### Biologic a l Report 85(1.10) Contaminant Hazard Reviews April 1987 Report No. 10



## MERCURY HAZARDS TO FISH, WILD LIFE, AND INVERTEBRATES: A SYNO PTIC REVIEW

by Ronald Eis l er

U. S. Fish and Wildlif e Service Patuxent Wildlife Research Center Laurel, MD 20708SUMMARY

Available literature on the ecol ogi cal an d toxicologi ca l aspe cts of mercury (Hg ) in the environ ment, with spe c ial refere nce to fish a n d wildlife re so urces, i s revi ewe d and su mmari zed. Subdivisi ons in clud e so urce s, chemi c al p r o pertie s , backgrou nd con c e n tration s , acu t e and ch roni c toxicity, sub l ethal effects, and pro p o s e d crite r ia to prot ect se nsitive reso urce s.
Mercury ha s been u s e d by man for at least 2,300 yea r s, mo st re ce ntly as a fung icide in a g ri cu lture, in the manufa c ture of chlori ne an d sodi um hyd r oxide, as a slim e cont rol a gent in the pu lp and pa per i ndu stry, in the prod uctio n of plasti cs a nd e l ectri c al ap pa ratus, a nd in mining an d smelting ope ra tions. Mercu ry burden s in

some e n viro n m ental co mp artment s are estimated to have in crea sed up to 5X p r ecultura l levels, prim arily as a result of man' s activities. T he co nstructi on of artificial rese rvoirs, fo r example, which relea s e s Hg from floo ded soil s, has con t ributed to the obse rved ele v ation of Hg c oncentrations in fis h tis s ues from thes e loc a lities

. Elevated levels of Hg in living org ani sm s in Hg-conta m inated a r ea s may persi st for as long a s 100 yea r s a fter the sou r ce of pollution ha s been di sconti nued. One m ajor con s eq u ence of incre a se d mercu r y use, co uple d with carele ss wa ste disp osal practices, ha s b een a sharp increa se in th e num be r of epidemi c s of fatal mercury poisoning s in human s, wildl i fe, and aquat ic org ani sm s.

Most autho riti es ag ree o n six points: (1) mercury an d its com poun d s have no kn own bi ologi ca l function, an d the pre s en ce of the metal in the cell s of living orga nism s is u nde sirable an d pote n tially haza r d ous; (2 ) form s of

merc ury with relatively low toxic i ty c an be trans f o rmed in to forms of very high toxic i ty, s u c h as methylmercury, throug h biolo g ical a nd oth e r processe s; (3) me rcury can b e bio c o n ce ntrated in orga nisms a n d biomag nifie d throug h food chai ns; (4 ) m e rcury is a m u tagen, terat ogen, an d ca rcino gen, an d cau s e s emb ryocidal, cytoch emical, and histo pat hologi cal effe cts; (5 ) so me spe c ie s of fish and wil d life contai n high con c e n tration s of Hg that are n o t attributable to human act i vities; (6) ant hrop oge nic u s e of Hg sho u ld be curtail ed, as the differen c e bet wee n tolera bl e natural b a ckgroun d level s of Hg an d h a rmful effect s in the enviro n ment is exceptio nally small.

Con c e n tratio ns of total Hg lethal to sen s itive, r epresentative, non human spe c i e s ra nge fro m 0.1 to 2.0 ug/l (ppb ) of medi um for aqu atic org ani sm s; from 2,200 to 31,000 ug/ kg body weig ht (acute oral) a nd 4,000 to 40,000 u g /kg (dieta ry) for b i rds; an d from 100 to 500 u g /k g bo dy wei ght (daily do se) and 1,0 00 to 5,000 ug/kg diet for mam m als. Org a n o mercu r y co mpoun ds, e s peci a lly methylmercury, are alway s more toxic than inorg ani c Hg compo u n d s. Num e ro u s biolo g ical and abioti c factors mo dify the toxicity of Hg comp oun ds--sometim e s by an orde r of mag n itude or m o re--but the me cha n ism s of acti on a r e notclear. Signifi cant adve r se subl ethal effe cts were ob se rve d among sele cted aq uatic spe c ie s at wa ter con c e n trat ions of 0.03 t o 0.1 ug Hg/l. For som e bi rds, adverse effects--pre domi n antly on rep r o ductio n --have been a s soci ated with tota l Hg co ncentrations (i n ug/ kg fresh weig ht) of 5,000 in feather, 900 in egg, and 5 0 to 100 in diet; and with d a ily intake s of 64 0 ug/kg b ody weig ht. Sensitive nonhum an mammal s sho w e d sig n ificant adve r se effects of Hg when d a ily intake s we re 2 50 ug/kg b ody weight, whe n d i etary levels were 1,100 u g /k g, or when tissue con c e n tration s exceede d 1,100 ug/kg.

The mo st re cent mercury criteria p r op osed by the U. S. Environmen tal Protection Agency for p r otection of fresh w ate raq uatic life are 0.012 ug/l me dium (4 -day a v erage ), not to excee d 2.4 ug/l on an ho urly avera ge; however, the s e criteri a offer only limite d prote c tion to fr esh w ate r eco s ystem s . The salt wate r criteri a of 0.025 ug Hg/l mediu m (4-day avera ge), not to excee d 2.1 ug/l hourly , are un satisfa c to ry for the protecti on of marin e life. For the p r ote c tion of se nsit ive spe c ie s of mammals a n d bird s that re gularly con s u m e fish and o t her aqu atic orga nisms, to tal Hg co ncen trations in the s e prey item s shoul d pro b a b ly not excee d 100 ug/ kg fresh weig ht for bird s, and 1,1 00 ug/kg for small mammal s . The sig n ifican ce of elev ated Hg level s in tissue s of fish and wil d l i fe is not fully understood; so me spe c ie s o f marine pin n i ped s, for example, norm a ll y contain hig h con c e n trati ons of Hg in vario u s tissu es witho u t apparent a d verse effect s. Usu a lly, howeve r , con c entration s in exce ss of 1,1 00 ug/kg fresh weight of tissu e (liver, kid n e y , blood, brai n, hair) sho u l d be co nsi dered as p r e s um ptive evidence of an enviro n me ntal mercury probl em.



### 2Four cou r ses of action no w seem warran ted. First, to xic mercu r ial s in agri c ultu re and ind u stry sho u ld be repla c e d by less toxic su b s titutes. Second, co ntrol s sho u ld be a p p lied at the p o int of origin to prevent the discha rge of potentially ha rmful Hg wa stes. Third, co nt inued p e rio d ic monito rin g of Hg in fish and wildlife i s need ed for id entification ofpotential pro b lem area s ., and for evalu a tion of ongoi ng mercu r y curtailme n t prog ram s . And fourth, ad ditional re se a r ch i s me rited on mech ani sms of mercu ry accu mulatio n and detoxi c ation in comp aratively pristine e c osyste ms.

DISCLAIMER
Mention of tra de name s o rcomm ercial p r odu cts d o e s not con s titute U.S. Govern ment endo rse m ent or

recomme ndat ion for use.

This repo rt sh ould be cited as follo ws:
Eisler, R. 19 87. Mercury hazard s to fish, wildlife, an d inverteb rate s: a synopti c review. U.S. Fish and Wildlife Servi c e Biologi cal Rep o rt 85 (1.1 0).



### 3SUMMARY DISCLAIMER ACKNOWLE DGME NTS INTRODUCT I ON SOURCES OF ENVIRO NMEN TAL MER CUR Y CHEMI CAL PROPERTIES MERCURY IN MINAMATA, J APAN BACKGR O U ND CO NCE N T RATIO N S GENERAL NO NBIOLO G I CAL BIOLOGICAL ACUTE AN D CH RO NIC T O XICITY GENERAL AQUATIC O R GANISMS BIRDS MAMMALS OTHE R GR O U PS SUBLETHAL EFFECTS GENERAL AQUATIC O R GANISMS BIRDS MAMMALS OTHE R GR O U PS CU R R ENT R E COMME ND ATIONS LITERATU R E CITED TABLES Numb er 1 Industri a l and other u s es ofmercury in th e Unit ed States in 19 59 an d in 1969. All values are in metric ton s (modified from Montague a n d Montagu e 1 971) 2 Amount of mercury in som e global reservoirs (NAS 1 978), an d re si den ce times (Clarkson et al

. 1984 ) 3 Some pro p e r ties of mercu ry and its com poun ds 4 Mercury con c entration s in sele cted bi olo g ical a nd no n b iologi cal mat e rial s coll ecte d from Minam ata Bay, Japan, a nd enviro n s. Con c e n tratio ns are in mg Hg/kg (pp m ) f r esh wei ght (FW), o rdry weight (D W) 5 Mercury con c entration s in water a nd se diments 6 Mercury con c entration s in field coll ection s of sele cted spe c ie s of flora and fau na. Values sh o w n are in mg Hg/kg fresh wei ght (FW), o rdry weight (DW) 7 Toxicities of i norg ani c and orga nic m e rcury com pou n d s to sel e cte d spe c ie s of aquati c org a n i sms 8 Toxicity to birds of mercu r yadministe re d by oral, dietary, or other ro utes 9 Toxicity of organom ercu ry comp oun ds t o sele cted m a mmalia n sp ecie s 10 Sublethal effe cts of organo mercury com poun ds a d mi nistered to se lected spe c ie s of mammal s 11 Propo se d me rcu r y criteria f o r protecti o n of various re source s and h u man he alth

FIGURES Numb er 1 Major tra n sfo r mation s of m e rcury in the envir on ment (modified from Beijer and Je rnelov 19 79 ) 2 Mercury con c entration s in l i vers of four s peci e s of pin n iped ma mm als (from Eisl er 198 4)

AC K N O W LE DGME NTS I thank J. Hig g is an d I. Moore for se cret arial hel p; L. J. Garrett and J.E. Habe r for literature ret r ieval; W.N. Beyer, T.A. Haine s , M.C. Perry, J.G. Wie ner, and M. R. Winfrey for reviewin g the manu script; a nd P.H. Esch meyer a nd J.R. Zu bo y for editorial servi c e s

.



### 4INTRODUCT I ON
The elem ent mercury (Hg ) and its comp ound s have n o kno w n n o rmal metaboli c functio n . Their p r e s en ce in the cell s of living org ani sm s rep r e s e n ts contami nat io n from natu r a l and anthrop ogeni c sources; all su ch contami natio n must be reg a rde d as u n d e si rable a nd potentially ha zardou s (NA S 1978).

The mo st imp o rtant ore of mercury, cin n abar (me r curi c sulfid e), ha s bee n mined continu o u s ly sin c e 41 5 BC (Cla rkson an d Marsh 19 82 ). In the period before the industri a l rev o lution, Hg was u s ed exte nsively in gol d extraction a n d in the manu facture of felt hats an d mirrors; in the 18 00's, it wa s u s ed in the chl o ral k ali ind u st ry, in the manufa c ture of ele c tri c al instru ment s, and a s a m edical antisep tic; and sin c e 1900, it has b een u s ed in pharma ceuti c als, in agri c ult u ral fungi cid e s , in the pulp and pa per in d u stry a s a sli m icide, an d in the prod ucti on of plasti cs (Cla rkson an d Marsh 19 82). Cu rre nt worl d use of mercury i s estim a ted a t 10,000 to 15 ,000 metri c tons

annu ally (Bou dou an d Rib e y re 1983 ), of whi c h the Uni t ed States accou n ts for ab out 18% (Cl a rkson an d Marsh 1982 ).

