercy Hospital, located a few miles to

the north of the spill site, began seeing exposure-related illnesses in its emergency room by 11:(X) on July

15 .

At approximately 11:30 on July 15, the city manager of Dunsmuir ordered the Dunsmuir Police

Department to begin a mandatory evacuation of the town. This was downgraded to a voluntary

evacuation order approximately one hour later and remained in effect until July 19. At 14:00 on July 15, a

temporary shelter for voluntary evacuees was established at the Dunsmuir High School, located on a hill

approximately 1500 feet from the river. The shelter remained open until 20:(X) on July 20. Paramedics

were stationed at the shelter to assess, treat, and triage health complaints.

Toxicology of Metam Sodium and Byproducts

D E S C R I P T I O N O F C O M P O U N D A N D B Y P R O D U C T S

Metam sodium (also known as sodium methyldithiocarbamate), molecular formula C2H4NS2Na,

is most commonly used as a soil fumigant which is added to fields as an aqueous solution prior to

planting crops in order to control nematodes, soil fungi, weeds, weed seeds, and soil insects. Agricultural

use of metam sodium has increased dramatically in recent years since other previously used fumigants,

such as 1,3 dichloroprof)ene (Telone), were removed from the market because of health concerns. An

estimated 7 to 12 million pounds of metam sodium are used annually in the U.S.; among the 50 states,

California accounts for the largest percentage of use.^'^ It is typically applied to soil at rates of up to 300

lbs per acre. Because pure metam sodium in white crystalline solid form is unstable, it is normally

transported in a concentrated solution in water for commercial use.^


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Metam sodium in this form is essentially non-volatile. Upon further dilution with water, (as

would occur when applied to moist soil), it is believed to rapidly decompose to the volatile compounds,

methyl isothiocyanate (MITC), which is the major biocidal byproduct, and hydrogen sulfide (H2S). Other

potential, albeit less common, byproducts include methylamine and carbon disulfide. '

MITC is expected to volatilize completely from treated soil within two to three weeks after appli

cation. Because MITC is highly water soluble, it has the potential to leach into groundwater. In aquatic

environments, it is not expected to bio-concentrate in aquatic organisms or adsorb to sediment or

suspended organic matter.

E X P O S U R E E F F E C T S

Acute effects: Given metam sodium's rapid decomposition upon dilution with water, the

potential for exposure to the parent comp>ound was expected to be minimal. Both MITC and H2S, the two

main byproduct gases, are chemical irritants. For H2S, a gas which can occur naturally, exfxjsure effects

are better known. Low concentrations of H2S in the range of 10 - 200 parts per million (ppm) can cause

localized eye and respiratory tract irritation. Higher concentrations may produce systemic symptoms

such as nausea, vomiting, diarrhea, headache, dizziness, confusion, weakness, tachypnea, tachycardia,

cardiac arrhythmia and sweating.^ MITC is known to be extremely irritating to skin and mucous mem

branes and at much lower concentrations than Although other acute health effects of MITC

exposure in humans are less well described, the health effects would appear to be similar to those seen

with H2S exposure based on limited data from animal studies and case reports of occupational

exposure.' Metam sodium is a thiocarbamate and, unlike carbamate and organophosphate pesticides,

does not significantly inhibit cholinesterase.

An important difference between the two compounds is the relationship between their odor and

irritant threshold concentrations as shown in Tabic 1. MITC can cause symptoms at concentrations not

normally detected by the sense of smell. In contrast, H2S can be smelled at levels much less than those

necessary to produce irritant symptoms.

MITC should not be confused with methyl isocyanate (MIC), the substance released during a

1984 industrial accident in Bhopal, India, in which over 2000 deaths and 200,000 injuries were reported.

Although MITC and MIC are structurally related and both are chemical irritants, they are distinct

chemicals with different toxicologic properties. Also, toxicologic evidence suggests MIC concentrations

were several thousand times higher in Bhopal than expected MITC concentrations from the Cantara

incident. Thus, observed exposure effects in Bhopal can not be directly translated to MITC.

TABLE 1. odor and I r r i tan t Thresho lds o f Metam Sodium Breakdown

P r o d u c t s

C O M P O U N D

C H A R A C T E R I S T I C M I T C H 2 S R e f e r e n c e s

O d o r h o r s e r a d i s h r o t t e n e g g s 1 0 , 1 1

O d o r t h r e s h o l d * l O O p p b 1 p p b 1 1 , 1 2

I r r i t a n t t h r e s h o l d * 7 0 p p b 1 0 , 0 0 0 p p b 7 , 1 2

* Lowest reported valuesthresholds may vary considerably from person to person.

ppb = parts per billion

Acute Health Effects of Cantara hAetam Sodium Spill

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Chronic Effects: Other health effects from exposure to metam sodium or MITC have not been

well-defined. Because a number of required laboratory animal studies have not yet been completed,

specific data on carcinogenic, reproductive, and other chronic effects are incomplete. '* Information which

i s k n o w n i s s u m m a r i z e d b e l o w :

Carcinogenicity: Studies of MITC for carcinogenicity in rats and mice have been negative.

Metam sodium itself has not been examined in a long-term study for cancer end-p>oints.'

Teratogenicity: Based on published data by the California Department of Food and Agriculture

(CDFA), it was initially believed that there were no teratogenic effects from exposure to metam sodium or

its byproducts. However, further review of information contained in CDFA's proprietary data files by

California Environmental Protection Agency (Cal-EPA) staff indicated that metam sodium may be a

teratogen, producing neural tube defects in rats and rabbits at high doses. At levels which showed

minimal maternal toxicity, MITC administration was associated with fetal growth retardation in rabbits.

Effects on humans are unknown. MITC is currently being tested for teratogenicity.

Chronic respiratory effects: Individuals exposed to irritant gases similar to MITC occasionally

have been shown to develop prolonged bronchial hyper-responsiveness (i.e., reactive airway dysfunction

syndrome or RADS) following an initial chemical bronchitis.^^

DHS-EETP Response to the Incident

I N I T I A L R E S P O N S E

Both Siskiyou and Shasta Counties were affected by the spill since the county line crosses the

affected river segment just south of Dunsmuir. There were considerable challenges in coordinating the

emergency response across both counties. A command post was established at the Siskiyou County

Sheriffs Department substation in the city of Mt. Shasta, less than five miles north of the spill site. Central

management operations, which included most state agency representatives, were located at the California

Department of Forestry (CDF) Ranger Office in Redding, approximately 60 miles south of the spill site.

The California Department of Fish and Game (CDFG) was the lead agency in responding to the incident.

Over 50 federal, state, county, and local agencies ultimately became involved at some point in the first

week following the incident.

