Lake Almanor Cloud Seeding Project

Recent Challenges

Presented to

Weather Modification Association

April 25-27, 2012

Las Vegas, Nevada

Byron L. Marler 1, Edward F McCarthy2 and Ken Ericsson3

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Challenges

• Concerns of a small, vocal group of citizens

• Plumas County Board of Supervisors (BOS)

• Almanor Basin Watershed Advisory Committee

(ABWAC)

• Community forum involved stakeholders

– concerned citizens

– interested citizens

– PG&E representatives

– Scientists

– public agencies

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Concerned Citizen Perceptions – Cloud Seeding

• Chemicals = health and environmental hazards

• Non-technical interpretation of various internet

sources and personal opinions

• MSDS

• Chem-trails

• Claims of cancer clusters “in my neighborhood ---”

• Is it safe for children to play in our yards?

• We moved here for a safe, clean environment.

• And some science based questioning -- what about

nano-silver particles?

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ABWAC FORWARDS QUESTIONS - EXAMPLES

• Chemical species released to atmosphere?

• Amount of each chemical released in operation?

• Physical and aerodynamic properties of seeds?

• Fate of seeding chemicals in air, soil and water?

• Why is the toxicity of silver iodide described differently

by MSDS sheets and by PG&E?

• Regarding Silver Iodide in Nano Form:

– Is it toxic? Status of research? Can it be inhaled?

• Provide test data (not summaries) from all studies.

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PG&E RESPONSE

• Geochemistry and Impacts of Silver Iodide Use in Cloud

Seeding. Cardno ENTRIX report provided at ABWAC

Meeting, May 25, 2011, Chester, CA

• Responses to Questions Regarding Cloud Seeding in the

Lake Almanor Basin Updated: September 13, 2011

• Narrative vs Q/A format – specific Q/A achieved

– Lake Almanor Cloud Seeding Project

– Environmental Effects

– Air Quality

– Regulatory Setting

– Nano-particles

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Lake Almanor -- Mount Lassen

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Lake Almanor Cloud Seeding – operating since 1953

– Target area –

500 sq miles

above Lake

Almanor

– 10 ground-

based radio-

controlled

seeding

generators

– No aircraft

seeding

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Lake Almanor Cloud Seeding – “Silver Iodide”

• 21.5 grams/hour/seeder

• Seeding solution is 98%

acetone.

• Each seeding particle

• 64%, 10%, 1%, 25%

• AgI 0.8 AgCl 0.2 0.005 Bi2O3 KCl = seeding salt ~ silver iodide.

• PG&E Cloud Seeding Summary 1999 – 2011

• 212 days Nov – May; 16-49 days/season; 20-93 kg; and 3 suspended seasons

• All acetone oxidized to carbon oxides, nitrogen oxides

and water vapor.

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Environmental Effects

• Similarity in nomenclature between silver iodide and

free silver ion leads to lay-person concerns.

• Important to understand that silver iodide is used in

cloud seeding, not silver ions.

• PG&E Consultants - Cardno ENTRIX (CE) 2011

report summarized the evidence-based studies

related to cloud seeding and public health

correlations:

– no correlation between cloud seeding and public health

– Measured concentrations are typically many times safer than

the drinking water standard.

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Environmental Effects

PG&E Response – CE 2011 Report

• Most studies of silver in the environment have

measured total silver, not the concentrations of the

individual silver species.

• Since the free silver ion is the toxic form of silver,

these studies overestimate the actual toxicity of silver

iodide, which is practically insoluble

• Seeding concentrations pose no adverse

environmental impacts

• Key References:

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Air Quality Question – Winter Inversions

• Would cloud seeding

agents concentrate near

the ground surface

creating health

problems for those living

under these inversion

layers?

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EPA’s AirNow website – Air Quality Index (AQI)

• AQI Categories

• Area AQI based on 8-hour

maximum ozone value Lassen

Monitoring Site and 24-hour

average PM2.5 value from the

Chester

• Based on AQI values PG&E’s

cloud seeding operations occur

during dates of satisfactory

(Good) or acceptable (Moderate)

air quality index values

Good Moderate

Unhealthy for

Sensitive

Groups

Unhealthy Very

Unhealthy Hazardous

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Air Quality

• Cloud seeding operations are

done during windy, stormy

condition, not typically associated

with inversions.

• Cloud seeding aerosols released

during these conditions would not

concentrate near the ground nor

create health problems for the

Plumas County residents.

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Air Quality - NSAQMD Agency Review

• NSAQMD calculated the emissions and

compared the results to the criteria for an

air permit, confirmed no permits required.

• p-dichlorobenzene was the only chemical of any

concern and NSAQMD determined the potential

emission rate of p-dichlorobenzene is 30 times lower

than trigger for a permit.

• p-dichlorobenzene is not released to the air but is

consumed by combustion, so NSAQMD’s analysis is

hypothetical

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Materials Safety Data Sheets for Worker Safety

• MSDS are prepared by the manufacturer and lists

hazards due to ingestion, skin contact, and inhalation.

– MSDS covers the range of exposures and hazards that may

occur from manufacture to end use.

– The hazards identified are ones that could occur to workers

handling the bulk material

– The hazards identified in the MSDS do not apply to cloud

seeding related environmental levels of exposure because of

the resulting very small chemical concentrations

– MSDS cites a study on rats that required a very high intake of

silver iodide for the hazard; the cited level is the equivalent of

feeding the animal one-fourth its body weight in silver iodide.

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Toxicity and Hazards

• Dose-Response

– All chemicals, including water, can

be toxic to humans; toxicity is determined by the dosage

(the amount of chemical applied to plant or animal).