The first case s of fatal mercury poi so nin g were re por t ed for two me n in a Europ e an ch emical laboratory in 1865 (Da s et al. 1982). Th e first do cum ented hum an poisoni ng fro m an agri c ult u ral expo su re to methylmercury

occurre d in 1 940 (Da s et al. 1982). As summari ze d b yElhassa ni (1983 ), exposure of hum an s to mercu r y comp oun ds may result fro m dermal a p p lication (e.g ., 1,600 infant s in Argentin a showed sympt o ms of Hg poisoning aft e r a laun dry treated thei r di apers with a Hg di sinfe c ta nt), from diet (i.e., ingestio n of Hgcontami nated fish, pork, se afood s, or grains), and fro m conta c t by re spiratory ro utes (e. g ., occup a tional exposure of mercury fungi cide a ppli c ato r s in Ni ca r a g ua). Spora d i c inci den ce s of human poi soni ng s have

occurre d in the United States, the Soviet Union, an d Canad a; and m ajor epi demi c s have be en reporte d in Jap an, Paki stan, Guatemal a, Ghana, Yu gosl a via, and Iraq (Cl a rkso n and Ma rsh 1982; Das et al. 1982; Elhassani 1 9 83; Gre ene r and Kochen 1983 ). In 1972, for ex amp l e, there we re 6,530 ho spit al admissio n s within 18 month s (4 59 ho spital d eaths) amo n g Iraqi farme r s who ate brea d made from see d wh eat treated with a methylmercu ry fungicide. A water solub l e red dye wa s wa sh ed off the whe a t, with the assump tion that the mercury woul d be equ ally solu ble. Before the wh eat wa s co nsume d by human s, it was fed (wi t hout appa re nt effect) to chi c ken s an d oth e r :livestock f o r only a few day s; it was n o t realized th at a lengthy latency pe riod was involved (Das et al. 1982; Elhassani 1 9 83). The r e is no effective antidote to co untera c t the e ffects of methylmercu ry on the central nervou s sy stem (Elha ssani 198 3).

Poisoni ng of game bi rd s a nd other wildli fe in Sweden, apparently by seed s treat ed with organ omercu rial s,
wa s noticed i n 1960 (Da s et al 1982). Massive kill s of the grey he ron ( A r de a ci nere a ) in the Nethe r lan d s durin g 1976, were at tributed to a combinatio n of low tempe r at ure s , unde rn ouri s hm ent, and high b ody burd e n s of mercury (Va n der Mole n et al. 1982). Me rcu r y co ntam i nation ha s re sulted in t he clo s ure of ph easant and partri dge h u n t ing area s in Alberta, Ca na da (Mulli ns et al. 1977). In 1967, the Swedish medi cal board b ann e d the sale of fish that contain ed high con c entration s of orga nom ercu ry salts, ori g i nating from a bout 40 la ke s and rivers (Das etal. 1982). In 1970, afte r th e discovery o fhigh levels o fmerc u r y in fish from L a ke St. Clair, Can ada, re striction s on fish ing and the sale of fish we re impo se d in many area s of the United States and Can ada (Da s et al. 1982). Since 19 70, a total of 26 of the 48 States in the conter minou s Unite d States have repo rted me rcury poll u tion in their wate rs as a di re ct re sult of huma n activities. These States h a ve bann ed sport

or co mme rci a l fishing in Hg -co n tamin a te d waters, or h a ve issued h ealth wa rnin g s abo ut the consequ en ce s of eating Hg-co n taminated fi sh or seafo o d from sele cte d wa ter c o urses , or have plac ed res t ric t ions on fis h

con s um ption from ce rtain stream s, lake s, or rivers pol l u ted with me rcury (NAS 19 78). In gene ral, the numbe r of Hg-co n tamin a ted fish an d wildlife habita ts has p r og re ssi vely in cre a s ed --almo st all as a dire ct result of anthro pog eni c activities (Boudo u and Ri beyre 19 83 ).

Most autho riti es on Hg e c o t oxicology ag ree on six poi nts. First, Hg and its co mp ound s have n o kno w n biologi cal fun c tion, and its pre s en ce in li ving orga nism s is u nde sirable an d pote n tially haza r d ous. Second, forms of me rcury with rel a tively low toxicity can be tran sform ed into form s with very high toxicity through biologi cal an d other processe s. Third, m e thylmercury can b e bio c o n ce ntrated in orga nisms a n d biomag nifie d throug h food chai ns, retu rn ing mercu r y directly to man and other u p per tro phi c le vel con s ume r s in co ncentrated form. Fourth, mercury is a mutagen, teratogen, an d carci nog en, an d cau s e s em bryoci dal, cytoch emical, and histop atholo g i cal effect s. Fifth, high body burde ns ofme rcury no rmally enco u n t ered in some spe c ie s of fish and wildlife from remote locatio n s emp h a s ize the compl e xityof natural mercury cy cl es an d huma n impact s on these cycle s . And finally, the anthrop oge nic u s e of mercu r yshoul d be cu rtailed, be cau s e the differe nce b e twe en



### 5tolerabl e natu r al ba ckgroun d levels of mercury an d ha rmfu l effects i n the environ ment is exce ptionally smal l. These, and ot her a s pe cts o f mercu r y and its comp oun ds in the envi r onm ent as a result of anthropog eni c or natural p r o c e s ses, have b een the subje c t of many re vi ews, in cludi ng those by M ontagu e an d Montagu e (1971 ), D'Itri (1 972 ), Fribe r g an d Vostal (1 972 ), Jernelov et al . (1972, 197 5 ) , Keckes a n d Miettinen (19 72), Buhle r (197 3), Holde n (197 3), D'Itri and D'Itr i (1 977), Eisl er (1978, 19 81), NAS ( 197 8), Birge et al. (1 979),.Ma g o s and Webb (1979), Nriagu (1979), EPA (1980, 1985), Jenki n s (1980), Cl arkson and M a rsh (1982), Das et al. (1982), Boudou a nd Ribeyre (1 98 3), Elhassa ni (198 3), Cl arkson et al. (19 84), Ro bin s o n and Touvin en (19 8 4 ) , an d Wren (198 6).

This repo rt was prepa re d in respon se to reque sts fo r in formatio n from enviro n m ental sp eci a lists of the U.S

. Fish an d Wild life Service. it is part of a continuin g se ri es of syno ptic reviews on chemical co ntaminant s and natural re sou r ce s.

SOURCES OF ENVIRO NMEN TAL MER CUR Y
As a dire ct re sult of human activities, me rcu r y levels in river se dime nts have in creas ed fourfol d sin c e precu l tural times, and twofold to fivefold in sedim e n t core s from l a ke s an d est uarie s (Da s e t al. 1982). During the p a st100 years, it ha s been e s timat ed that more than 500,0 00 metr ic ton s ofHg entered the atmosphe re, hydrosphe re, and surfa c e soils, with eve n tual dep ositi on in su bsurf a ce soil s and sedim ents (Das et al. 1982 ). Several activities that contri bute si g n ificantlyto the global inp u tof Hg inclu d e the combu s ti on of fossil fu els; mining a nd rep r o c e ssi ng of gold, cop p e r, and lea d ; operation of chlora l k ali pl an ts; and dispo s al of batterie s and fluo re scent lamps (NAS 1978; Das et al. 1982). Th e atmosp he re plays an imp o rtant rol e in the mobili zatio n of Hg; 25% to 30% of the total atmosph e ric Hg b u rd en is of anthro p o geni c origi n (NAS 1978 ).

In the United States, mercury con s u m pt ion ro se from 1, 305 metri c tons in 1 959 t o 2,359 ton s in 1969 (Tabl e 1). The majo r use of mercury has b een a s a catho de in the ele c trolytic prepa ratio n of chlori ne an d cau s tic (Nri agu 1979). In 1968 this use accounted for about 33% ofthe total U.S. demand for Hg (EPA 1980). Of recent U.S. mercury con s umption, ele c trical ap pa rat u s have a c co unted for ab o u t 27%; industrial and control instru ment s,
su ch a s switches, the r mom e ters, a nd ba romete rs, an d gene ral lab o rato ry applia nce s , 14%; antifouling an d mildew-p roofi ng paint s, 12 %; Hg formul ations to cont rol fungal di seases of see d s, bulb s , an d vegetable s , 5%; and de ntal a m algam s, pul p and pa per manufa c turers, phar ma ceu t icals, metallu rgy and mini n g , and cataly sts, 9% (EPA 1980). Mercury, howev er, is no longer registered for use i n ant ifouling paints, or for the control of fungal di sea s es of bulb s (E PA 1980).

Mercury fro m natural sou r ces ente r s the biosphe re direct ly as a ga s, in lava (from terre strial an d oce ani c volcani c a c tivity), in solution, or in parti culate form; ci nnab ar (HgS ), for example, is a comm on mineral in h o t spri ng de po si ts and a majo r natural so urce of mercu r y (Da s et al. 1982). The gl obal cy cle of Hg involve s dega ssing of the element from the Earth' s cru s t and e v apor atio n fro m natural b o d i es of wate r, atmosp he ric transpo rt (ma i nly in the form of Hg vapo r), and d epo si ti on of Hg ba ck o n to land and water. O c ea nic effluxe s of Hg are tied to equatori a l up welling and p h ytoplan kton activity and may significantl yaffect the global cy cling o f this metal. If volatilization of Hg is p r op ortional to p r i m ary pro d u c tion in the wo rl d's o c ea ns, o c ea nic phytoplan kto n activity represe n ts ab out 36% of the yearly Hg flow t o t he atmosp here, o rabo u t 2,400 tons p e r year (Kim an d Fitzge rald 1 986). Me rcu ry finds its wa y into sedime nts, parti cula rly oceani c se diments, whe r e the retention time can be le ngt hy (Table 2 ) , and where it ma y continu e to contamina t e aquatic o r g anism s (Lind s ay and Dim m ick 1983 ). Estimates of the qu ant ities of Hg enterin g the a t mosph e re from dega ssin g of the surfa c e of the planet vary widely, but a comm only quoted figu re is 30, 00 0 ton s ann ually (Cl a rkso n et al. 1984 ). In aquatic

eco s ystem s , removal of th e sou r ce of anthrop oge nic Hg re sult s in a slo w de cre a se in the Hg content of sedim ents a n d biota (NAS 1978 ). The rate of loss d e pend s, in part

, on the initial degre e of co ntamination, the chemi c al fo rm of Hg, physical and che m ical conditio n s of the syst em, and the h y drauli c turn o v er time (NA S 1978 ).



### 6Table 1 . Industrial a nd ot her u s e s of mercury in the United States in 1959 an d in 1969. All values a r e in m e tric tons (m odifie d from Monta gue an d Mont ague 1 971 ).

1959 1969

–——— —— ——— ———— —— ———— Use Tons Percent Tons Percent

Chlo ral k ali proce ss 201 15.5 716 30.4
Electri c al ap p a ratu s 308 23.6 644 27.3 Antifouling an d mildew p a in ts 121 9.3 336 14.2
Control devices 213 16.3 241 10.2 Dental p r ep arations 63 4.8 105 4.5 Catalyst s 33 2.5 102 4.3 Agriculture 110 8.4 93 3.9
Labo rato ry 38 2.9 71 3.0
Pharma ce uticals 59 4.5 25 1.1 Pulp and pa p e r mill 150 11.5 19 0.8 Metal amalg a m ation 9 0.7 7 0.3 Total 1,305 2,359

Table 2. Amount of mercu r y in some gl obal re se rvoirs (N AS 1978 ), and re siden ce time (Clarkson et al. 19 84).

Hg content Re side n c e Re serv oi r (metri c ton s ) time

Atmosph e re 850 6 to 90 days Soils 21,000,0 0 0 1

, 0 0 0 y e a r s Fre s h w ater 200

- Fre s h w ater bi ota (living) 4 - Oce an water 4,150,00 0,00 0 2,000 years
Oce ani c biota (living) 3 - Oce an sedim ents 330,00 0,000, 000 >1 million ye ars

CHEMI CAL PROPERTIE S Mercury, a sil v er-white met a l that is liqui d at room te mperature a n d is highly vol a tile, can exist in three
oxidation stat es: eleme n tal mercury (Hg o ), mercu r ou s ion (Hg 2 2+ ), and mercuri c ion (Hg 2+ ). It can be pa rt of both inorgani c and organic co mpounds (EPA 1980; Clarkson et al. 1984; Tabl e 3). All mercury compounds interfere with thiol metaboli s m, ca usin g inhibition o rin activation of protein s cont aining thiol lig and s and ultimately leading to mitotic distu r ba nce s (Das et al. 1982; Elha ssani 198 3). The mercu r ic speci e s i s the most toxic inorg ani c ch emical form, but all three form s of inorga nic Hg m a y have a co mmon mole cular me ch ani sm of damag e in which Hg 2+ is the toxic sp eci e s (Cla rkso n and Ma rsh 19 82; Figure 1).