The California Department of Health Services (DHS) became aware of the incident at

approximately 08:00 on July 15. Later that afternoon, staff from the DHS Hazard Identification and Risk

Assessment Branch (HIRAB) were dispatched to the incident site to provide medical, toxicologic, and

epidemiologic support to the local health departments and to document the event (HIRAB officially

became part of the newly-formed Cal-EPA on July 17,1991). On July 17, as the magnitude of the incident

became more apparent, additional staff from the DHS Environmental Epidemiology and Toxicology

Program (EETP) and physicians from the DHS Preventive Medicine Residency Program were sent to aid

in the epidemiologic investigation and remained through July 20.

EPIDEMIOLOGIC INVESTIGATION OBJECTIVES

In the early phases of the incident, several unknown variables complicated predicting the

potential health effects of the spill. The exact composition of the tank car contents, including the

possibility of unidentified toxic constituents in the metam sodium solution, was not immediately known.

Although prior laboratory data and limited occupational rep>orts provided an indication of the probable

environmental fate and potential health effects, the chemical behavior of such a large quantity of metam

sodium in a dynamic, non-laboratory environment could not be predicted with certainty. There were no

pre-established "off-the-shelf" guidelines for measuring metam sodium or MITC in the environment.

Acute Health Effects of Cantara Metam Sodium Spill

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Reliable MITC air sampling methods and equipment, which could quantify the exposures that were

occurring, were not in place until July 17, more than two days after the spill. Furthermore, there was a

one to three day turn-around time for laboratory reports on MITC air levels.

Therefore, the first objective of the epidemiologic investigation was to quickly determine the

immediate risk to public health and the extent of health effects from the spill. Activities in this area have

been described previously. To briefly summarize, telephone calls and on-site visits to area hospitals

and the shelter facility were made from July 15 to July 20. Health care providers at these sites were

interviewed regarding the number of spill-related patients evaluated and the types and severity of

symptoms they had seen. Patient medical charts were reviewed. Reported symptoms were assessed for

consistency with known toxicologic end-points of metam sodium and were examined for evidence of

exposure to unexpected substances. This rapid assessment indicated that: 1) a substantial number of

individuals reported symptoms from the spillmost of which did not require hospitalization; 2) there

were no fatalities as a result of the spill; and 3) reported symptoms were generally consistent with

exposure to irritant vapors such as those expected to be produced from decomposition of metam sodium.

A second objective of the investigation was to more formally document and analyze spill-related

health effects reported to the local medical community and occurring within the first month after the

incident. Information from such a study could be used to define better the toxicology of this relatively

unstudied chemical and more fully gauge the total acute health impact of the incident. Methods and

findings of this analysis are described below.

M E T H O D S

We examined spill-related health effects reported from July 14 through August 16, 1991, from

either the temporary evacuation and triage shelter in Dunsmuir, private physicians in the Dunsmuir/Mt.

Shasta region, or area hospitals. For each of these information sources, cases were defined as persons

reporting symptoms during the period of study which they believed were secondary to the spill.

Exposure was based on self-report. Cases could potentially include area residents, tourists, or individuals

traveling through the affected area who sought medical evaluation at one of the information sources.

D a t a C o l l e c t i o n I n s t r u m e n t s

A one-page, self-administered questionnaire for patients was designed by DHS staff and

distributed to both the shelter and the Mount Shasta emergency room on July 15. In addition to name,

gender, age, address, and date completed, the questionnaire contained a list of possible symptoms based

on known metam sodium toxicology which could be checked or circled. A space to write in any other

symptoms which may have been experienced was provided. The questionnaire also asked respondents

to describe any odors they smelled and the location, time, and duration of their exposure. The original

questionnaire form was revised slightly during the first week after the spill to include a more complete

list of possible symptoms and facilitate easier completion by respondents.

Pesticide Illness Reports (PlR's) were a second data collection instrument. These are one-page

forms which must be completed by any California physician who examines a patient with health

problems suspected to be pesticide related. The forms are submitted to both the County Health Officer

and the State. Items on the form include the patient's name, gender, age, and address, date of evaluation,

and date, time, location, and route of exposure. Physicians are also asked to briefly describe symptoms,

physical findings, treatment, and indicate if the patient was pregnant at the time of exposure.


11


13/37

A single abstraction form was designed to extract data from the questionnaires, PIR's and

hospital patient records. Information which could be captured by the abstraction form included patient

demographics, symptoms, physical findings, test results, treatment, and exposure history. The

abstraction form was prepared in an Epi Info computer database for direct key entry of records when

possible. The procedures for obtaining the information from each of the three sources are described

b e l o w .

D a t a S o u r c e s

1. Dunsmuir Shelter: Individuals using the Dunsmuir shelter triage facility during its period of

operation from July 15-20, were encouraged by shelter staff to complete the questionnaire. Parents were

asked to complete the questionnaire for young children. Questionnaires were collected by shelter staff

and later returned to DHS. In addition, DHS was permitted to review a separate index card file which

shelter paramedics had maintained for all patient contacts. Questionnaires were supplemented with

paramedic data when possible to complete the case profile.

2. Local Physicians: DHS obtained copies of all spill-related PIR's for the study period which had

been received by the Siskiyou County Environmental Health Department through September, 1991.

3. Hospital data: Three hospitals (Mercy Hospital in Mt. Shasta, Mercy Hospital in Redding, and

the Redding Medical Center) were identified within 25 miles of the affected river segment and thus were

presumed most likely to see spill-related illnesses. On July 15 and 16, DHS contacted each hospital by

telephone regarding spill-related patient contacts. DHS requested access to all emergency room and

inpatient medical records of patients identified by hospital staff as being spill-related. Mt. Shasta Mercy

Hospital staff agreed to distribute and collect questionnaire forms identical to those distributed at the

shelter. Patients voluntarily completed the questionnaire while waiting for evaluation. If completed,

questionnaires were included in the patient's permanent medical record and used by abstractors to

supplement information provided by the attending physician. Two-person teams abstracted records on-

site at each of the three hospitals during the first week after the spill.

Once the field investigation team left on July 20, Mt. Shasta Mercy Hospital was contacted daily

by telephone through August 16 to monitor the number of spill-related patients being seen. Because the

two hospitals in Redding reported very few spill-related patient contacts during the first week after the

spill, they were not surveyed after July 19. The remaining spill-related patient charts for the study period

from Mt. Shasta Mercy Hospital were abstracted on-site in August.

Data Analysis

Once all records were entered into a single Epi Info database, they were reviewed for duplicates.

Some individuals had records abstracted from multiple sources. If the recorded visits for the same person

occurred on different days, they were considered separate records regardless of the reporting source. If

the visits to different reporting sources occurred on the same day, it was usually the result of paramedics

at the shelter triaging patients to either local physicians' offices or to the Mount Shasta emergency room.

