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ENVIRONMENTAL AND OCCUPATIONAL EXPOSURE TO INORGANIC ARSENIC

Marie Vahter Na t iona l I n s t i t u t e o f Environmental Medicine, Stockholm, Sweden Key words: a rsen ic - metabo l i t es - u r i n e

The u r i n a r y concent ra t ion o f a rsen ic may be a u s e f u l i n d i c a t o r o f t h e exposure

t o i no rgan ic a rsen ic s ince the main rou te o f e x c r e t i o n i s v i a t h e kidneys.

However, i t i s necessary t o use an a n a l y t i c a l method, which measures t h e meta-

b o l i t e s o f inorgan ic a rsen ic ( i no rgan ic A s I I I and AsV, methy la rson ic a c i d (MMA)

and d ime thy la rs in i c a c i d (DMA)) only, and no t o rgan ic a rsen ic compounds L ike

arsenobetaine, which may be present i n h igh concent ra t ions i n c e r t a i n f i s h and

crustacea and which are excre ted r a t h e r r a p i d l y i n t h e u r i n e (Vahter e t al,

1983; Marafante e t at, 1984). I n the present study we have determined t h e

concent ra t ions o f me tabo l i t es o f inorgan ic a rsen ic (iAs-met) i n u r i n e o f 99

sub jec ts w i thout known exposure t o a rsen ic (randomly se lec ted from the popula-

t i o n i n two Swedish c i t i e s , Stockholm and Vasteras), and i n u r i n e o f 20 mate

workers exposed t o a rsen ic t r i o x i d e a t a non-ferrous smelter i n n o r t h e r n Sweden.

A l l u r i n e samples were deepfrozen u n t i l ana lys is . The sum o f me tabo l i t es o f

inorgan ic a rsen ic i n u r i n e were determined by a rs ine genera t ion (Perk in Elmer

MHS-20, a d d i t i o n o f sodium borohydr ide t o a c i d i f i e d u r i n e samples) / atomic

absorp t ion (Perk in Elmer 303, equipped w i t h EDL-Lamp and deuter ium background

c o r r e c t i o n system) (Nor in and Vahter, 1981). Peak areas were used f o r quant i -

t a t i o n . For q u a l i t y c o n t r o l purposes 3 human u r i n e samples sp iked w i t h a m ix tu re

o f arsenate, MMA and DMA (19:25:56) were analyzed a t t h e beg inn ing an end o f

each run. Separat ion o f t he i no rgan ic arsenic, MMA and DMA i n t h e u r i n e was

c a r r i e d out on i o n exchange columns o f AG 50W X8 (13 x 1 cm, B i o Rad, USA) (Tam

e t a t 1978; Foa e t aL, 1984). Arsenic i n the f r a c t i o n s was determined by a r s i n e

generation1AAS. Recovery o f arsenate, MMA and DMA, added t o human u r i n e was 106

f 8.0%.

The concent ra t ions of a rsen ic me tabo l i t es i n the u r i n e were skewely d i s t r i b u t e d

(Figures 1 and 2 ) . Among the unexposed sub jec ts most values centered around 8.2

1J.g Aslg c rea t in ine , t he o v e r a l l geometric mean, wh i te fou r u r i n e samples con-

ta ined more than M pg Aslg c rea t in ine , the h ighes t be ing 52 pg Aslg c r e a t i n i n e

(Figure 1). The geometric mean values were very s i m i l a r t o the median values,

whi te the a r i t h m e t i c means were about 30% higher, due t o the skewed d i s t r i b u -

t i o n . S i m i t a r u r i n a r y concent ra t ions o f iAs-met have been repo r ted from F in land

(Valkonen e t at, 19831, FRG (Apel and Stoeppler, 1983) and I t a l y (Foa e t at,

19841, and s l i g h t l y h igher from Belgium (Buchet e t at, 1980). With the assump-

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t i o n t h a t the d a i l y u r i n a r y e x c r e t i o n i s about 60% o f t h e dose (Buchet e t at,

1981), i t can be est imated t h a t the d a i l y i n t a k e o f i no rgan ic a rsen ic among t h e

general popu la t i on i s about 15-25 pg As i n most European count r ies .