Chemi c al spe c iation i s pro bably the mo st importa nt variabl e influe ncin g ecotoxicolo g y of Hg, but Hg spe c iatio n is difficult, espe cially in natural environ me nts ( Boudou and Ri beyre 1983 ). Mercury com pou n d s in an aque ou s sol u tion are chem ically com p le x. Dependin g on pH, al kal i nity, redox, and other va ria b les, a wi de



### 7variety of chemical species are liable to be formed, hav ing different electri c al ch arges and sol ubilities. For example, Hg Cl 2 in s o lution c an s p ec iat e into Hg(OH) 2 , Hg 2+ , HgCl + , Hg(OH) - , HgCl 3 - , and Hg Cl 4 2- ; anionic forms p r ed o m inate in sali ne enviro n me nts (Bou dou and Ri beyre 1983 ). In the aquatic e n vironment, und e r naturally o c curri ng conditi ons of p H an d temperature, Hg may also become me thylated by biologi cal or ch emical processes, or both (Beijer and Jernelov 1979; EPA 1980; Ram a m oorthy and Bl umhagen 1984; Figure 1) -- althoug h abio l ogical methylation is limite d (Calli ste ra nd Winf rey 1986). Methyl mercury is th e most ha za rdou s mercury spe c ies du e to its high sta b ility, its lipid sol ubi lity, and its possessio n of ionic prope rtie s that lead to a high ability to penetrate me mbra ne s in living orga nisms (Beije r an d Jernelov 19 79).

All mercu r y di scharged into rivers, bay s, or estu ari e s a s eleme n tal (metallic) mercury, ino r ga ni c divalent mercury, phe nylmercury, o ralkoxyal k yl mercury can be co nverted into me thylmercury compo und s by natural pro c e s ses (Jernel ov 1969 ). The mercury methylation in eco s ystem s dep end s on mercury load ings, micro b i a l activity, nutrient content, p H and redox con d ition, su spend ed sedi ment load, se di mentation rates, and oth e r variable s (NA S 1978; Com peau a nd Bartha 1984; Berman and Ba rtha 198 6; Calli ster an d Winf rey 1986; Ja ckso n 198 6). The findin g that ce rtain microorgani sms are able t o conve r t inorgani c and o r g anic forms of Hg into the highl y toxic methylmercury o r di methylmercu ry has made itclear that an y form of Hg is highly ha za rdou s to the environment (EPA 1980, 1985). The synthesi s of methylmercury by bacteria from inorgani c Hg comp oun ds p r esent in the water o rin th e sedim ents i s the majo r source of this molecule in a quatic environ ment s ( Boudo u and Ribeyre 1 9 8 3 ). This p r o c ess ca n occu r unde r both aero b ic a nd a naerobi c
con d ition s (B eijer an d Je rn elov 1979; Cl arkso n et al. 1984 ), but se ems to favor anae robi c co ndition s (Ol s o n and Coo per 1 976; Calliste r and Winfrey 19 86 ). Tran sform a tion of inorg anic me rcury to an orga nic form by bacte ria alters it s biochemical re act i vity and hence its fate (Wi n dom and Ke n dall 197 9; Figure 1 ) . Methylmercury is decompo se d by bacteri a in two pha se s. First, hydroly t ic enzyme s cleave the C-Hg bond, rel e a s ing the meth yl grou p. Seco nd, a redu cta s e en zyme converts the io nic Hg to the elemental fo rm, which i s th en free to diffuse from the aqu atic enviro n m ent into the vapor p h a s e. These dem ethylating microbe s app ear t o be wid e spread in the environ m ent; they have been i s olat ed from water, sedim ent s, and soils a n d from the gast r ointe s tinal tract of mammal s --in cludi ng hum a n s (Cla rkso n et. al. 1984).

Table 3 . Some pro pertie s of mercu r y a nd its co mpo und s. a

Elemental Mercurou s Mercuri c Methylmercu r y Prope rty mercury chlo ride chlo ride chlo ride

Empirical formula Hg Hg 2 Cl 2 Hg Cl 2 CH 3 HgC l

Molecula r wei ght 200.59 472.09 271.52 251.09 c

Chlo rine, % 0 15.02 26.12 14.12 c
Mercury, % 100 84.98 73.88 79.89 c
Melting point, o C –38.87 sublim es at 277 170 c

400– 500

Den s ity 13.534 7.15 5.4 4.063 c Solubility, mg/L (ppm )

In water 0.056 2.0 74,070 ~1,01 6 d

In benzen e 2.387 b insol. 5,000 ~6,53 5 e

a All data fro m Merck Ind e x(1976 ), except whe r e ind i cated.
b Spenc e r and Voigt (1968). c Wea s t and Astle (19 82).
d Eisle r(un p u b l.), 72 h equi librium value. e Eisler (unp ubl .), 24 h equili brium valu e.



### 8Methylmercu ry is produ ce d by methyl ation of inorg ani c mercu r y pre s ent in both fresh w ate rand saltwate r sedim ents, a nd accum u lat e s in aq uatic food ch ain s in wh i c h the top-level p r ed ators u s u a lly contai n the hi ghe st

con c e n tration s (Clarkson a nd Marsh 1 9 8 2 ). Orga nom ercury compo und s other th an methylmercury de co mp ose rapidly in the environ ment, and be have much li ke ino r gani c Hg co mpoun ds (Be ijer and Je rne l ov 1979). In orga nisms n e a r the top of the food chain

, such a s carn ivorou s fish es, almo st all Hg a c cumulat ed is in the methylated form, prima r ily as a re sult of the con s um pti on of prey co ntaining meth ylmercury; methylation also occurs at the orga nism level by way of muco us, in te stinal ba cteri a , and en zymatic pro c e s se s, but these pathways are not as impo rtant as diet (Huckab ee et al . 1979; Boud ou and Ribey re 198 3).

The biolo g ica l cycle of Hg i s deli c ately b a lan c ed, an d small chan ge s in input rate s and the che m ical form of Hg may re sul t in increa se d methylation rates in sen s itiv e system s (NAS 1978 ). For exam pl e, the acidifi c ati on of natural b odie s of freshwater is stat istica lly asso ciate d with elevated con c entratio n s of methyl mercury in th e edible tissu e s of predato r y fishe s (Cl a rkson et al. 1984 ). In chemica lly sensitive wa terways, su ch as po orly buffered la ke s, the com b in ed effects of acid p r e c ipita t i on and in cre a se d emissio n s of Hg to th e atmosp he re (with sub s e que nt depo sition) p o s e a serio u s t h reat to the bi ot a if optimal biomethylatio n con d ition s are met (NAS 1978 ).
Mercury bin d s strongly wit h sulfhydryl g r oup s, and h a s many poten tial target site s duri ng em bryogene si s; phenylme r cury and methylmercury com poun ds a r e a m ong the st ro nge st kno w n i nhibitors of cell division (Bi r ge et al. 1979). Orga nom ercu ry comp oun d s , esp e ci ally me thylmercu ry, cross pla c e n tal barriers a nd ca n enter mammal s by way of the re spiratory tra c t

, gastrointe s ti nal trac t, sk in, or muc o us me mbrane s (Elhassani 1 9 83). Whe n com p a r ed with in org anic me rcury comp oun ds, orga nom ercu rials a r e mo re completely a b so rbe d , are
more solu ble in orga nic sol v ents and lipi d s, pa ss m o re readily thro ugh biol ogical membra ne s, and are slo w er to be excreted (Clarkson a n d Marsh 198 2; Elhassani 1 9 83; Gre ene r and Kochen 1983 ). Biological me mbra nes, inclu d ing tho s e at the blood -brain interfa c e and pla c e n ta, tend to discrimi nate ag a i nst ioni c and inorg ani c Hg, but allow rela tively easy passage of met h ylmercury a nd dissolve d Hg vapo r (G reene r and Ko che n 198 3). As judge d by membra ne mod e l studie s , it appea rs that el ectri c ally neut ral mercu r ial s are re sp on si ble for mo st of the diffusion t r an spo r t of Hg, although th is moveme nt is modified si gnifica ntly by pH an d Hg sp eciatio n . It

seem s, ho we ver, that the liposolubility of methylmercu r y is not the e n tire re ason for its toxicity and do es n o t play a major role i n its tran spo r t. This hypoth e si s nee ds to be examined further in stu d ies with living membrane s ( Boudou et al. 1983).
Mercury

- anta goni stic drug s incl ude 2,3

- dimerca p topropan ol , polythiol re sin s , se lenium salts, vitamin E, and sulfhydral ag ents ( in J.O. Nria gu (ed.). The biog eo ch emistry of me rcu r y in the e n vironm ent. Elsevier/ N ort h

Holla nd Biom edical Pre ss, Ne w York.Ma gos a nd Web b 1979; Elha ssani 1 983 ). Thiols (R-SH), whi c h compet e with Hg for p r otein bindin g sites, a r e the most impo rta n t antagoni st s of inorg ani c mercury salts, and have b een
use d extensiv ely in attempts to cou n tera ct Hg poi so ni ng in huma n s (Da s et al. 1982). The p r otective actio n of sele nium (Se ) again s t adv erse or leth al effects ind u ced by inorg a n i c or o r ga nic mercury salts has be en re p o rted for algae, aq u a tic inverteb rates, fish, an d mammal s (Mago s and Web b 197 9; Hei s ing e r 19 79; Cha ng et al. 1981; Lawren c e a n d Holo ka 1 9 8 1 ; Das et al. 1982; Got s is 1982; Eisle r1 985; Satoh etal. 1985). Selenite salts can relea s e m e th ylmercury fro m its linkag e to protein s , an d there is g e n e ral ag re eme n t that a true antago nism e x ists betwe en Se a nd Hg, altho u gh the exact mech ani sm is not fully establish ed (Da s et al. 1982). In marin e mammal s an d human s, for example, Se and Hg co ncentration s a r e closely relate d, almost line a rly in a 1:1 molar ratio, but this relation bl urs in teleost s (in whic h Se is abun dant) a n d fails in bird s (Eisler 1 985 ).

MERCURY IN MINAMAT A , JAPAN
One of the ea rliest an d mo st ext ensivelydocum ented ca se s of mercury poi so nin g occurre d in the 1950' s at Minamata Ba y, in southwe s tern Kyu s hu, Japa n--e spe c ia lly amon g fishe r me n and their families (Fujiki 1 963, 1980; Iru k aya m a 1967; Mat i da and Kum ada 19 69; Ko jima and Fujit a 1973; NAS 1978; Elha ssani 198 3; Nishimu r a an d Kumagai 1 983; Doi et al . 1984). The sou r ce of the mercury was in wa ste discharg ed from an acetal dehyd e plant that used inorgani c Hg a s a catal y st; between 1932 a nd 19 6 8 , Minamata Bay receive d at least 26 0 ton s of mercu r y, and pe rha p s as mu ch a s 6 00 tons. A se vere neu rol o g i cal di sorde rwa s re cog n ized in late 1953 a n d had rea c h ed epidemi c p r o portion s by 1 956; 111 ca ses of poi soni ng we re repo rted by the en d of 1960 a nd 41 death s by August 19 65. By 1982, there were 1,800 v e rified hu man victims of mercu r y poi soni ng in a total region al popul ation of 200,000; h o weve r, the tota l numbe r o fvictims rem a ins u n confirmed. Symptoms eviden ced byhuman victi m s incl ude d sensory impai rment, co n s tri c tion of visual fields, heari n g loss, ataxia, and



### 9spe e ch distu r ban ce s. Con genital cases were acco mp anied by di sturba nce of ph ysical a nd me ntal develop ment; about 6% of babie s bo rn i n Minamata h ad ce reb r al p a lsy (vs. 0.5 % elsewhe r e).

"Minamata di sea s e" resulted from the di scharge of m e thylmercury from ch emica l factorie s into Minamata Bay. Once di luted and diff use d in the water, it was conc entrate d to a high level in fish and filter-fe edin g sh ellfish by several ro utes, incl udin g biocon centration and foo d c hai n biom agnification. Whe n these fish an d sh ellfish

were co nsum ed by human s, methylmercury g r ad uall yaccu mulate d to exceed a thresh old val ue, cau s in g intoxication. Spontane ou sl y poison ed cats, dog s, rat s , wate rfowl, and pig s be h a ved erratical l y and died; flying

cro w s and g r ebe s su dde nl y fell into the sea a nd drowned; and la rg e numbe rs of dead fish we re see n floatin g on the sea surfa c e (Doi et al. 1984 ). In laborato r y studie s , cats a nd ra ts fed shellfi s h from the Ba y developed t he

same sign s a s those se en in animal s affected spo n ta neou sly. Abnormal Hg con t ent--i.e., more than 30 mg/ k g fresh weig ht--wa s mea s u r e d in fish, shell f ish, and mud s from the Ba y, and in orga ns of ne cro p sied huma n s a nd cats that ha d su ccumbe d to the dise ase

. Mercu r y co nt amination o f fish and se d i ments was st ill evident in 1981, althoug h discharg e s from the acetalde h y de plant ce a s ed in 1 971 (Doi et al. 198 4).