Thus, these visits were considered to represent a theoretical single visit for which information provided

by paramedics and attending nurses and physicians was combined. Any discrepancies in the information

provided by the different reporting sources were individually inspected, resolved where the correct

information was clear (e.g, key entry error) and, in the few cases of continued confusion, resolved in favor

of the emergency room or private physician record.


1 2


14/37

Data were analyzed by date and site of evaluation, age, gender, and city of residence.

Frequencies of reported odors and symptoms were calculated. Symptoms were stratified by age, sex,

evaluation site, date of evaluation, odor detection, and smoking history. A one-way analysis of variance

or Student's t-test was used to determine whether the average number of symptoms reported per case

differed for any of the stratified variables. Relation of symptom onset to exposure date and evaluation

da te w as a l so exami ned .

All hospitalizations and pregnancies identified through the surveillance were reviewed. In

October, DHS staff conducted a telephone follow-up survey of women identified as pregnant at the time

of the spill. This survey included questions on past pregnancy history, number of weeks pregnant at the

time of the spill, progress of pregnancy since the spill, and pregnancy outcome.

An exposure assessment analysis of cases reporting their city of residence as Dunsmuir was

performed because: 1) Dunsmuir was the largest community affected by the spill; 2) it was located

closest to the spill and therefore, presumably had the highest contaminant levels; 3) it straddles the

Sacramento River so that nearly all residents are located within a short distance of the river and were

theoretically at risk of exposure; 4) its location 6 miles from the spill site meant that the leading edge of

the spill plume would have reached the city sometime in the early morning of July 15-a time when most

residents would be expected to be at home; and 5) 1990 census data gives a relatively current estimate of

the population at risk so that rates of illness could be calculated.

Exposure assessment for individual cases was limited by the absence of environmental

monitoring data for the first 2 days after the spill. As a surrogate for exposure, distance of the exposure

site from the river was examined in relation to symptom reporting and attack rates for Dunsmuir

residents. The primary exposures for Dunsmuir residents were assumed to have occurred at home on the

morning of July 15.

A map of the Dunsmuir area showing the location of city limits, major streets and highways, and

the Sacramento River, was produced using the computer program ARC/lnfo.^^ Home addresses of cases

listing their city of residence as Dunsmuir were determined using database information. For those cases

in which a street address was not given (i.e. missing or P.O. Box), a 1991 telephone directory of the area

was consulted. As a final method of determining home address, the Dunsmuir post office was contacted

to provide a street address. Cases in which the street address could not be located were excluded. Case

residences then were geo-coded and plotted on the Dunsmuir map.

Rates of illness were calculated for the Dunsmuir population and stratified by age and gender

using only those cases who actually lived within the city limits as the numerator and 1990 census data as

t h e d e n o m i n a t o r .

To examine the association between residential distance from the river and symptom reporting,

we created 300 foot concentric regions or zones around the river. Because of the irregular city

boundaries, the zones included some areas outside the city limits. Zones were also extended

approximately one-half mile past the southern city boundary to include those cases who reported their

city of residence as Dunsmuir but lived just south of the city limits. Populations of each zone were

determined from census block data. Where a block crossed two or more zones, the proportion of the

block population in the zone was presumed equal to the proportion of the block's housing units located

wi th in that zone. Rates o f i l l ness were ca lcu la ted and contrasted for each zone.

Acute Health Effects of Cantara Metarn Sodium Spill

1 3


15/37

R E S U L T S

D a t a S o u r c e s

Information was obtained for 848 medical visits that were related to the spill from July 15 through

August 16,1991. There were a total of 705 separate individuals with 115 seeking medical attention more

than once (89 seen twice, 24 seen three times, and 2 seen four times). The number of medical evaluations

were approximately equally distributed between the triage center, physicians' offices and emergency

rooms (Table 2).

Of the 278 emergency room visits recorded, 257 (92.4%) occurred at Mt. Shasta Mercy Hospital;

13 (4.7%) occurred at the Redding Medical Center; and 8 (2.9%) occurred at Redding Mercy Hospital.

Information from 223 visits to private physicians in the area was primarily obtained from pesticide illness

reports which were received from 17 different providers.

The total number of shelter evaluations (361) is slightly lower than that previously reported by

shelter staff. Data arc missing for those individuals who did not complete questionnaires. A total of 23

individuals evaluated at the shelter sought additional evaluation from emergency rooms or private

physicians.

TABLE 2. Site of Spill-Related Medical Evaluation

N U M B E R O F E V A L U A T I O N S

Emergency Room

M D O f fi c e

Shelter Only

U n k n o w n

R e p e a t

Includes 19 initially seen at shelter.

Includes 4 initially seen at shelter.

TABLE 3. City of Res-idence for Cases

N U MB E R O F C A S E S

D u n s m u i r

M t . S h a s t a

C a s t e l l a

L a k e h e a d

Other (


16/37

Characteristics of Cases

As shown in Table 3, the majority of individuals who sought medical attention were from the

communities of Dunsmuir (70.6%), Mt. Shasta (7.2%), and Castella (6.4%), which were the three

communities closest to the spill site. The age and gender distribution of those reporting symptoms are

shown in Figure 2. For each age group, more females than males reported symptoms, particularly for

those between age 20 and 39. Overall, 54.3% of the individuals reporting symptoms were female. Of

individuals reporting symptoms, the largest numbers were seen in the 30-39 age group.

Figure 3 shows the number of spill-related medical visits by both date and site of evaluation. The

number of visits remained relatively constant from July 15 to 19, decreased sharply on Saturday, July 20,

and gradually tapered off during the second post-spill week. A small increase in the number of visits was

noted on Monday, July 29. There were 28 additional visits from August 1 to 16.


15


17/37

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18/37

S Y M P T O M S

Symptoms most commonly reported at first evaluation by individuals seeking medical attention

are shown for each evaluation site in Table 5. The symptoms reported at each site were generally similar.

Overall, the most common symptom reported was headache (63.8%); nearly half of the individuals

evaluated complained of eye irritation and/or nausea. Symptoms represented in the "other" category

included: depression, disorientation, drowsiness, dry mouth, earache, fatigue, fever, hot flashes,

irritability, memory reduction, nose bleed, numbness, pain in the arms or legs, ringing in the ears, and

sweating. Each of these symptoms was reported by fewer than 5% of the cases.

A significantly (p < .05) higher percentage of emergency room patients reported dizziness,

weakness, eye irritation, nausea, vomiting, respiratory symptoms (shortness of breath, chest tightness,

cough and wheeze), metallic taste, nervousness, flushing and chills. The average number of symptoms

reported by each case was also significantly higher for emergency room patients than for private

physician or shelter patients.

As shown in Table 6, the distribution of symptoms varied little by gender. Females reported a

significantly higher percentage of diarrhea and nervousness. There was not a significant difference

between males and females in the mean number of symptoms reported per case.