U r ina ry concent ra t ion o f iAs-met were found t o be independent o f sex, p lace of

residence, smoking h a b i t s and consumption o f beer and wine. Sub jec ts who o f t e n

a te f l a t f i s h and crustacea had about 1.5 t imes h igher u r i n a r y concen t ra t i on o f

iAs-met than sub jec ts who a t e t h i s k i n d o f seafood less o f t e n (p<O.OI), o r

sub jec ts who a t e o ther k inds o f sea f i sh o r f reshwater f i s h . Th is would f i t w i t h

f i n d i n g s t h a t 2-10% o f the t o t a l a rsen ic may be i n form o f i no rgan ic a rsen ic

(Lunde, 1977; Brooke and Evans, 1981). However, separa t ion o f t he d i f f e r e n t

u r i n a r y me tabo l i t es showed t h a t DMA was the o n l y me tabo l i t e which c o r r e l a t e d

w i t h the t o t a l me tabo l i t e concen t ra t i on ( c o e f f i c i e n t o f c o r r e l a t i o n 0.996, compared t o 0.70 f o r i no rgan ic a rsen ic and 0.50 f o r MMA), i n d i c a t i n g t h a t t h i s

me tabo l i t e accounted f o r most o f the v a r i a t i o n o f iAs-met. When subd iv id ing t h e

sub jec ts w i t h respect t o degree o f exposure, i t was found t h a t t h e concen t ra t i on

o f i no rgan ic a rsen ic and MMA were r a t h e r constant independent o f t he degree o f

exposure, wh i te sub jec ts w i t h more than 10 pg iAs-met/g c r e a t i n i n e had more

than 6 t imes h igher u r i n a r y concent ra t ion o f DMA than those w i t h Less than 10 pg

iAs-met/g c r e a t i n i n e (Table 1). Subd iv id ing the sub jec ts according t o exposure

t o f i s h arsenic, i.e. t he concent ra t ion o f o rgan ic a rsen ic compounds ( t o t a l

a rsen ic minus iAs-met) i n the urine, showed t h a t u r i n a r y i no rgan ic a rsen ic and

MMA were independent o f t he degree o f exposure, w h i l e sub jec ts w i t h

Table 1. Concentrat ions o f inorgAs, MMA and DMA (pg As/g c r e a t i n i n e ) i n r e l a t i o n t o the concent ra t ion o f t o t a l iAsmet o r orgAs.

(10 pg iAs- >I0 1-19 iAs- (20 pg org- >20 pg org- met/g c rea t . met/g c rea t . As/g c rea t . As/g creat.

~ ~~~~~~~~~

N 8 5 6 7

i norgAs 1.0 i 0.41 1.6 f 0.93 1.1 i 0.43 1.4 f 0.90

MMA 0.8 i 0.37 1.4 i 1.4 0.9 i 0 . 4 3 1.2 f 1.2

DMA 4.0 f 1.4 24.8 i 10.2 3.6 f 0.86 19.2 f 12.8

more than 20 pg orgAs/g c r e a t i n i n e had more than 5 t imes h igher concent ra t ions

o f DMA i n the u r i n e than those w i t h tower u r i n a r y concent ra t ions o f orgAs. Th is

would suggest t h a t people a re exposed t o DMA from f l a t f i s h and crustacea r a t h e r

than t o i no rgan ic arsenic. However, i t may be a ques t i on o f exposure t o t r i -

methy la rs ine ox ide (TMO) a lso. TMO has been de tec ted i n f ish, e s p e c i a l l y a f t e r

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4-

3-

2-

storage f o r some t ime i n freezer, probably as a consequence o f degradat ion o f

arsenobetaine (Nor in e t at, 1985). With t h e a n a l y t i c a l method used TMO w i l l

co-chromatograph w i t h DMA. We are now under way t o i n v e s t i g a t e whether o r no t

TMO i s present i n t h e ur ine .

- - -

1-- -

number of subjects

40 f

10 20 30 40 50 60 ug As/g creatinine

Figure 1. Concentrat ions o f iAs-met i n u r i n e o f t he genera l popu la t ion .