There is a st rong rel a tion b e twee n the food of bird s fro m Minamata and the Hg c ontent in feathers; the conte n t is hig hest in fish -e ating se abird s and lo we st in herbivo ro us waterfo w l (Doi et al. 1984; Table 4). Th is

same relatio n held in bird s colle cted fro m China a nd Ko rea, altho u gh co ncentrat i ons were sig n ificantly lower (Doi et al. 19 84). The r e are clo s e correl ations b e tw e en Hg conte n t s of zoopl an kt on an d su spend ed pa rticulate matter, and o f sediment s a nd fish mu scl e, sugg estin g a pat hway from sedi ment to fish by way of susp end e d matter and zo oplan kton. The co nversio n from inorga nic Hg to methylmerc ury is believed to h a ve occurre d prima r ily in zoopla n kto n (Nishimu ra an d Kumagai 1 983).

Table 4. Mercury con c ent rations in sele cted biol ogi ca l and non biol ogical materi als colle cted from Mina mat a Bay, Japan a nd enviro n s. Con c e n tratio ns are in mg Hg /kg (pp m ) f r esh wei ght (FW), o rdry weight (DW).

Sample, year of colle ction, an d Con c e n tratio n other vari able s (mg/kg) Refere nce a

Ph yt oplankton

1974 Max. 0.32 DW Nishimu r a an d Kumagai 1 9 8 3
In v e rtebra te s 1961
Coel enterate s 9.6 DW Matida and
Tunicates 35–5 6 DW Kumada 1 9 6 9
Molluscs
P a cif i c scall o p , Chlam y

s ferrei nippo nen si s Soft parts 48 DW
P a cif i c oy st e r , Cra s so stre a giga s Soft parts 10 DW; 5.6 FW
C l a m , Horm om ya m u tabilis
Foot 18–4 8 DW Fujiki 19 63 Gangli o n 181 DW



### 10Other tissu e s 20–7 3 DW
C r us tac e an C r a b

, Neptu n u s pel agi cu s M u s c l e 3 9 D W
Filter-fee ding molluscs
Soft parts
1962 Max. 43 DW Fujiki 19 80
1963 Max. 40 DW
1965 Max. 35 DW
1967 Max. 60 DW
1969 Max. 16 DW
1971 Max. 16 DW
1972 Max. 4 DW Zoopla n kto n 1974 Max. 1.1 DW Nishimu r a an d Kumagai 1 9 8 3
Fish
1961 Larg e scal e bl ackfish, Girella punc tata
Visce ra 18–2 7 DW Matida and
Muscle 12–2 0 DW Kumada 1 9 6 9
Scarbre a st tu skfi s h,
Cho e ro don a z uri o Muscle 309.1 DW Fujiki 19 63
Liver 85.0 DW
Hea r t 36.4 DW
Gill 13.3 DW Dige stive gla n d 1.3 DW
B l ack p o r g y , Sparu s m a croce phalus Muscle 16.5 DW
Liver 32.2 DW
Hea r t 18.3 DW
Gill 9.1 DW Dige stive gla n d 4.0 DW
Muscle
1961 23.0 DW Fujiki 19 80
1963 3.5 DW
1965 11.5 DW
1966 –72 <0.6 DW
1974 Max. 0.6 FW Nishimu r a an d Kumagai 1 9 8 3
Birds



### 111955 –80
Feathe r Fish -eatin g seabirds 7.1 DW Doi
Omnivorou s waterfo w l 5.5 DW et al. 1984
Predato r s 3.6 DW
Omnivorou s terrestri a l bird s 1.5 DW
Herbivorou s waterfo w l 0.9 DW
1965 -66, fou nd dea d
Feathe r 4.6–13.4 F W Kojima and Fujita 1973
Mammals Cat, Felis dom e sticus , 19 61
H a i r Naturally poisoned 40–5 2 DW Jen k in s 19 80 Experimentall y poison e d 22–7 0 DW
Sea w ater
1961
Total 0.0016–0.0036 FW EPA 1980
1974
Filtered 0.0001 F W Nishimu r a an d Suspe nde d p a rticul ates 0.0000 75 FW Kumagai 1 9 8 3
Mud
1963 28–7 13 DW Fujiki 19 80
1969 19–9 08 DW
1970 8–25 3 DW
1971 14–5 86 DW
Sediments
1973 >15 –60 0 DW Nishimu r a an d Kumagai 1 9 8 3

a Each refere nce a pplie s to the values i n the same ro w and in the rows that follow for which n o other refere nce i s indicated.

In aquatic e n v ironme n ts where p o int so urces of in d u s trial contami nation have b een ide n tified , the elimination ofHg disch a rg es ha s u s uall yimproved e n vi ronm ental quality. Such improveme n t has be en re p o rted for Minamata Bay (Table 4 ) ; for sedime nts in Sague na y Fjor d, Queb ec, wh en chlo ralkali wa ste s were limite d ; for fish re sidu es i n Can ada' s L a ke St. Clair after two chlo ralkali plant s were clo s e d ; and in vario u s se ction s of Europ e and North Ame r i c a whe n indu strial discha rg es were eli m i nated (Ba r be r et al. 1984).

BA C K G R O U ND CO NCE N T RA TIONS

GENERAL Mercury bu rd ens in sedim ents an d othe r nonbi ologi cal ma terial s a r e estim a ted to have increa sed u p to 5X preh uma n levels, prim arily as a re sult of man' s acti vities (NAS 197 8). The re sid ence time of mercury is comp aratively short (a bout11 days) in t he atmosphe re, but is much longe r (at le ast 1,000 yea r s) in oceani c waters, soils, and sedime nts (Clarkson 1 984).



### 12An elevated concentratio n of mercury (i. e ., >1.0 mg/k g fresh weig h t ), usually as methylmercury, in any biologi cal sa mple is often asso ciated wi th proximity to human u s e of mercury. The elimin ation of Hg poi n t

sou r ce disch a rge s ha s u s ually been su ccessful in im provi ng e n vironmental q u a lity. Howeve r, elevated levels of mercury in bi ota may persi st in conta m inated area s l ong after the sou r ce of poll u tion ha s bee n discontin ue d (Ra da et al. 1986). Fo r example, Hg re mains el evated today in re side nt biota o f Lahontan Rese rvoir, Nevada, whi c h re ceive d about 7,50 0 tons of mercury as a resul t of gold and silver mini ng operation s du ring the pe rio d 1865 to 18 95 (Co ope r 19 83 ). It is noteworthy that so me gro u p s of orga nisms with con s i s tently elevated Hg resi due s mayhave acq u ire d these con c entration s a s a result of natural p r o c e s se s, rathe rthan from anthro pog eni c activities. T hese gro u p s inclu de olde r spe c ime n s oflong-lived p r edatory fish e s , marin e mammal s (e speci a lly pinni ped s), and o r gani sms livin g near n a tura l Hg-o re -ci n n abar d epo sits.

NO NBIO L O G ICA L Mercury bu rd ens h a ve increased 2X to 5X pre c ultura l levels in freshwate rand e s tuari ne sedi ments an d fresh w ate rla ke s and rive rs, but estimat ed increa se s in oce ani c wa ters an d terre s trial soils h a v e been ne gli g ible (NAS 197 8). Total mercu r y con c entratio n s in un co nta m inated natu r al waters (pre suma bly unfiltered ) no w ra nge from abo ut 0.001 to 0.050 ug/l (Tabl e 5). In sediment s that we re a n throp oge nically contamin ated with Hg,

con c e n tration s we re signifi cantly elevate d (usua lly >2 0.0 mg/kg ) when compa r e d with un cont aminated sedim ents (u sually <1.0 mg/kg). The re side nce time of Hg in non b i ologi cal mate rials i s varia b l e , and dep en ds on a numb e r of physicoche m ical conditio n s. Estimate d hal f-time re side nce value s for Hg are 1 1 days in the atmosp he re, 1,000 years i n terre strial soils, 2,100 to 3,200 years i n oce an wate rs , And >250 million years i n
oce ani c se di ments (NAS 1978, a s quot ed in Boudo u and Rib e yre 1983 ); the est i mate wa s 1 month to 5 years for wate r fro m the contam inated Sagu e nay River in Queb ec (Smit h and Lo ring 1981 ).

Table 5 . Mercury con c ent rations in wate r and sedim e nts.

Material (unit s ) Con c e n tratio n Referen c e a

Wa ter (μg/L ) Open o c e a n 0.0053 + 0.0022 Nishimu r a et al. 1983

Open o c e a n <0.01 Fitzge rald 1 9 79
Coa s tal sea w ater <0.02
Estuari ne sea w ater <0.05

Rivers and la ke s 0.01 (Max. 0.05)
Rain wate r Open o c e a n 0.001
Coa s tal o c ea n 0.01
Contin ents Often >0.05
Sediment inte rstitial

water 0.1
Glaci a l wate rs 0.01
Grou nd waters 0.05 Sediments (mg/kg)
Contami nate d area s Near chl o ralkali plant Queb ec, Can ada 12.0 Smith and Lo ring 19 81 Norway 250 (9 0.0–3 5 0 .0) Skei 197 8
Thailan d 8.4–58.0 Suckch aroen and
Lode niu s 198 0



### 13Nea r gold mi ning operation s South Da kota 0.1–4.1 Martin an d Hartman 1 984
Australi a 120.0 Bycroft et al. 1982
N e ar H g

- f u ngic i d e plant
Denm ark 22.0 Kiorbo e et al. 1983
Nea r acetald ehyde plant
Minamata Ba y, Japan 28.0–7 13.0 Skei 197 8
Nea rpulp a n d pape r mill
Finland 746.0 Paasivirta et al. 1983
Un contami n a t ed area s North Cent ral U.S. 0.02–0.0 6 Martin an d Hartman 1 984 (Max. 0.11)
South Da kota 0.02–0.1
Thailan d 0.03 Suckch aroen and
Finland 0.02 Lode niu s 198 0
Variou s la ke s Usually <1 0.0

, Skei 197 8 freque ntly <1.0

a Each refere nce a pplie s to the value in the same ro w and in the rows that follow for which n o other refere nce i s indicated.

Levels of me rcury in sedim ents may be reflected by a n increa sed mercury cont ent in epibe nthic faun a. For example, Hg con c e n tration s in se diment s nea r the Hy perio n se we r outfall in Los Angele s , whi c h ra nge d up to 820 ug/ kg an d decrea s e d with increa sin g distan ce fro m t he outfall, were refle c te d in the Hg content of crab s, scallop s , and whel ks. Con c entration s of Hg we re hi g hest in organi sm s colle cted neare s t the d i scharge, and lowe st in those colle cted te ns of kilom e ters a w ay (Kle in and Gol d b e rg 19 70 ).

B I OLOGICAL
Information o n mercury residue s in field colle ction s of living orga nisms is e s pe cia lly abundant; accordingly, only a few sel e cted d a ta po ints are sho w n in Table 6. Additional, m o re exten s ive

, information wa s given by Jen k in s (1 98 0), Eisler (19 81), and Wre n (198 6).
In general, mercury con c e n tration s in bi ota were us u a lly <1.0 mg/kg fre s h weig ht tissue in o r gani sms colle cted fro m location s n o t directly affected by man ' s u s e of the element. Ho wever, they e x ceed 1.0 mg /kg-- and are so me times ma rke d l y higher--in a n imal s a nd vegetation fro m the vicinity of chloralkali plants; ag ricu ltural

use r s of me rcury; smelte rie s ; mining op e r ation s ; pulp and pa per mil l s; factori e s p r odu cin g Hg -contai ning p a i nts, fertilize r s, an d inse ctici d e s ; sewe r outfal l s; slud ge di sposal are a s; and othe r ant hrop oge nic p o int sou r ces of mercury. (Se v eral notabl e exceptio ns to this gene rali zation a r e di scu s sed later. )

Certai n sp eci e s of ma cro p h ytes strongl y in fluence m e rcury cy cling

. For exampl e, Spartina alterniflora

-- a domina n t saltmarsh plant i n Georgia e s tuarie s--a ccou nted for almo st half the total mercury bu dget in that

eco s ystem (Wind o m et al. 1976). Man g rove vegetat ion plays a si milarly impo rtant role in me rcu r y cycli ng i n the Florid a Everg l ade s (Tri pp a nd Ha rri ss 19 76). The s e finding s sugg e s t that more rese arch is n e eded o n the role of higher pl an ts in the mercury cycle.