Types of symptoms reported by age groups are shown in Table 7. Distribution of symptoms was

generally similar for each age group. There were significantly fewer symptoms per person on average for

those less than 20 and greater than 69 years of age.

Table 8 compares the types of symptoms reported for cases 10 years of age or older based on

whether an odor was reported. A total of 227 cases reported smelling an odor while 49 reported smelling

no odor. A large number of cases (282) did not have any data regarding odor detection. The frequency of

headache was significantly higher among those reporting an odor; the frequency of weakness,

nervousness, and flushing was significantly higher among those reporting no odor. Otherwise, the

distribution of symptoms was generally similar. The mean number of symptoms p>cr case was not

significantly different based on odor detection status.

Table 9 compares the type of symptoms reported by smoking status. Data on smoking status was

limited. A total of 75 cases were recorded as current smokers while 48 specifically reported they did not

smoke. There were 435 cases in which this data was missing. The distribution of symptoms was similar

based on smoking status although, for nearly all symptoms, the frequencies were lower in the non-

smokers. The only symptom in which this difference was statistically significant was shortness of breath.

The mean number of symptoms per case was higher for smokers but not statistically significant.

Acute Health Effects ofCantara Metam Sodium Spill 1 7


19/37

TABLE 5. Number (Percent) of Cases Reporting Selected Symptoms

S I T E

Emergency Room

Private Physician S h e l t e r

T o t a l

S Y M P T O M n = 2 1 9

n = 171 n = 30 7

p-va lue

N = 697

N e u r o l o g i c

h e a d a c h e 1 3 5 ( 6 1 . 6 ) 104 (60.8) 206 (67.1) 0 . 2 7

445 (63.8)

d i z z i n e s s 8 6 ( 3 9 . 3 ) 31 (18.1) 89 (29.0) < 0 . 0 1

206 (29.6)

w e a k n e s s 5 0 ( 2 2 . 8 ) 6 (3.5)

25 (8.1) < 0 . 0 1 81 (11.6)

M u c o m e m b r a n o u s I r r i t a t i o n

e y e 1 2 3 ( 5 6 . 2 )

77 (45.0)

138 (45.0) 0 . 0 2 338 (48.5)

t h r o a t 1 0 4 ( 4 7 . 5 ) 68 (39.8) 121 (39.4) 0 . 1 4 293 (42.0)

n a s a l 5 1 ( 2 3 . 3 ) 37 (21.6) 73 (23.8) 0 . 8 7 161 (23.1)

G a s t r o i n t e s t i n a l

n a u s e a 1 1 6 ( 5 3 . 0 )

84 (49.1) 122 (39.7) 0 . 0 1 322 (46.2)

d i a r r h e a 5 5 ( 2 5 . 1 )

51 (29.8) 70 (22.8) 0 . 2 4 176 (25.3)

a b d o m i n a l p a i n 4 8 ( 2 1 . 9 )

37 (21.6) 46 (15.0) 0 . 0 7 131 (18.8)

v o m i t i n g 4 9 ( 2 2 . 4 )

26 (15.2) 29 (9.4) < 0 . 0 1

104 (14.9)

R e s p i r a t o r y

s h o r t n e s s o f b r e a t h 7 7 ( 3 5 . 2 ) 30 (17.5) 82 (26.7)

< 0 . 0 1

189 (27.1)

c h e s t t i g h t n e s s 6 7 ( 3 0 . 6 ) 26 (15.2) 63 (20.5) < 0 . 0 1

156 (22.4)

c o u g h 6 7 ( 3 0 . 6 )

13 (7.6) 17 (5.5) < 0 . 0 1

97 (13.9)

w h e e z e 3 2 ( 1 4 . 6 ) 17 (9.9) 32 (10.4)

< 0 . 0 1 81 (11.6)

D e r m a t o l o g i c

r a s h 3 0 ( 1 3 . 7 ) 32 (18.7) 33 (10.7) 0 . 0 5

95 (13.6)

i t c h i n g 3 2 ( 1 4 . 6 )

14 (08.2)

32(10.4)

0 . 1 2 78 (11.2)

M i s c e l l a n e o u s

m e t a l l i c / o d d t a s t e 3 2 ( 1 4 . 6 ) 2 (1.2)

16 (5.2) < 0 . 0 1 50 (7.2)

n e r v o u s 1 7 ( 1 7 . 8 ) 5 (2.9)

11 (3.6) 0 . 0 4 33 (4.7)

fl u s h i n g 2 1 ( 9 . 6 )

1 (0.6) 9 (2.9) < 0 . 0 1

31 (4.4)

c h i l l s 1 4 ( 6 . 4 ) 4 (2.3) 4 (1.3) < 0 . 0 1 22 (3.2)

o t h e r 8 9 ( 4 0 . 6 ) 84 (49.1) 91 (29.6) < 0 . 0 1 264 (37.9)

Mean number of

s y m p t o m s p e r c a s e 5 . 9

4 . 4 4 . 3 < 0 . 0 1 4 . 8

A Pearson chi square was used to compare proportions of patients reporting symptoms by sites; an

analysis of variance was used to compare mean number of symptoms by site.

' S i te i nde te rmina te fo r 8 cases .

Acute Health Effects ofCantara Metarn Sodium Spill

18


20/37

Number (Percent) of Cases Reporting Selected

Symptoms by Gender

GENDER*

SYMPTOM

N e u r o l o g i c

h e a d a c h e

dizz iness

w e a k n e s s



d i a r rhea

abdominal pain

vomiting


s h o r t n e s s o f b r e a t h

chest tightness

cough

w h e e z e


itching


metal l ic/odd taste

lushing

F e m a l e

n = 379

250 (66.0)

124 (32.7)

41 (10.8)

182 (48.0)

170 (44.9)

91 (24.0)

184 (48.5)

113(29.8)

74(19.5)

63 (16.6)

100 (26.4)

90 (23.7)

51 (13.5)

42 (11.1)

50 (13.2)

47(12.4)

31 (8.2)

13 (3.4)

19 (5.0)

12 (3.2)

150 (39.6)

n = 319

198 (62.1)

85 (26.6)

40 (12.5)

160 (50.2)

126 (39.5)

75 (23.5)

140 (43.9)

66 (20.7)

57(17.9)

41 (12.9)

91 (28.3)

68 (21.3)

46 (14.4)

42 (13.2)

47 (14.3)

31 (9.7)

20 (6.3)

21 (6.6)

12 (3.8)

10 (3.1)

116(36.4)

p-value~

Mean number ot

s y m p t o m s p e r c a s e 5 ^ 0 4 7 0 . 2 2

Gender unknown for 7 cases.

^ A Pearson chi square was used to compare proportions of patients reporting

symptoms by gender; a Student t-test was used to compare the mean number of

symptoms by sex.