• Important - Putting Risks/Hazards in Perspective

– The cloud seeding chemicals are shown in the MSDS as

non-carcinogenic but do potentially produce toxic effects

depending on dosage.

– How do seeding chemicals compare to other commonly used

chemicals like table salt or tooth paste in terms of relative

hazard?

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Putting Risks/Harzards into Perspective

• National Fire Protection Association (NFPA), Hazardous

Materials Identification System (HMIS) safety ratings and lethal

dose level to 50% of test animals (LD50) are summarized in

Table A

• The MSDS for sodium fluoride indicates its potential toxic

hazards are more severe than the seeding chemicals; however,

sodium fluoride is used in very low concentrations (dosage) in

toothpaste, resulting in a non-toxic response.

• Environmental concentrations of the seeding chemicals are

extremely small (parts per trillion range) and for practical

purposes can be considered non-toxic, for the same reason as

for sodium fluoride in toothpaste (dose-response relationship).

Use Chemical Chemistry NFPA / HMIS Ratings* Lowest

LD50 **

Health Fire Reactivity (mg/kg)** Internet web link to MSDS

Cloud seeding

particles

Silver Iodide AgI 2 0 0 2820 r http://www.sciencelab.com/msds.php?

msdsId=9927257

Silver Chloride AgCl 2 0 0 5000 g http://www.sciencelab.com/msds.php?

msdsId=9927255

Bismuth Oxide Bi2O3 1/2 0 0 Not

Available

http://www.sciencelab.com/msds.php?

msdsId=9927457

Potassium Chloride

KCl 1 0 0 1500 m http://www.sciencelab.com/msds.php?

msdsId=9927402

Cloud seeding fuel

& solution –

consumed in flame

- not emitted as

this chemical to air

Acetone C3H6O 1/2 3 0 5340 m http://www.sciencelab.com/msds.php?

msdsId=9927062

p-dichlorobenze

C6H4Cl2 2 2 0 500 r http://www.sciencelab.com/msds.php?

msdsId=9923722

Propane C3H8 1/0 4 0 Asphyxiant www.amerigas.com/pdfs/safe_eng.pdf

Table salt Sodium Chloride

NaCl 1 0 0 4000 r http://www.sciencelab.com/msds.php?

msdsId=9927593

Toothpaste

ingredient

Sodium Fluoride

NaF 3/2 0 0 52 r http://www.sciencelab.com/msds.php?

msdsId=9927595

Food ingredient Caffine C8H10N4O2 2 1 0 127 m http://www.sciencelab.com/msds.php?

msdsId=9927475

Medicine Asprin C9H8O4 2 1 0 200 r http://www.sciencelab.com/msds.php?

msdsId=9922977

Food ingredient Vitamin D3 C27H44O 3 1 0 42 r http://www.sciencelab.com/msds.php?

msdsId=9923455

* NFPA ratings are shown; / HMIS shown if different from NFPA; number hazard ratings; larger numbers indicate greater hazard

** Toxin weight / kilogram of body weight; test animal rat - r, mouse- m, guinea pig – g; smaller numbers imply greater toxicity

All chemicals produce hazards at high concentrations (dosages); for example, all chemicals in this table can produce tissue

(skin, eyes, respiratory, etc.) irritation.

TABLE A - MSDS Summary

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Nanoparticles – Particle dimension less than 100

nanometers

• 100 nanometers = 0.1 micron

• Cloud seeding particles (0.05 – 0.1 micron) are nano

• USEPA is evaluating the toxicity of nanosilver as

applied in consumer goods

– clothing, medical equipment, shampoo, toothpaste,

nutritional supplements, ---

– focus of EPA review - use of the antimicrobial form

of silver (silver ion) as nanoparticles

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Nanoparticles

• Engineered nanosilver - specifically made to be

predominantly the ionic form of silver, which is the

effective anti-microbial agent.

• Cloud seeding particles are not engineered nanosilver.

• Nanoparticles produced by cloud seeding are silver

iodide particles, which do not have the anti-microbial

effects of engineered ionic silver nanoparticles.

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Nanoparticle Regulation

• Air quality regulations for particulate matter -

10 micron (fine) and 2.5 micron (fine) size.

• Nanoparticles (ultrafine) fall within both categories.

• The emission amount from cloud seeding is far less

than the triggers for permits controlling emissions of

fine particles.

• Engineered nanoparticles, are being considered for

regulation by the USEPA.

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USEPA Recommends Further Research

• Effects of engineered silver nanoparticles on humans

• Uncertainty is that engineered nanoparticles of

elemental or ionic silver can penetrate cell walls,

whereas the larger elemental or ionic silver does not.

• The USEPA (2010 a) notes that silver iodide is used

for cloud seeding, but the recommended studies do

not extend to the combustion-related formation of

nano-sized particles of silver iodide.

• Silver iodide retains its composition – negligible

ionization in environment.

• Research summarized in Cardno ENTRIX, 2011

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OUTCOME – ABWAC Reports

• “There’s no evidence that cloud seeding has

negative effects on the environment or public health.

But more research should be done.”

• Recommends

• Assure cloud seeding installations located in Plumas County are secure,

including all chemicals stored on site.

• Inform the county of any proposed changes to current cloud seeding programs.

• Work with PG&E science staff and outside experts in the fields of ecotoxicology,

atmospheric chemistry and nano-technology to develop a rigorous monitoring

program.

• Include silver as a monitored constituent as part of the long-term water quality

monitoring of Lake Almanor.

• Use a website to provide real-time notice of when cloud seeding activities are

occurring, as well as cloud seeding activities to date.