### 14Mercury was detecta ble in the tissu es ofalmost all fre s h w ater fishe s examine d , with the majo rity of the Hg ( > 80 %) pr es en t a s me th ylme rc u r y ( Hu ckab ee et al. 1 979). Methyl mercury is a b s orbed m o re efficiently than inorg ani c Hg from wate r, a nd pro bably from food, and is retain ed lo nger reg a rdl e ss of the upta k e path w ay ( Huckab ee et al. 1979). Rese rvoir con s truction h a s o ften been infe rre d to be a cause of eleva t ed mercury

con c e n tration s in fish. It is hypothe sized that increa se s in mercu r y levels ob se rved in fish were due to ba cterial methylation o fnaturally occurrin g Hg in the flooded so ils (Bo daly e t al. 1984). Other facto r s th at enhan ce accumul a tion of Hg in pred atory teleost s from re cently create d re se rvoirs incl ude low pH, hig h humu s conte n t, and lo w biop rodu ction (L od eniu s 198 3; Lodeni us et al. 1983). In ge neral, me rcury levels are hi gher in fish from younge r oligo t rophi c re se rvoirs, an d lower in fish fro m ol der eut rop h ic re se rvoirs; in both situa t ions, tissue Hg levels u s uallydeclin e as th e reservoi rs a ge (Abe rnath y and Cumbi e 1977 ). Con c entration s >0.5 mg/kg (bu t <1.0 mg/kg ) fre s h weig ht have been repo rte d in trout fro m se veral wil dern e ss la ke s in north ern Maine (A kiela s zak and Haine s 1 981) a nd fro m the Adiron dacks regi on of New Yo rk (Sloan and S c hofield 19 83); these value s are
con s id era b ly highe r than m i ght be expe cted for fish in habiting remo te lake s. The s e elevate d concentratio n s were usually asso ciated wi th lake s of low pH, lo w cal c iu m, low di ssolved o r ga ni c ca rbo n co n c entration s, and low water h a rdne ss a nd al kalin ity.

Table 6 . Mercury con c ent rations in field colle ction s of sele cted spe c ies of flora an d fauna. Valu es sho w n are in mg Hg/ k g fre s h weight (F W), or d r y we ight (DW).

Taxonomi c group, org ani sm, Con c e n tratio n a
tissu e, and ot her vari able s (ppm ) Referen c e b

Fungi, Liche n s, Mosse s, Plants
Manda rin o r a nge, Citru s ta chib ana Jap an Spray ed with Hg
Fruit skin 0.03–0.2 4 FW Jen k in s 19 80
Fruit pulp 0.01-0.4 F W
U n s p r a y e d
Skin and p u lp 0.01–0.0 5 FW Fungi, Cortinarius sp p. Nea r sm elter 9.5–35.0 DW Moss, D i c r

anu m s c o p a r ium , whole
Tenne ssee Exposed to fly ash 1.1 DW
R e mo te ar eas 0

. 1 D W
Great Smo ky Mountain s 0.07 DW
Ha waii 0.16 DW
Icelan d 0.03 DW
Wate r hy acint h

, E i chho rnia cra s sipe s From se wage lagoon in Bay St. Louis, Missi ssip p i
Leave s 70.0 DW Chig bo et al. 1982
Lich en, Hypogym n ia ph ysode s , whol e Finland, 19 82 –83
Dis t ance, in km, from
chloral k ali plant



### 150–1 18.0 FW Lode niu s and
1–5 2.0 FW Tulisal o 198 4
5–20 0.4 FW
20–1 00 0.3 FW

> 1 0 0 0

. 3 F W
Labrado r tea, Ledum s p

. Alaska, over cinn aba r dep osit
Stem 1.0–3.5 DW Jen k in s 19 80
A l f a l f a , Medicago sativa
From soil co n t aining 0.4 pp m Hg
Root 90.0 FW
Leaf 0.13–0.4 F W
From soil wit h <0.4 ppm Hg
Leaf 0.16 FW
Toba cco, Nicotiana taba cu m Leaf
Treate d with Hg (Jap an ) 1.0–1.6 F W
Untreated (USA) < 0 .2 FW
R i c e , Or yz a s a t i va , grai n Sprayed with Hg 0.1–0.7 F W
Un sprayed 0.02–0.1 F W
Marin e flowe r ing plant,
Posidonia o c ea nica
Nea r se we r o u tfall, Marseilles, France
Rhi z ome s 2.5 DW Augier
Leave s 51.5 DW et al. 1978
Root s 0.6 DW
Che rry , Prun us a v ium Europ e (Slov enia), ba rk
Un contami n a t ed area s 0.06 FW Jen k in s 19 80 High Hg in so il 6.0 FW
Facto r y area 59.0 FW
M o s s e s , Sph agnum spp., whol e Finland, 19 82 –83
D i s t a n c e ( k m ) f r o m chloral k ali pl ant
0–1 3.8 (1.5–1 6.0 ) FW Lode niu s and
1–5 0.8 (0.2–2.6 ) FW Tulisal o 198 4
5–20 0.09 (0.04 –0. 2) FW
20–1 00 0.05 (0.0– 0 .8 ) FW

> 1 0 0 0

. 0 2 F W Aqua tic Inv e rtebr a te s



### 16F r es hw a t e r Annelids, 2 families
From Hg-co n taminated a r e a s 0.3–0.6 F W Hu ckabe e From u n co ntaminated a r e a s 0.03–0.0 5 FW et al. 1979
Ar th r o po ds
Sow bug, Asellus sp. Swede n, who l e 20 km bel ow pape r mill 1.9 FW Jen k in s 19 80
1–15 km abo ve paper mill 0.06 FW Crustaceans, 2 families
From Hg-co n taminated a r e a s 1.9–10.0 F W Hu ckabe e From u n co ntaminated a r e a s 0.06–0.5 6 FW et al. 1979 Insects, 8 families
From Hg-co n taminated a r e a s 0.5–5.0 F W
From u n co ntaminated a r e a s 0.05–0.2 1 FW Stonefly, Isoperla sp. Whol e, Swed en 17 km bel ow pape r mill 2.4 FW Jen k in s 19 80
15 km ab ove pape r mill 0.07 FW Crayfish, Orcone ctes virili s Ontario, whol e Central lo cati on 0.09–0.4 9 FW
F r o m c h l o r a l k a l i plant locatio n 1.4–7.4 F W Crayfish, Pacifias tacus s p

. Laho ntan Re servoi r, Neva da,
1981
Abdomen 5.7 FW Coo per 1 983
Molluscs
From Hg-co n taminated a r e a s 0.02–2.1 F W Hu ckabe e From u n co ntaminated a r e a s 0.05 FW et al. 1979
Marine
Annelid s, wh ole, 3 spp. Georgia, US A, estuarie s Hg-co n tamin a ted estu ary Total Hg 0.7–4.5 DW Wind om and Methyl Hg Max. 0.8 DW Kendall 19 79
Control estu a r y Total Hg 0.1–0.6 DW
M e t h y l H g M a x

. 0

. 1 3 D W
Ar th r o po ds
Cru s ta cea n s, whole, 2 spp

. Georgia, US A, estuarie s



### 17Hg-co n tamin a ted estu ary Total Hg 0.4–1.8 DW Methyl Hg Max. 1.0 DW
C o n t r o l e s t u a r y Total Hg 0.1–0.4 DW
M e t h y l H g M a x 0

. 0 5 D W
American lob s ter,
Hom a rus a m erican us M u s c l e Che s a pea ke Bay 0.03–0.0 6 FW Jen k in s 19 80
NW Atlanti c 0.25–1.6 DW
Nova Scotia 0.15–1.5 F W
S p i n y l o b s t e r , Nephrop s n o rvegi cu s Tyrrhe n ian S ea, 1981
Muscle 2.9 FW Schreibe r 19 83
S h r i m p Edible portions
Total Hg 0.77 FW Cap pon Methyl Hg 0.4 FW and Smith 19 82
Echino de rms Sea stars, 3 spp., 1981 Venezuela, p o lluted area Gona ds 3.8–8.7 DW; Iglesia s an d
0.9–1.6 F W Pancha szad eh
1983
Molluscs
From vicinity chlo ral k ali pla n t, Israel, 19 80– 82, soft part s G a s t r o p o d

, Arcula ria gib bosula 18.2–3 8.7 DW Hornun g et al. Bivalve, 1984
Donax ve nu stus Max. 6.4 DW
Bivalves

, s o ft parts
From Hg-poll u ted are a , D e n m a r k Depo sit feeders 1.4–4.4 F W Kiorbo e Suspen sion feeders 0.9–1.9 F W et al. 1983
Edible portions
Total Hg 0.04–0.2 2 FW Cap pon a nd Methyl Hg Max. 0.09 FW Smith 1982
Soft parts, 2 spp. Georgia, US A, estuarie s



### 18Hg-co n tamin a ted estu ary 0.5–1.2 DW Wind om and
Control estu a r y 0.1–0.2 DW Kendall 19 79
M u s s e l

, Mytilu s californi an us Soft parts
Nation wide <0.4 DW Flegal
California 0.6–2.5 DW et al. 1981
M u s s e l

, Mytilu s ed ulis
Soft parts
B e l g i u m 1

. 0 D W Spain 1.5 DW
Ne w Brun swi c k 0.1 FW
Nethe r lan d s 0.1–0.3 F W
Great Britain 0.02–0.7 F W
Ne w Zeala n d 0.02–0.4 8 FW Norway 0.2–0.65 DW
Softs hell c l am, Mya arena ria
Soft parts Che s a pea ke Bay, MD 0.01–0.0 5 FW
Nova Scotia 0.03–0.1 3 FW
N e w B r u n s w i c k
3 km below pulp mill 0.9 FW
3 km belo w chloral k ali plant 3.6 FW
Terres t rial Inv e rtebrates Aphid, Macro s iphium gei
Whol e, Illinois
Fed on Hg-treated tomato plants 0.3–11.5 F W
Control 0.08–0.8 1 FW
Lacewi ng, Ch r y

s o pa ca r nea Whol e, Illinois
Fed on Hg-treated 0.6–31.4 F W

tomato plants
Control 0.0–1.1 F W
Fish
Ro ck b a s s , Am bloplites ru pestri s M u s c l e Ontario 0.6–4.6 F W Michig an 0.4 FW
We stern Ont a rio 1.1–10.9 F W
Lake St. Clair 0.5–2.0 F W
Blue hake, Antimora ros t rata
NW Atlanti c , 2500 m de pth



### 19M u s c l e 1880 0.51 FW Barbe r 1970 0.34 FW et al. 1984
F r es hw a t e r dr u m , Aplodin o tus
grun nien s Whol e Age 0 0.05 FW Busch 198 3 Age I 0.13 FW Age II 0.18 FW
B l ackt ail, Di pl

odu s sa rgu s , musc le Hg-pollute d a r ea 0.3–1.7 F W Hornun g Unp o lluted a r ea 0.04–0.6 4 FW et al. 1984
Northern pike, Esox lu cius , m u s c l e Swede n 0.2–9.8 F W Jen k in s 19 80 Queb ec 0.3–0.8 F W Norway 0.1 FW
Saskatch ewa n 0.7–10.6 F W
Can ada (no r mal) 0.1 FW
Can ada (poll u ted) 0.5–0.7 F W
Lake St. Clair 2.0–3.0 F W
NW O n tari o mining a r ea 5.6 FW
Wisco n si n 0.9–1.4 F W Manitoba, ma nmade re serv oir Preimpo und ment (19 71– 73) 0.25–0.3 5 FW Bodaly Postimpo und ment (19 79– 82) 0.67–0.9 5 FW et al. 1985
Fish
M u s c l e F r es hw a t e r Total Hg 0.27–1.7 F W Cap pon a nd Methyl Hg Max. 1.4 FW Smith 1982
M a r i n e Total Hg 0.11–5.7 F W
M e t h y l H g M a x

. 4

. 5 F W

Laho ntan Re servoi r, Neva da, 1981

Muscle, 5 sp p. Max. 2.3–3.9 FW Coo per 1 983

Liver, 5 spp. Max. 2.4–8.3 FW
Hea r t, 4 spp. Max. 1.1–2.1 FW
Loui siana, Atchafal aya Riv e r, 1981