Acute Health Effects of Cantara Metarn Sodium Spill

19


21/37

Table 7. Percent of Cases Reporting Selected Symptoms by 10-year Age Groups

AGE (years)*

0 - 9 1 0 - 1 9 2 0 - 2 9 3 0 - 3 9 4 0 - 4 9 5 0 - 5 9 6 0 - 6 9 70 +

n = 1 0 1 n = 1 0 2

n = 8 1 n = 1 4 7 n = 1 1 6 n = 5 2 n = 3 9

n = 2 1

S Y M P T O M

(%) (%) (%) (%) (%) (%) (%) (%)

p-value"'"

N e u r o l o g i c

h e a d a c h e 3 2 . 7 6 4 . 7 7 7 . 8 7 4 . 1

7 7 . 6

5 7 . 7 6 9 . 2

4 7 . 6 < 0 . 0 1

d i zz i ness

9 . 9 2 1 . 6 3 9 . 5

3 8 . 1 3 9 . 7 3 4 . 6 2 3 . 1

3 3 . 3 < 0 . 0 1

w e a k n e s s 7 . 9 6 . 9

1 8 . 5 1 0 . 9

1 2 . 9

1 3 . 5 2 0 . 5 1 4 . 3

0 . 1 6

M u c om e m br a n ou s I r r i t a t i o n

eye

3 8 . 6

4 7 . 1 5 1 . 9 4 9 . 0 5 1 . 7 4 8 . 1

6 6 . 7

5 2 . 4 0 . 1 8

t h r o a t

2 3 . 8 3 2 . 4 5 3 . 1 5 3 . 7 4 9 . 1 5 1 . 9 4 6 . 2 2 8 . 6 < 0 . 0 1

n a s a l

1 7 . 8 2 5 . 6 2 5 . 9 2 9 . 3 2 6 . 7 2 6 . 9 2 5 . 6 1 9 . 0 0 . 5 4


n a u s e a

2 9 . 7 4 6 . 1 5 8 . 0 5 1 . 0 5 1 . 7 5 0 . 0 4 3 . 6 1 4 . 3 < 0 . 0 1

d i a r r h e a 2 7 . 7 1 7 . 6 2 7 . 2 3 4 . 7 3 1 . 9 2 3 . 1 1 7 . 9 4 . 8 0 . 0 1

abdominal pain 1 6 . 8

2 0 . 6 2 3 . 5 1 6 . 3 1 3 . 8 2 3 . 1 1 5 . 4 9 . 5 0 . 3 6

vomiting

1 5 . 8 7 . 8 2 3 . 5 1 6 . 3 1 3 . 8 2 1 . 2 1 0 . 3 0 . 0 0 . 0 4


s h o r t n e s s

o f b r e a t h

7 . 9 1 1 . 8 3 3 . 3 3 3 . 3 3 5 . 3 5 0 . 0 3 5 . 9 2 3 . 8 < 0 . 0 1

chest tightness

4 . 0 1 2 . 7 3 0 . 9 2 7 . 2 3 2 . 8 3 2 . 7 3 0 . 8 2 3 . 8 < 0 . 0 1

cough

1 4 . 9 8 . 8 1 9 . 8 1 3 . 6 1 3 . 8 1 5 . 4 2 8 . 2 4 , 8 0 . 1 0

w h e e z e 7 . 9 3 . 9

1 6 . 0 1 7 . 0 1 4 . 7 1 9 . 2 1 7 . 9 0 . 0

0 . 0 1


r a s h 1 2 . 9 1 3 . 7 1 4 . 8

1 5 . 0 1 2 . 9 1 3 . 5 1 2 . 8

1 9 . 0 0 . 9 9

itching

5 . 9 8 . 8 1 4 . 8 1 1 . 6 12.9 17.3 1 0 . 3 9 . 5 0 . 4 4


m e t a l l i c / o d d

t a s t e 1 . 0 1 . 0 9 . 9 8 . 8 1 1 . 2 1 1 . 5 1 7 . 9 4 . 8 < 0 . 0 1

n e r v o u s

3 . 0 1 . 0 3 . 7 6 . 8

6 . 9 3 . 8

1 5 . 4 4 . 8 0 . 0 4

flushing

3 . 0 1 . 0 6 . 2 4 . 1 4 . 3 3 . 8 1 2 . 8 4 . 8 0 . 2 0

c h i l l s 2 . 0 0 . 0 4 . 9

5 . 4 1 . 7 5 . 8 5 . 1 0 . 0 0 . 1 8

o t h e r 3 7 . 6 1 9 . 6

3 7 . 0 4 2 . 9 4 8 . 3 4 4 . 2 4 1 . 0 5 2 . 4 < 0 . 0 1

Mean number

of symptoms

p e r c a s e

3 . 2 3 . 7 6 . 0 5 . 7 5 . 7 5 . 7 5 . 8 3 . 8 < 0 . 0 1

* Age unknown for 46 cases.

A Pearson chi square was used to compare proportion of patients reporting symptoms by age; an analysis of variance was

used to compare the mean number of symptoms by age group

Acute Health Effects of Cantara Metam

Sodium Spill 2 0


22/37

TABLE 8. Number (Percent) of Cases Reporting Selected Symptoms by

Odor Detec t ion S ta tus

O D O R D E T E C T I O N S T A T U S

SYMPTOM

N e u r o l o g i c

h e a d a c h e

dizz iness

w e a k n e s s



n a u s e a

d i a r rhea

abdominal pain

vomiting



chest tightness

cough

w h e e z e

Dermatol OGic

r a s h

itching


metal l ic/odd taste

n e r v o u s

flushing

M e a n n u m b e r o f

s y m p t o m s p e r c a s e

n = 227

191 (84.1)

109 (48.0)

41 (18.1)

155 (68.3)

142 (62.6)

101 (44.5)

135 (59.5)

86 (37.9)

61 (26.9)

40(17.6)

92 (40.5)

81 (35.7)

39 (17.2)

49 (21.6)

37 (16.3)

28 (12.3)

34 (15.0)

16 (7.0)

15 (6.6)

10 (4.4)

97 (42.7)

n = 4 9

33 (67.3)

22 (44.9)

20 (40.8)

30 (61.2)

26 (53.1)

19 (38.8)

30 (61.2)

13 (26.5)

14(28.6)

8 (16.3)

22 (44.9)

17(34.7)

13 (26.5)

12 (24.5)

9(18.4)

11 (22.4)

7(14.3)

11 (22.4)

9 (18.4)

4 (8.2)

17(34.7)

p -va l ue '

Excludes cases


23/37

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24/37

T A B L E 1 0 .