I n the study on occupa t iona l l y exposed sub jec ts the f i r s t - v o i d morning u r i n e was

c o l l e c t e d f o r seve ra l days d u r i n g the working week. The u r i n a r y concent ra t ions

of iAs-met increased du r ing the f i r s t day of exposure, whereaf te r t hey l e v e l l e d

o f f , i n d i c a t i n g a steady s t a t e between exposure .and excre t ion . The m a j o r i t y o f

t he samples contained Less than 200 pg As/g c rea t in ine , but 2 samples had over

300 pg As/g c rea t in ine , t he h ighes t 328 pg As/g c r e a t i n i n e (F igure 2). Separa-

t i o n o f u r i n a r y me tabo l i t es showed t h a t du r ing the steady state, i.e. a f t e r t h e

f i r s t day o f t he working week, on average 19% o f the u r i n a r y As-met was i o r g a n i c

arsenic, 20% MMA and 61% was DMA, which i s very s i m i l a r t o the d i s t r i b u t i o n o f

u r i n a r y metabo l i tes among the genera l popu la t i on (non-f ish ea ters ) w i t h con-

s i d e r a b l y Lower exposure (Table 2). Thus t h e me thy la t i on does no t seem t o be

sa tura ted even a t t he exposure l e v e l s found among the smelter workers. A f t e r t w o

days f ree from work as much as 80% o f t he u r i n a r y a rsen ic me tabo l i t es was i n

form o f DMA, which i s i n agreement w i t h exper imental s tud ies showing t h a t

inorgan ic a rsen ic i s excre ted main ly the f i r s t day a f t e r exposure, whereafter

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DMA i s t he major u r i n a r y me tabo l i t e (Vahter and Marafante, 1983). A L L t h ree

me tabo l i t es showed a s i g n i f i c a n t c o r r e l a t i o n (r 0.94-0.991 w i t h t h e t o t a l

u r i n a r y metaboli tes, which proves t h a t exposure t o i no rgan ic a rsen ic w i l l r e s u l t

i n an increased e x c r e t i o n o f i no rgan ic a rsen ic i n t h e ur ine .

Table 2. Ur ina ry metabol ies o f i no rgan ic a rsen ic

Conc. % o f t o t . u r i n a r y iAs-met range ........................................

Popu la t i on N 1-19 As/g creat. inorgAs MMA DMA

General pop. non- f i sh ea ters 6 4-8 18 f 4.3 16 i 4.7 65 f. 4.6

Smelter workers ongoing exposure 9 15-300 19 f. 3.2 20 f. 4.2 61 f. 6.3

Smelter workers a f t e r weekend 6 12-140 9 f 2.7 13 i 3.6 78 i 4.3

REFERENCES

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Brooke, P.J. & W.H. Evans: Determinat ion o f t o t a l i no rgan ic a rsen ic i n f i sh , s h e l l f i s h and f i s h products. Analyst . 1981, 106, 514-520.

Buchet, J.P., Lauwerys, R. & H. Roels: Comparison o f severa l methods f o r t he de te rm ina t in o f a rsen ic compounds i n water and i n u r ine . I n t Arch. Occup. Environ. Health, 1980, 46, 11-29.

Buchet, J.P., Lauwerys, R. & H. Roels: U r ina ry e x c r e t i o n o f i no rgan ic a rsen ic and i t s me tabo l i t es a f t e r repeated i n g e s t i o n o f sodium metaarsen i te by volunteers. In t . Arch. Occup. Environ. Health, 1981, 48, 111-118.

FoA, V., Columbi, A. & M. Maroni: The s p e c i a t i o n o f t he forms o f a rsen ic i n t h e b i o l o g i c a l mon i to r i ng o f exposure t o inorgan ic arsenic. S c i . To ta l . Environ. 1984, 34, 241-259.

Lunde, G: Occurrence and t rans fo rma t ion o f a rsen ic i n the marine environment. Environ. Hea l th Perspect. 1977, 19, 47-52.

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Tam, G.K.H., Charbonneau, S.M., Bryce, F. 8 G. Lacro ix : Separat ion o f a rsen ic me tabo l i t es i n dog plasma and u r i n e f o l l o w i n g i n t raveous i n j e c t i o n o f 74As. Anal. Biochem. 1978, 86, 505-511.

Vahter, M., Marafante, E. & L. Dencker: Metabolism o f arsenobetaine i n mice, r a t s and rabb i t s . S c i . T o t a l Environ. 1983, 197-211.

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