Whol e, 8 spp. 0.06–0.7 9 FW Wing er an d Andre a sen 19 8 5
Nation wide, USA, whole
1969 –70 0.26 (0.05 –1. 7) FW Hen derso n a nd

Pacific Coa s t and Alaska 0.25 (0.05 –1. 7) FW Shanks 19 73
Southwe s t 0.08 (<0.05– 0.14) F W



### 20North Cent ral 0.20 (<0.05– 0.05) F W
North e a s t 0.23 (<0.05– 0.08) F W
Southea st 0.23 (<0.05– 1.0) FW
1972 0.15 FW
1976 –77 0.11 FW Lowe et al.
1978 –79 0.11 (0.01 –1. 1) FW 1985
1980 –81 0.11 (0.01 –0. 77) F W
Thailand
M u s c l e Nea r chl o ralkali plant
No w a st e wat e r sy st em, 1975 –76 0.32–3.6 F W Suckcha r o e n With wa ste water sy stem, and Lo deniu s 1978 0.1–1.4 F W 1980
Control location 0.01–0.3 F W
V a riou s s p e c i e s M u s c l e From u npollut ed are a s 0.04–0.1 5 FW NAS 1978
From mo dera t ely Hg-poll u ted

areas >1.0 F W From hig h ly polluted area s 10.0–2 4.0 FW
B l ackf i s h, Ga dop sis m a rm oratu s M u s c l e From Hg-co n taminated
sediment s Max. 0.64 FW Bycroft
From u n co ntaminated sed i ments Max. 0.06 FW et al. 1982
Cha nnel catfish, Ictalu ru s pun ctatus
M u s c l e Lake Erie 0.3–1.8 F W Jen k in s 19 80
Lake St. Clair 0.5–2.0 F W
Ohio 0.1–0.4 F W
Illinois 0.03–0.2 F W Oreg on 0.02–1.5 F W Georgia 0.1–1.9 F W
Texas 0.2–2.5 F W
Pumkin se ed, Lepom is gib b o su s 16 lakes, Ont a rio, Ca nad a, 1981

Muscle 0.09–0.5 4 FW Wren and M a cCrimmo n 19 84
B l ack m a rlin, Makai r a in dica
M u s c l e Pacific O c ea n 0.6–4.3 Cap pon a nd
NE Australia 0.5–16.5 F W Smith 1982

Blue marlin, Makai r a ni gri can s



### 21M u s c l e Ha waii 0.4–14.0 F W
Total Hg 0.4–0.9 F W Methyl Hg Max. 0.16 FW Larg e mo uth bass,

Micropte r u s salm oide s M u s c l e Texas 0.1 FW Jen k in s 19 80
Utah 0.3–7.3 F W
California 0.1–0.6 F W Oreg on 0.2–1.8 F W
Wa shin gton 0.1–0.3 F W Georgia 0.1–5.4 F W Michig an 0.2–0.9 F W
Illinois 0.03–1.2 F W
Ar iz on a 0

. 3 F W Striped ba ss, Morone saxatilis
Laho ntan Re servoi r, Neva da,
1981 Single sp eci m en, 16 years old
Muscle 9.5 FW Coo per 1 983
H e a r t 5

. 6 F W
Liver 23.7 FW
M u s c l e Body weight
<3.2 kg <0.5 F W Alexande r 3.2–5.7 kg 0.5 FW et al. 1973

> 5 .7 kg > 0 .5 FW
Yellow pe rch, Pe r ca

flav esc e ns Whol e Age 0 0.07 FW Busch 198 3 Age I 0.13 FW Age II 0.22 FW
Rou nd whitefish,

Prosopium cylind r a c eum Sagina w Bay, Michiga n 1977 –78
Fillets Methyl Hg Max. 0.05 FW Miller and
Total Hg Max. 0.1 FW Jud e 198 4 Trout, Salmo spp. M i s s o u r i
Liver and m u scl e



### 221946 –50 3.0 FW Lloyd
1973 0.1–0.3 F W et al. 1977
Brook trout, Salveli n u s fontinalis
A d iron da ck la ke s (15 )

, Ne w Y o r k

Whol e <1.0 F W Sloan and S c hofield 19 83
Lake trout, Salveli n u s nam aycu sh
M u s c l e British Colum b ia 1.1–10.5 F W Jen k in s 19 80
Ontario 0.3–1.3 F W Queb ec 0.3–1.2 F W
Ne w York 0.3–0.6 F W

Sharks, Au stralia, 1980 Muscle, 7 sp p. Ca rc h a r h inus sp p. Max. 4.3 FW Lyle 1984 Sphyrn asp p. Max. 4.9 FW Walleye,

Stizostedion vitreum vitre u m Manitoba, ma nmade re serv oir
M u s c l e Preimpo und ment (19 71– 77) 0.2–0.3 F W Bodaly Postimpo und ment et al. 1984 (197 8–9 2) 0.6–0.8 F W

Tuna s, 1981, 5 spp.
Muscle 1.0–6.3 F W Schreibe r 19 83 Swordfish, Xiphia s gladiu s M u s c l e NW Atlanti c 2.0 FW; 8.1 DW Jen k in s 19 80
Peru 1.1–1.8 F W
Pacific 0.5–1.7 F W
W. Atlantic 0.05–4.9 F W
Gibralte r Stra it 1.0–2.0 F W Amphibians and Re ptiles Europ ean toa d

, Bufo bufo Yugosl a via
Control area Liver 1.5 FW Kidney 1.2 FW Lung 0.2 FW
M u s c l e 0

. 2 F W Egg 0.06 FW
Polluted mercury mining a r ea Liver 21.8–2 5.5 FW Jen k in s 19 80 ; Kidney 22.8–2 4.0 FW Terhivu o et al. 1985



### 23Lung 1.7 FW Muscle 2.3–2.9 F W Egg 2.3 FW Logg erh ead sea turtle,

Caretta caretta Egg 0.01 FW Hall 19 80
C r oc od ile

, Croco d ylus a c ut us Egg 0.7 FW Bullfrog, Ra n a cate sbei an a Lake St. Clair
Carca ss 0.1 FW Jen k in s 19 80
Liver 0.3 FW

Leopa rd fro g , Rana pipi en s Lake St. Clair
Carca ss 0.1–0.2 F W
Liver 0.5–1.1 F W
Florid a Liver 0.1 FW Frog, Rana te m poraria Yugosl a via, 1975
From Hg-mini ng are a Liver 21.0 FW Terhivu o Kidney 16.2 FW et al. 1984
M u s c l e 3

. 4 F W Egg 1.3 FW
From u n co ntaminated a r e a A l l t i s s u e s < 0

. 0 8 F W
Birds
Gosha w k, Accipiter gentilis
Swede n Feathe r 1860 –194 6 2.2 FW Jen k in s 19 80
1947 –65 29.0 FW
1967 –69 3.1–5.1 F W
Finnish sp arrowh awk,

A ccipit e r ni s u s Feathe r Finland
1899 –196 0 4.1 (2.1–7.7 ) DW Solonen a n d
1961 –70 11.1 (2.3– 42. 0) DW Lode niu s 198 4
1971 –82 7.4 (1.0–2 9.0 ) DW
G e r m a n y 1972 –73 4.9 (0.4–2 0.3 ) DW



### 24N o rw a y 1976 2.0–20.0 DW
Woo d du ck, A i x spo n s a Tenne ssee, 1 972– 73
Juv enil e s Liver 0.4 (0.1–1.1 ) FW Lind say and
Muscle 0.1 (0.05– 0.4 ) FW Dimmi ck 19 8 3
Fat 0.1 (0.01– 0.4 )
A d u l t s Liver 0.2 (0.1–0.3 ) FW
Muscle 0.08 (0.06 –0. 11) F W
Fat 0.06 (0.01 –0. 11) F W Blue-winge d teal, Anas di scors M u s c l e Lake St. Clair 0.1–2.3 F W Jen k in s 19 80
Ontario 3.8–10.4 F W
Wisco n si n 0.0–0.5 F W
Illinois 0.05 FW
Great blu e he ron, Arde a he rodiu s L i v e r Lake St. Clair 97.0 (14.6

– 1 75.0) F W
Ne w Brun swi c k 4.5 FW
Lake Erie 0.7–4.3 F W
Wisco n si n 0.5 (0.2–1.1 ) FW
Birds
Antarc tic
L i v e r 1977 –79
4 spp. 0.5–1.3 F W Norheim
3 spp. 2.7–2.9 F W et al. 1982
1980
5 spp. 0.5–2.1 F W Norheim a n d
K

j o s

- H a n s s e n 1984 Belgium, 197 0–81 Liver, 30 sp p. Aquatic bi rd s 0.11–3 5.0 FW Delb eke
Terrest r ial birds ND-14.0 F W et al. 1984
Ha waiian, 19 80 Egg, 3 spp. 0.12–0.3 6 FW Ohlen dorf an d
H a r r i s o n 1 9 8 6
North Ame r i c a Feathe r



### 25F r o m a r e a s w i t h

mercu r y-tre a ted se ed dre ssi ng Seed-eating son gbirds 1.6 DW NAS 1978 Upla nd gam e birds 1.9 DW
From u n treat ed are a s Seed-eating son gbirds 0.03 DW Upla nd gam e birds 0.35 DW
North w e s te rn Ontario, Can ada
From a h eavily mercu r y- contaminate d fresh w ate r system
L i v e r Scaveng ers 57.0 (13.8

– 1 21) F W Fimreite 19 79
Fish eate r s 39.5 (1.7– 9 1 ) FW
Omnivores 26.6 (9.5– 5 3 ) FW
Invertebrate feede rs 12.4 (3.2– 2 8 ) FW Vegetari a n s 6.2 (1.9–2 8) FW Diving du cks Max. 175.0 NAS 1978
M u s c l e Diving du cks Max. 23.0 FW
M a l l a r d

, Anas platyrh y

n c h o s Max. 6.1 FW Eagle-owl, Bubo bubo
Swede n, 196 3–76
Feathe r Inland po pula t ions 3.2 DW Broo an d
Coa s tal po pul ations 6.5 DW Odsj o 198 1
1829 –193 3 0.3–3.6 F W Jen k in s 19 80
1964 –65 12.8–4 1.0 FW Pereg r ine, Fa lco pe reg r inu s Feathe r 1834 –184 9 2.5 DW NAS 1978
1941 –65 >40.0 DW
Swedi sh gyrf alco n, Falco rusticolus
Ne stling s , feather Percent aqu a t ic bird s in die t
Non e 0.035 F W Lindb erg 1 9 8 4
4.8% bioma ss 0.66 FW
10.6% bioma s s 1.22 FW

American bal d eagle,
Haliaeetu s l

eucoceph alu s Egg
Maine (highe st con c e n trati ons Nationwi de)
1974 0.35–0.5 8 FW Wiemeye r



### 261975 0.22–0.6 3 FW et al. 1984
1976 0.22–0.6 6 FW
1977 0.28–0.9 0 FW
1978 0.30 FW
1979 0.84–1.2 F W

Ring ed he rrin g gull,
Larus arg e n t atus
Denm ark, 19 75–7 6
Liver 0.65 (0.08 –2. 34) F W Karlog a nd
Clau se n 198 3
O n t a r i o Egg 1.5–15.8 F W Jen k in s 19 80
Albumin 16.1–2 2.7 FW
Yolk 3.4–3.5 F W
California sea gull,

Larus califo r nicu s Laho ntan Re servoi r, Neva da, 1981
Muscle 0.4 FW Coo per 1 983
Liver 1.0 FW Egg 0.1–0.2 F W Osp r ey, Pand ion haliaetu s Swede n Feathe r 1840 –194 0 3.5–5.0 F W Jen k in s 19 80
1940 –66 >17.0 F W
Brown peli c a n ,

Pelecanu s o cci dentali s Egg
South Ca rolin a 0.3–0.5 F W
Florid a 0.4 FW
California 0.4 FW
Liver 0.75 DW Ohlen dorf Kidney 0.68 DW et al. 1985
Feathe r 0.97 DW Ring -ne c ked phea sa nt,

Phasianu s colchi cu s M u s c l e Denm ark 0.01 FW Jen k in s 19 80
Idaho 0.0–15.0 F W
Indiana 0.06 FW Oreg on <0.5 F W Wyoming 0.2–0.6 F W
Colo rad o 0.04–0.6 F W