Number (Percent) of All Visits in Which Selected Symptoms are

Reported by Date Evaluated

DATE SEEN

SYMPTOM

N e u r o l c x s i c

h e a d a c h e

d i z z i n e s s

w e a k n e s s



d i a r r h e a

abdominal pain

vomiting



chest tightness

cough

w h e e z e

Dermatol oGic

itching


m e t a l l i c / o d d t a s t e

n = 564

364 (64.5)

177 (31.4)

58 (10.3)

272 (48.2)

224 (39.7)

123 (21.8)

254 (45.0)

138 (24.5)

105 (18.6)

80(14.2)

163 (28.9)

143 (25.4)

72 (12.8)

64(11.3)

72 (12.8)

63 (11.2)

33 (6.2)

30 (5.3)

27 (4.8)

19 (3.4)

193 (34.2)

7 / 2 2 - 8 / 1 6

n = 247

163 (66.0)

64 (25.9)

39 (15.8)

120 (48.6)

108 (43.7)

56 (22.7)

120 (48.6)

84 (34.0)

60 (24.3)

46 (18.6)

65 (26.3)

54 (21.9)

49 (19.8)

39(15.8)

50 (20.2)

25 (10.1)

24 (9.7)

14 (5.7)

14 (5.7)

8 (3.2)

131 (53.0)

fl u s h i n g 2 7 ( 4 . 8 ) 1 4 ( 5 . 7 ) 0 . 6 0

c h i l l s 1 9 ( 3 . 4 ) 8 ( 3 . 2 ) 0 . 9 2

o t h e r 1 9 3 ( 3 4 . 2 ) 1 3 1 ( 5 3 . 0 ) < 0 . 0 1

Mean Number of

s y m p t o m s p e r v i s i t 4 8 5 4 0 . 0 1

Evaluation date unknown for 37 cases.

A Pearson chi square was used to compare the proportion of patients reporting symptoms by date

seen; a Student t-test was used to compare the mean number of symptoms by date.

C H R O N O L O G Y O F S Y M P T O M S

An unexpected finding was the continued reporting of health complaints a week or more after

the spill. Table 10 compares the types of symptoms reported during the first week after the spill to those

reported a week or more later. Significantly higher percentages of weakness, diarrhea, cough, rash, and



25/37

other symptoms were reported among those seen later. The remaining symptoms showed little

difference in distribution between the two groups.

Table 11 compares initial exposure and symptom onset date. For those cases in which exposure

and symptom onset date were known, 212 (57.8%) of individuals reported initial symptoms and exposure

occurred July 15. A total of 314 (85.6%) reported symptom onset within one day after exposure, 24 (6.5%)

reported symptom onset two days after exposure, and 29 (7.9%) reported symptom onset three or more

days after exposure.

Table 12 compares the initial symptom onset date to the date of first evaluation. For those in

which this information was complete, 130 (27.9%) sought evaluation within one day of symptom onset

while 113 (24.3%) delayed evaluation for seven or more days after symptom onset.

Table 11. Initial Exposure by Initial Symptom Onset Date

EXPOSURE DATE (July)

S Y M P T O M

DATE (July) 1 4

1 5 1 6

1 4 7

1 5 2 8 2 1 2

1 6 1 3 3 1 3

1 7 2 1 3 2

1 8 1 8 4

1 9 0 8 0

2 0 0

1

0

2 1 0 2 0

2 2 - 2 5 1 4

2

T o t a l 4 0 2 8 1 2 1

Exposure date not given for 127 cases. Symptom onset date not given for 45 cases. Neither exposure nor symptom

onset date given for 166 cases.

Table 12. Initial Symptom Onset by Initial Medical Evaluation Date

SYMPTOM DATE (July)

EVALUATION

D A T E ( J u l v ) 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1

1 4 0

7 / 2 2 - 8 / 1 6

1 5 0 4 7 4 7

1 6 0 2 1 4 2 5

1 7 1 3 3 1 1 8 5 3

1 8 1 3 7 1 0 4 5 5 7

1 9 1 4 0 9 1 2 6 1 2 8 0

2 0 0 1 9

5

4

4

4

2

3 8

2 1 1

5 4 1 2 2 1 0 1 6

7 /22 -8 /16 6 8 8 1 6 5 3 4 8 3 1 5 1 4 8

Tota l 1 0 2 9 1 5 9 3 4 2 0 2 2 11 1 8 1 5 465'

Symptom onset not given for 202 cases. Evaluation date not given for 29 cases, Neitfier symptom onset nor

evaluation date given for 9 cases.


2 4


26/37

Hospitalizations

A total of seven individuals were admitted to Mt. Shasta Mercy Hospital during the first week

after the spill for possible exposure related illness. A summary of these patients is shown in Table 13.

There were four respiratory-related admissions, and two cases of possible syncope (fainting). Cardiac

arrhythmia (bigeminy) and disorientation were noted in one individual who probably received a

particularly intense exposure through involvement in initial clean-up activities at the spill site . All

patients were discharged by July 28. There were no other known spill-related hospital admissions in the

area. There were no human fatalities due to the spill.

TABLE 13. Spill-Related Hospital Admissions (Mt. Shasta Mercy Hospital)

A D M I T D I S C H A R G E

C A S E / S E X / A G E

1 / F / 3 4

2 / M / 3 6

D I S C H A R G E D I A G N O S E S

Syncope, headache, light headedness,

abdominal cramps with nausea and

vomiting

PVO's* with bigeminy, respiratory

distress, probable mucosal irritation,

h e a d a c h e

3 / F / 4 2

Asthma exacerbat ion

4 / M / 3 4

5 / M / 6 3

Asthma exacerbat ion

COPD exacerbation

6 / M / 5 5

7 / M / 4 6

PVC = premature ventricular contraction.

COPD = chronic obstructive pulmonary disease.

Syncope-unexplained, chronic alcohol

use, COPD

Acute bronchospasm and subsequent

p n e u m o n i a

Pregtiancies

Eight women who were pregnant and in the spill area were identified during the surveillance. A

follow-up survey of pregnancy outcomes in October, 1991, found that two of the women who were in the

first trimester of prcgnancy elected to have a therapeutic abortion. Four women who were in the second

trimester of pregnancy at the time of the spill reported symptoms immediately following the spill

including headache, eye irritation, nausea, and rash. All women expressed concern over the possible

effects exposure might have on their developing child. Their physicians have told them their pregnancies

appear to be progressing normally. The remaining two women could not be contacted.

Health Impact of the Spill on Dunsmuir

A total of 498 (70.6%) of the 705 cases listed their city of residence as Dunsmuir. Of these, 391

(78.5%) had home addresses which could be located within or directly adjacent to the Dunsmuir city

Acute Health Effects ofCantara Metani Sodium Spill

2 5


27/37

limits (Figure 4). For the 107 remaining cases, a street address could not be identified or, in a few isolated

cases, the address was much farther south or north of the city limits.

Rates of symptom reporting for cases living within the Dunsmuir city limits are shown in Table

14. A total of 290 cases, or approximately 13.6% of the Dunsmuir city population based on 1990 census

data, sought medical evaluation for symptoms attributed to the spill during the first month after the

incident. Rates of symptom reporting appeared slightly higher among females than males (14.57o vs

12.4%). Larger differences were seen based on age group. Approximately 20% of the 20 to 29 and 30 to 39

age group population reported symptoms while less than 10% of those in the 60 to 69 and over 70 age

groups reported symptoms.

Rates of symptom reporting for each 300 foot zone away from the Sacramento River are shown in

Table 15. Total population included in the analysis (2539) is higher than the Dunsmuir city population

because the analysis includes census blocks adjacent to the Dunsmuir city limits. Overall, 391 (15.4%) of

the Dunsmuir area population rep>orted symptoms based on 1990 census block data. Rates were highest

in the 0-300 foot zone (21.2%), decreased and remained relatively constant at 12-15% for the 301-600, 601-

900 and 901-1200 foot zones, and increased again to 19.8% for the 1201-1500 foot zone. There was no

significant change in distribution when attack rates were stratified by initial symptom onset date (results

not shown). Rates based on age and gender distribution could not be calculated because distribution of

t hese va r i ab l es w i th i n the i nd i v i dua l census b l ocks w as no t ava i l ab l e .


2 6


28/37

Figure 4. Residence Location of Dunsmuir Area Cases *

i I ' a 1

' t / ' U ^ ' J

: / / ///,' A n/

\ ' '7/ / /=// I

" I '( ' vlY \

' V \ \ V\\ ^ J O X I

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I ^ > a

\ \

' ) \ \ r ^ T u J

1 / ' i ' '

' / V > ^ 1 ' '

' / V ^ ^ -i ' ' I

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' ' ; ' '11 ' '' '7

1 i; 1 t,i fS

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\ \ M a \ Y \ \

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[ a l m U l e 5 \ \ \ V ^

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I I ' I

SacramenU Rirer

[almUle 5

Citr Limits

Sovnheni Pacific Railroad

= 5 f-dse

= 7 Cdsa

= 3 Caia

= 9 Case

i n r m m i s M M ^ ^ \ ^ ^ ^

Sovnheni Pacific Railroad A A i J ' ' ' '

100 ?ool latenraJs ."rom Ritct f \ P t j i

T'= y'}t p'< ' :'

/ I 7 a ' ^ 5 n J ^ V ' 1 > '

HIGH SCH00tr/b/ ^ 1/ / / 1

= Kds (SHELTER) rf'? | , i/;fi.' ,[ / / /

= 4 Cases /I ' i 'a*l|a< il ' ^ ^

f ^ i t " i * ^ 1 ' ' ' ^

yc '=* iA*. 1 ', ', ;

\ 1 ^ t a v i r | . J I < .

f I I i I glT ^ I I ' ' '

J D S-Ho'l: ,, 1 ' ' '

f fl / ' I I ' ' '

' .' ' ^ ///S i 7^ -' /

,7/ ///*,i // .''/

r # 1 ^ ' I t i t ' ' f

M l l i l l B m

(=^7 ' ^' //r' I -'''

^J ; ; ; ; ;

' ' / f t

/ / / ' ^ / S / / J f : > t

y / / / ^ / - ' ' / ' ' '

f Z / v / W y y / /

For purposes of presentation, the

northern city limit boundary, which

extends for approximately 2 more

miles, is not shown. No cases

were located in this essential ly

undeveloped, non-residential area.


29/37

Table 14. Dunsmuir City Population and Number (Percent)

Reporting Symptoms by Gender and Age

F e m a l e

D U N S M U I R

p o p u l a t i o n '

1990 census figures.

Only cases in which home located within city limits.

Gender not given for 3 Dunsmuir cases.

Age not given for 15 Dunsmuir cases

Table 15. Dunsmuir Area Population and Number (Percent)

Reporting Symptoms by Distance of Home from

t h e S a c r a m e n t o R i v e r

D U N S M U I R

p o p u l a t i o n '

D U N S M U I R

C A S E S

Distance from River (feet)

3 0 1 - 6 0 0

6 0 1 - 9 0 0

9 0 1 - 1 2 0 0

1 2 0 1 - 1 5 0 0

86 (21.2)

87(13.6)

99 (14.4)

76 (12.9)

43 (19.8)

391 (15.4)

Based on 1990 census block figures, includes areas surrounding city limits (see

Figure 4).



30/37

D I S C U S S I O N

Limitations of This Study

Because this investigation represents only individuals who actively sought medical evaluation, it

is probable that the number of people who exp>erienced health effects from the spill is higher. Those who

experienced milder symptoms may not have associated them with the spill or considered them serious

enough to seek medical evaluation. Others may have left the area temporarily. Tourists and campcrs

may have returned home rather than be evaluated. Several shelter evacuees told us of frustration over

long waits and leaving without being seen at the suddenly overwhelmed emergency room. Anecdotal

reports from residents have indicated that the spill exaggerated preexisting problems in health care access

in the impacted area. However, although some individuals who experienced symptoms were

undoubtedly missed by this investigation, the data presented should provide a reasonable estimate of the

range and severity of symptoms experienced. In addition, because the data represent health effects

reported as they occurred, the study is less likely than subsequent retrospective studies to be affected by

reca l l b ias .

A second major limitation is that we do not know exactly what substances were responsible for

the observed health cffects, although based on known toxicology, MITC is the most likely candidate.

Since reliable air sampling data are not available for the first two days after the spill, we cannot determine

the type and concentration of metam sodium byproducts to which individuals may have been exposed.

Also, there are no current laboratory tests which can specifically identify the presence of these substances

in the body. Therefore, exposure is based on self-report, and dose cannot be classified as to severity.

Because few individuals reported the characteristic horseradish odor of MITC, it would appear

that MITC levels causing symptoms were probably below the MITC odor threshold which has been

reported from one study as 100 ppb. Odor reports suggest that H2S exposure also occurred. Whether

H2S was present in concentrations high enough to produce irritative symptoms is impossible to

determine. However, given that H2S was expected to be present at lower concentrations than MITC,

H2S is a less potent irritant than MITC, and H2S's irritant threshold is almost ten thousand times higher

than its odor threshold, it app>ears reasonable to assume that most symptoms were secondary to MITC

e x p o s u r e .

Major Findings

In this investigation, self-reported exposure to vapors released by metam sodium was most

commonly associated with non-specific neurologic complaints (headache, dizziness) and irritation of the

eye, respiratory tract, gastrointestinal tract, and skin. Although the three sources of information used in

this study represented both self-reported data (questionnaires) and observer-reported data (PIR's and

medical charts), the relative frequency and distribution of symptoms reported were similar regardless of

source. A significantly higher number of symptoms reported by individuals evaluated at the ER may

indicate that this group had the most severe health effects.