### 27Utah 0.15 (0.01 –2. 1) FW
California 1.6–4.7 F W
Wisco n si n 0.01–0.0 8 FW
Illinois 0.02–0.0 3 FW
Great cre s ted grebe,

Podic e ps cris tata Swede n Feathe r 1865 –194 0 <10.0 F W
1940 –66 >14.0 F W Mourning d o ve, Zenaida m a crou ra L i v e r Eastern Unite d States 0.07–0.6 7 FW
Mammal s

Australi an fur seal,
Arctoce phalus pu sillu s Muscle 0.9 (0.1–1.9 ) FW Bache r 19 85
Liver 62.3 (1.0– 1 7 0 .0) FW Kidney 0.6 (0.1–1.7 ) FW Spleen 1.3 (0.0–3.8 ) FW
Brain 0.7 (0.0–2.5 ) FW
Hair 9.6 (1.1–1 9.8 ) DW
W o od mo us e , Apodem us sylvaticu s Great Britain
In field with Hg-tre ated

w h ea t s e ed
Liver Max. 7.1 FW Jen k in s 19 80 Kidney Max. 11.7 FW
In chloralkali area Liver Max. 0.5 FW Kidney Max. 1.3 FW
Control area Liver Max. 0.07 FW Kidney Max. 0.3 FW
Roe d eer, Capreolus cap r e o lus Males, Pola n d

, 1977– 78
From Hg-co n taminated h a b i tat
Muscle 0.047 F W Krynski
Liver 0.036 F W et al. 1982 Kidney 0.053 F W
From u n co ntaminated a r e a Muscle 0.013 F W
Liver 0.015 F W



### 28Kidney 0.027 F W Beaver, Ca st or ca nad en si s Wisco n si n, 1972– 75
All tissue s <0.09 F W Sheffy and
St. Amant 1982 Cat, Felis dom e sticus
Ate fish from belo w chl o ral k ali plant, NW Ontario
Brain 6.9–16.4 F W Jen k in s 19 80
Pancrea s 4.3–4.9 F W Kidney 0.8–13.4 F W
Liver 14.2–6 7.1 FW
Fur 121.0– 392.0 FW
Riv e r otter, L u tra ca nad en sis
Winni peg River, Manitoba, Ca nada, 19 79– 8 1
M a l e s Liver Max. 8.9 FW Kuce ra 19 83 Kidney Max. 6.5 FW
Brain Max. 3.1 FW
F e m a l e s Liver Max. 3.9 FW Kidney Max. 1.8 FW
Brain Max. 0.6 FW
Wisco n si n, 1972– 75
Brain 0.7 FW Sheffy and
Muscle 1.4 FW St. Amant 1982
Liver 3.3 (Max. 23.6) FW Kidney 8.5 (Max. 20.9) FW
F u r Industri a l are a 9.5 (Max. 63.2) FW
Noni ndu strial area 3.8 FW Bobcat, Ly n

x

r

u fu s H a i r Georgia USA Upp e r coa s ta l plain 13.1 DW Jen k in s 19 80
Lower coa s ta l plain 0.9 DW Mink, Mu stel a visi on Wisco n si n, 1972– 75
Brain 0.5 FW Sheffy and
Muscle 1.3 FW St. Amant 1982
Liver 2.1 (Max. 17.4) FW Kidney 2.3 (Max. 12.5) FW



### 29F u r Industri a l are a 10.5 (Max. 41 .2) FW
Noni ndu strial area 3.0 FW
Winni peg River, Manitoba, Ca nada, 19 79– 8 1
M a l e s Liver Max. 9.9 FW Kuce ra 19 83 Kidney Max. 6.4 FW
Brain Max. 2.4 FW
F e m a l e s Liver Max. 10.7 FW Kidney Max. 8.1 FW
Brain Max. 2.1 FW
Musk rat, O n da tr a

z

i be th icus
Wisco n si n, 1972– 75
All tissue s <0.06 F W Sheffy and
St. Amant 1982 Sheep, Ovis aries
Gra z ing fo r 2 3 months o n Hg-co n tamin a ted field
Diet (g ra ss )
Winter 6.5 DW Edwa rd s and
Summer 1.9 DW Pumphe ry 19 82 Lung Max. 4.0 FW Kidney Max. 3.1 FW
Liver Max. 2.4 FW
Brain Max. 1.1 FW
F l e s h < 1

. 0 F W
Harbor s e al,

Phoca vituli na richa r di
L i v e r California 269.0 (8 1.0– 700.0) F W Jen k in s 19 80 Oreg on 0.3–68.0 F W
Wa shin gton 1.3–60.0 F W
Pribilof Islan d s 0.6–8.9 F W
Ra ccoon, Pro c yon lotor
Wisco n si n, 1972– 75
Brain <0.02 F W Sheffy and
Muscle 0.08 FW St. Amant 1982 Kidney 1.4 FW
Liver 2.0 FW
Fur 3.8 FW Gray squirrel, S c iuru s ca rol i nen sis



### 30Hair, Flo r ida, 1974
Rural area s 0.43 FW Jen k in s 19 80
U r b a n Age 0–1 1.0 (0.07– 6.7 ) FW Age >2 2.7 (0.30– 9.2 ) FW Striped dol phi n,

Stenella coe r uleo alba Adults, Jap a n , 1977–8 0
M u s c l e Total Hg 15.2 FW Itano Methyl Hg 5.3 FW et al. 1984a
L i v e r Total Hg 205.0 F W
M e t h y l H g 7

. 0 F W Kidney
Total Hg 14.7 FW
M e t h y l H g 3

. 2 F W
Whol e body Age 1 year Total Hg 0.8 FW Itano Methyl Hg 0.4 FW et al. 1984b Age 3 years T o t a l H g 1

. 8 F W
M e t h y l H g 1

. 0 F W Age 4 years T o t a l H g 3

. 0 F W
M e t h y l H g 1

. 5 F W Age 14 years T o t a l H g 4

. 5 F W
M e t h y l H g 2

. 6 F W Age 20 years Total Hg 10.7 FW
M e t h y l H g 3

. 5 F W
Red fox, Vulpes vulpe s H a i r Georgia, US A Upp e r coa s ta l plain 2.3 DW Jen k in s 19 80
Lower coa s ta l plain 0.5 DW
Wisco n si n, 1972– 75
Fur 0.6 FW Sheffy and
Other tissu e s <0.14 F W St. Amant 1982

California sea lion, Zalophu s ca lifornian us



### 31L i v e r Mother 73.0–1,0 26.0 DW Jen k in s 19 80 Pup 0.9–16.0 DW Kidney
Mother 4.1–43.2 DW
P u p 0.6–6.7 DW

a Con c e n trati ons a r e liste d as m ean, ran ge, or maxim u m (Max.).
b Each refere nce a pplie s to the value in the same ro w and in the rows that follow for which n o other refere nce i s indicated.

Nation wide m onitorin g of whole fish d u ri ng the peri od 1969 to 19 81 demon strated that the highest Hg

con c e n tration s (0.33 to 1.7 mg/kg F W) were in no rthe rn squ a wfi s h ( Pty c h oc he ilus ore gon en si s) from the Colum b ia Riv e r ba sin in th e Pacific Nort hwe s t (Hend er son an d Sh anks 19 73; L o we et al. 19 85). Elevated Hg

con c e n tration s in this pi sci vorou s sp eci e s were attri b ut ed prim arilyto the presen ce of majo r ci nnab ar de po sits and with Hg u s e a s soci ated with mineral mining in t he Colum b ia Riv e r ba sin. No rt hern squ a wfi s h may have a natural ten d e n cy to accum u late high co nce n tration s of mercury in their flesh

- -as is well kno w n for olde r spe c ime n s oflong-lived p r edatory fish e s su ch a s tun a s, billfish e s, bluefish ( Po ma to mu s salt at

rix ), strip ed b a s s ( Morone saxatilis), north ern pike ( Es ox lucius), and m a ny spe c ie s of sha r ks--b ut Hg uptake kin e t ics in squa wf ish requi re s furth e r re se arch (Lowe et al. 1985).
Of 159 sp eci e s of finfish a nd sh arks fro m the coa s tal waters of Alaska, Ha waii, and the conte r mino us Unit ed States, mercury con c e n tra t ions in mu scl e were usuall y less than 0. 3 mg/kg fre s h weight (Hall et al. 1978). Mean Hg con c entra tions in excess of 0.5 mg/kg fresh we ig h t muscl e we re recorded in 31 sp eci e s, in cludi ng 10 spe c ie s of sh arks an d 4 sp ecie s of billfishes; ho weve r, these 31 sp ecie s a c count ed for less th an 0.65% of the catch intend e d for huma n consumption (Hall et al. 197 8).

In birds, it is gene rally acknowl edge d th at mercury co nce n tration s are hig h e s t in spe c ie s that eat fish and other bi rd s. Resid u e s we re highe st in kid ney and liver, but total Hg conte n ts were signifi cantlymodified by food prefe r en ce a nd availability, and by migratory pattern s (N AS 1978; Delb eke et al. 1984). Also, there is a n in verse relation shi p b e twee n total Hg an d perce nt methylmercur y in tissue s of variou s a v ian spe c ie s (Norheim et al

. 1982; Karl og and Cl au sen 1983 )--a patt e rn that seem s to hold for a ll vertebrate o r gani sm s for whi c h data a r e available. Die t and migratio n are the mo st important Hg m odifiers in birds. Fo r ex ample, the hi gher level s ofHg in juvenile tha n in adult wo od du cks ( Aix spon sa ) from Tenne ssee were rel a ted to dietary pattern s: juvenile s prefe rre d insects, whe r ea s adult s prefe rre d pon dwee d tubers; Hg resid u e s we re higher in the inse cts tha n in the pond we eds (Lind s ay and Dimmi ck 1 9 8 3 ). Con c ent rations of Hg in livers of Antarcti c birds re flected Hg bo dy burd e n s accu mulated du rin g migratio n, while the bi rd s we re ove r wi ntering n e a rindu striali z ed area s. Con c e n tratio ns were hi gh est in sp eci e s that ate higher tr op hic lev e ls of prey an d were espe cially prono un ced for sk ua s, Catharac ta spp.; ho wever, signifi cant inh e re nt interspe cie s differen c e s were evide n t (Norheim et al

. 1982; Norh ei m and Kjos-Hansse n 198 4).
The sig n ifica n ce of Hg re sidue s in bird s is not fully understood. Fo r example, all egg s of the Ameri c an b a ld eagle ( Hali ae etus leu c o c e phalu s) colle cted Nation wid e contai ned d e tectabl e levels of Hg, butthe mean wa s 0.15 mg Hg/ k g (fre sh weig ht basi s ) in e ggs fro m un su cce ssful n e sts vs. 0.11 in egg s from su ccessful ne st s (Wie m eyer etal. 1984). Ma ny other co ntaminant s--e spec i a lly orga nochlori ne co mpoun ds--we re in eagl e eg gs, and several were present at levels that potentially interf ere with ea gle rep r o d u c tion (Wiemeye r et al. 1984). It is not now p o ssi b le to implicat e Hg a s a majo r ca use of unsu c ce ssful e agle re produ ction.