Symptoms in nearly all cases were not severe enough to require hospitalization. Of the seven

people hospitalized, four had pre-existing respiratory disease. Exposure effects on pregnant women

remain to be determined. While this study found no cases of spontaneous abortions or birth

abnormalities, the spill may have played a role in two womens' decision to obtain a therapeutic abortion.


2 9


31/37

Because this report includes only symptomatic persons who sought medical care, the actual

symptom rate is probably higher. Even so, the finding that over 15% of Dunsmuir area residents sought

care is quite striking. It was p)0ssible to identify several risk factors. Males and females reported a similar

number of symptoms although the proportion of those reporting symptoms appeared to be slightly

higher for females. Older and very young individuals appeared less likely to report symptoms.

Explanations for the age differences in symptom reporting could include increased tolerance to irritant

effects among older individuals, differences in the degree of exposure among different age groups, or

differences in the ability or willingness to seek care among different age groups.

Our limited geographic analysis suggests a dose-distance relationship. The symptom attack rate

in the 0-300 foot zone was markedly elevated compared to more distant zones. The plateau in attack rates

over the 301-600, 601-900 and 901-1200 foot zones suggest that a clear-cut distance-symptom relationship

might be demonstrated within the 0-300 foot zone. The elevated attack rate in the 1201-1500 foot zone is

inconsistent with our presumed distance-dose symptom relationship. Thus distance from the river of

case homes, as a proxy for exposure, was only somewhat predictive of symptoms. Primary site of

exposure may not correlate well with place of residence, particularly for residences farthest from the

river. Contaminants may have moved in a more complex way than simple dispersal.

Of significance is the finding that symptoms among those rep)orting an odor were nearly identical

to those who did not report an odor. While odor detection data was missing for a high number of cases,

this finding suggests symptoms occurred at chemical concentrations below the odor threshold which

would be consistent with known MITC toxicology. Although detecting an odor could theoretically

indicate a higher level of exposure, this could not be substantiated by the data available.

For the limited number of individuals in whom smoking history was known, smokers tended to

have higher individual symptom rates and a higher number of symptoms overall. This may indicate

smokers were more susceptible to irritant effects of exposure or an unknown interaction exists between

exposure and smoking.

Perhaps the most unexpected finding of the investigation was the occurrence of symptom

reporting days and even weeks after the spill when the possibility of exposure to metam sodium

byproducts was presumed to be minimal. There have been several anecdotal reports of individuals who

left the area after the spill, returned when metam-related chemical levels were not detectable and then

had a recurrence of their symptoms. Others have reported a recurrence of symptoms following

rainstorms two to three months after the spill.

Reasons for the prolonged health effects are unclear. Although initial exposure/symptom onset

information was given for only a little over half of the cases, it appears that most initial exposures and

symptoms occurred within two days after the spill. Symptoms being reported a week or more after the

spill did not appear to differ substantially from those reported initially except that there was a

significantly higher proportion among late symptom reporters of weakness, diarrhea, cough and rash.

There are several possible explanations for the late symptom reports. First, either because of

worry or because of an interest in formally documenting their symptoms for legal purposes, many of the

later medical visits may have represented follow-up visits for initial symptoms which were resolving.

Second, residents may have attributed the development of new health problems which were unrelated to

the spill to the incident. Third, some of the late symptoms could be attributed to psychological trauma,

similar to that seen with post-traumatic stress disorder.^^ Certainly, as a result of the spill, area residents

were subjected to numerous potential stressors such as fear of unknown health effects from exposure,

sudden evacuation from their home, and helplessness in watching the destruction of a once thriving river

which may have been their source of economic livelihood. These stressors could theoretically manifest

themselves as depression, irritability, difficulty concentrating, sleep disturbances and fatigue, etc. Fourth,



32/37

later symptom reports could also represent either slowly resolving or chronic problems related to the

spill. Finally, there could be previously unrecognized or underestimated toxicologic properties of metam

sodium and its byproducts (e.g., persistence in the environment) or sensitization of certain individuals to

these chemicals. Low levels of MITC were reported in vegetation samples taken by the Department of

Fish and Game near Dunsmuir as late as August. Although unlikely, re-exposure to metam sodium

byproducts weeks after the spill cannot be entirely discounted.

C O N C L U S I O N S

The Cantara incident had an undeniably devastating environmental impact on the affected

portion of the Sacramento River. Unfortunately, the full extent of human health effects has not been

determined. The suddenness and resulting chaos of the event made systematic study difficult. The data

in this report is observational, uncontrolled, and subject to several types of biases. Information was

obtained from different sources. Because of the primary need to treat and triage cases, responding

medical personnel could not always obtain or record information for each case in the same manner or to

the same level of completeness.

While the investigation can not conclude causc and effect relationships on a strictly scientific

level, several important points can be made regarding the health effects of the incident. Over 700

individuals sought medical attention for symptoms they believed were related to exposure to the spilled

chemicals--a highly significant finding given the relatively low population of the area. Those who may

have been affected but did not or could not seek medical care were not included in this investigation.

Therefore, it is likely that the number of cases included in this investigation is an underestimate of the

total number of individuals affccted. Symptoms were consistent with exposure to irritant gases.

Irritation of the eyes, gastrointestinal tract, respiratory tract, and skin occurred. Non-specific neurologic

complaints such as headache and dizziness were common. Seven hospitalizations were recorded. No

fatalities or adverse pregnancy outcomes were observed. Gender, age, and smoking status were factors

which appeared to affect symptom reporting.

Some symptoms probably occurred at chemical concentrations below odor thresholds. In the

Dunsmuir area, exposures appeared to occur on either side of the river at distances of up to a quarter-

mile from the river. The exact types and concentrations of substances which were present is not known.

Because there were no fatalities and few hospitalizations, it is unlikely that high-level exposures occurred.

Most exposure and symptom onsets appeared to occur within the first two days after the spill.

However, symptoms were unexpectedly reported many days and weeks after the spill. Reasons are

unknown. Long-term health effects of exposure, including effects on the reproductive system, are

u n k n o w n .

R E C O M M E N D A T I O N S

Genera l Recom m enda t i ons

The public health implications of this incident are far reaching. However, it is beyond the scope

of this report to make specific recommendations within the entire arena of affected institutions and

agencies. Major concerns raised by the incident are addressed below.

H A Z A R D O U S M A T E R I A L C L A S S I F I C A T I O N A N D T R A N S P O R T A T I O N

Although metam sodium is a biocide, which by definition is a threat to the environment if used

incorrectly, it was not classified as a hazardous material by the US DOT. As a result, the herbicide was


31


33/37

shipp)ed in a standard non-puncture resistant tank car which neither was placarded nor carried specific

toxicologic information and recommendations regarding accidental release. Whether a different type of

rail car would have prevented the spill is unknown. However, procedures for

california dept. of health services study

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