Bird feathers have bee n used for some time as indi ca t o rs of Hg loadings in terre s trial an d marine environ ment s. The keratin in bird feathe rs is not ea silydegra dabl e, and Hg is pro bably asso cia t ed firmly with the disul phide b o nds of keratin

. Consequ ent ly, it has bee n pos sibl e to comp are Hg conte n ts of feathers re ce ntly sampl ed with those from m u se um birds, thereby e s tab lis hin g a time seri es (Apple quist et al. 19 84). The m o st prob able sou r ce of re cent e l evated Hg re sidu es in feat hers of the Finnish sp arro wha w k ( A c cip i t e r nisu s) wa s from co nsum ption of avian granivo re s that had be com e contami nat ed as a result of eating see d s treat ed wit h



### 32orga nom ercu ry comp oun d s ; in 1981, 5. 6 tons of met hoxyethylmercury comp ou nds were use d in Finnish agri c ultu re for protectio n of see d s a gain s t fungi (Solon en and L ode n i us 19 84). Ca ptive Swedish eagle

- o w ls ( Bubo b ubo), with low Hg content in feather s (<1.0 m g /kg DW), that were intr odu ced into coa s tal area s qui ckly reflecte d the high (6.5 m g /kg) Hg level s in feathers of w ild ea gle-owls from that re gion. Ca ptive bird s rel e a s e d into inland territorie s, wh ere Hg level s were ne ar b a ckgrou nd, did n o t accumulat e Hg in feath e rs (Bro o and Odsj o 198 1). Mercury level s in feathers of nestling S w edi sh gyrfal con s ( F a lco rusticolus) sho w ed a b e tter correl ation wi th Hg levels i n actual foo d items than wit h levels ba se d on adult fea t hers. Me rcury concentrati ons in feathers were hig h e rin nestlin gs fed partly with aq uat ic bird sp e c ie s co ntainin g >0.07 mg Hg/kg in pe ctoral muscle than i n nestlin gs fe d willo w gro u s e ( L ago pu s lagop us) and ptarmig an ( L agop us m u tus), both of wh ich contai ned <0. 01 mg Hg/ k g in pecto ral m u scle (Li ndb e r g 198 4). In some insta n ce s there wa s a sub s tantial time lag, up to 10 years, bet we en the introd u c tion of a pe stic ide, su ch a s alkylme r cury, its subse q u ent banni ng, and measurable d e clin es of Hg in feathers of several sp eci e s of Swedi sh rapto r s; this was the ca se for variou s spe c ie s of Fa lco, Hali aeetu s , Bubo, Buteo , and Acc i piter (Wallin 1984). Accordingly, a reduction in Hg cont ent in feathers of free-livin g birds may be su ffi cient to establish an imp r oved situ atio n.
Among mam m als, ma rine pinnip eds u s ually contai ne d the highe st repo rted con c entration s of Hg in tissue s (Tabl e 6). Th e relatively high co ncentrat i ons a ppe are d to be a re su lt of natural proce s se s rath er than of anthro pog eni c activities, h o weve r, and prob ably did not rep r e s enta significant risk to pinnip ed health. In gene ral, Hg concentratio n s incre a sed si gnifica ntly with increa sing age of t he organi sm, as shown (Fig ure 2) in the livers of h a rbo rseal ( P hoca gro enla ndica ), grey seal ( H a lichoe rus g r ypu s), California sea lion ( Zalo phu s californian us), and northe r n fur se al ( Callorhinus ursinus). The me cha n ism s to accou n t for this phe nome n on in pinnip eds a r e similar to tho s e re po rted b yIt ano et al. ( 1984 a,b, c) for the stri ped dolphi n ( Sten ella

coe r ule oalb a ). They sho w e d that tissue con c e n tration s of me rcu r y in stripe d dolp h ins in crea se d with increa sing age of the ani mal, rea c hin g a plateau in 20 to 25 years; we re high e s t in liver, although mu scle accou n ted for about 90% ofthe total body Hg burd en; were present in the methylated form in fetal and suckl i ng stag es, b u t the prop ortio n of methylmercu ry decre ased over time wit h no ab solute incre a se after age 10 yea r s; we re excre t ed slo w ly by all developm ent al stage s, an d slo w e s t in older dol phin s (re sultin g in h i gher a c cum u lations); and were correl ated strongly with sel enium con c e n tration s in al l age gro u p s . It is probabl e that inorga nic Hg and sele nium

were co mple xed in a 1:1 molar ratio, in a form biolog ically unavail able to mari n e mammal s (and proba bly other mammal s ), th ereby si gnificantly decrea s ing the risk ofme rcury toxico sis to indivi dual s with grossly elevate d Hg body burden s (Eisler 1 984, 1985). La rg e coloni es of pi nnipe ds a nd, to a lesser ex tent, marine b i rds al ong the

we stern coa s t of the United States may make Hg avai lable to mussels ( M ytilus californianus) t h rou gh fec a l elimination oflarge am ount s of Hg, re sul t ing in abno rmally high Hg levels in mussel s from several west coa s t sites (Fleg a l et al. 1981).
Among furb e a re rs in the Wisco n si n Ri ver drai nag e syst em, Hg b u rde n s we re highe r in fish -eating than in herbivo ro us speci e s--i.e., ri ver otter ( L u tra can ade nsi s) > min k( Mu stela vison ) > raccoo n ( Pro c yon loto r ) > red fox ( Vulpes fu lva ) > mu sk ra t ( Ondatra z i be th ic us) > be aver ( Ca stor can ade nsi s) (Sheffy and St. Amant 1982 ). In gene ral, fur containe d the highe st Hg le vels, followe d by liv er, kidney, muscle, a nd brai n, in that orde r (Ta b l e 6; Sheffy and St. Amant 1982 ). Mercury lev e ls in pi scivo rous furbea re rs coll ecte d from the Wi sco n sin River ba sin parall e led Hg levels in fish, crayfish, and bottom sedi ment s from that s y s t em; levels in all compartments were highe st abo ut 30 km do wn strea m from an are a that s uppo rted 16 pulp an d pap er mills a nd a chloralkali pl ant (Sheffy and St. Amant 1982). Mink a nd river otter accumulated a b o u t 10X more Hg than di d p r edato r y fishe s from the sa m e drain age a r eas--su gge sti ng that these furbea re rs ca n serve a s se nsitive indi cat o rs of me rcury, even at very low level s of Hg contamin ation (Ku c era 1983).

Dome st ic she ep ( Ov is

sp.) allowed to graze for 23 mo nths on g r a s s contamin ate d with Hg (up to 6.5 mg/kg dry weig ht) caused by atmosp heri c emi ssi on s of a nearby chlo ral k ali site, retai ned ab out 0.1 % of the total Hg taken in by in gestio n and i nhalatio n, althoug h re sidu es in flesh we re negli g ible (Edwa r d s and Pumphe ry 19 82). It was co ncl u ded that co ntamination of gra ss a s a re sult of atmospheri c di scha rge s of inorga nic He from

chlo ral k ali sit e s cau s e s no haza r d, eithe rdire ctly to gr azin g animal s or indirectly to human s wh o might ultimately

con s um e thei r flesh.



### 33A C U T E AND C H R O N I C TOXIC I TY
GENERAL For all organi sm s tested, e a rly develop mental sta g e s we re the m o st se nsitive, and organ om ercury comp oun ds--esp e ci ally methylmercury--were more toxic than inorg anic forms. Numerou s biol ogical and a b iotic factors modif ythe toxicity of Hg co mpo und s, someti mes by an o r der of mag n itude or m o re, but the mech anism s of action are not clea r.

Lethal con c e n tration s of total Hg to sen s itive, r epre s e n tative organi sm s varied from 0.1 to 2.0 ug/l of medium for a quatic fau na; from 2.2 to 31.0 mg/kg bo dy weight (a cute oral ) and 4.0 to 40.0 mg/kg (di e tary) for bird s; and fro m 0.1 to 0.5 mg/kg bo dy weig ht (daily dose) an d 1.0 to 5.0 mg/kg (dieta ry) for mammal s

. AQ UATI C O R G ANISMS

Toxic concen trations of me rcu r y salt s ra nged fro m less than 0.1 ug/ l to more than 200 ug/l for repre s e n tative spe c ie s of marine a nd fre s hwate rorgani sm s (Ta b le 7). The lowe r concentratio n s of <2.0 ug/l reco rde d we re
usu a lly asso ciated with ea rly developme n tal stage s, long expo su re s, and flowth rough te sts (T able 7). Amo ng metals te sted , mercu r y wa s the mo st toxic to aquatic orga nisms, a nd org ano me rcu r y co mpou nds sho w e d the greate s t bio c i dal potential (Eisler 1 981 ). In general, toxici ty was hig her at elevate d temperatures (A rmst ron g 1979 ), at red u ce d sali nities in mari ne organi sms (McK enney and Co stlow 1 981 ), and in the p r esen ce of other metals such as zi nc a nd le ad (Parke r 19 79).
Signs of acute mercury poi soni ng in fish inclu ded flar i ng of gill cove rs, in cre a sed freque ncy of respi r ato r y movement s, loss of equilib rium, and slu ggishne ss (A rmstro ng 19 79 ). Signs of ch roni c mercu r ypoiso ning inclu ded em a c iation (due t o appetite lo ss), brain le sio n s, cata ra cts, diminish ed resp on se to chang e in light intensity, inab ility to capture food, abno rmal motor co or din a tion, an d variou s erra ti c behavio rs (Arm stro ng 1 979; Ha wryshyn et al. 1982). Me rcu r y re sidu e s in seve rely poi sone d fish that died soo n thereafte r range d (in mg/ k g fresh weig ht) from 26 to 68 in liver, 16 to 20 in br ain, a nd 5 to 7 in whole bo dy (Armstro ng 19 79 ).

Table 7. Toxicities of ino r g anic a nd orga nic me rcury co mpou nd s to sele cted spe c ies of aqu atic organi sm s.

Chemi c al spe c ie s, eco s yst e m, taxonomi c Con c e n tratio n grou p, spe c ie s, and othe r variabl es Effect a (μg Hg/L m e d i um) Referen c e

Inorganic M e rcur y F r es hw a t e r C r us tac e an s Crayfish, Orcone ctes lim osus LC-50 (30 d) 2.0 EPA 1980
Clad ocera n , Dap hnia m a gn a LC-50 (96 h) 5.0 EPA 1980
Clad ocera n , Dap hnia m a gn a LC-50 (LT) 1.3–1.8 EPA 1980
S c u d

, Gam m a ru s pseud oli

m naeus LC-50 (96 h) 10.0 EPA 1980
F i s h
Rainbow trout, Salm o gairdneri
Juvenil e s LC-50 (96 h) 155.0–200.0 EPA 1980
E m b r y o

- l a rv a Static test LC-50 (28 d) 4.7 Birge et al. 1979
Flowth rou gh test LC-50 (28 d) <0.1 Birge et al. 1979
Cha nnel catfish, Ictalu ru s pun ctatus
E m b r y o

- l a rv a



### 34Static test LC-50 (10 d) 30.0 Birge et al. 1979
Flowth rou gh test LC-50 (10 d) 0.3 Birge et al. 1979 Larg e mo uth bass, Micropt eru s salm oid e s E m b r y o

- l a rv a Static test LC-50 (8 d) 140.0 Birge et al. 1979
Flowth rou gh test LC-50 (8 d) 5.3 Birge et al. 1979
Brook trout, Salveli n u s fontinalis LC-50 (LT) 0.3–0.9 EPA 1980
F i s h

, Notopte r us n o topte r u s LC-50 (96 h) 440.0 Verma an d T onk 1 983 Amphibia n s Narro w -mout hed toad,
Gast ro

phr yn e car o line n si s Embryo-l arva LC-50 (96 h) 1.3 Birge et al. 1979
T r e e f r o g s , Hyla spp. Embryo-l arva , 5 spp. LC- 50 (96 h) 2.4–2.8 Birge et al. 1979 Leop ard frog, Rana pi pien s Embryo-l arva LC-50 (96 h) 7.3 Birge et al. 1979
Cric ket frog, Ac ris s p

. Embryo-l arva LC-50 (96 h) 10.4 Birge et al. 1979
Anura n s, 4 spp. Embryo-l arva LC-50 (96 h) 36.8–6 7.2 Birge et al. 1979
Marbl ed sala mande r, Am bystom a opa cum Embryo-l arva LC-50 (96 h) 107.5 Birge et al. 1979
Marine
Protozoan s Ciliate, Urone m a m a rinum LC-50 (24 h) 6.0 Parker 19 79
Molluscs
Softs hell c l am, Mya arena ria LC-50 (168 h ) 4.0 Eisler a nd
Hen n e k ey 19 7
H a r d s h e l l c l a m , Mercena ri a m e rcen aria
Larva LC-50 (48 h) 4.8 EPA 1980
Larva LC-5 (9 d) 4.0 EPA 1980
American oyster, Cra s so st r ea vir g ini ca Embryo LC-5 (12 d) 3.3 EPA 1980
Larva LC-50 (48 h) 5.6 EPA 1980
Adults LC-50 (48 h) 5.5–10.2 EPA 1980
Blue mussel, Mytilus eduli s LC-50 (96 h) 5.8 EPA 1985 Slipper limp e t, Crepid u la fo rnicata
Larva LC-50 (96 h) 60.0 Thain 19 84
Adults LC-50 (96 h) 330.0 Thain 19 84
B a y s c a l l o p , Argop ecte n irradia n s Juvenil e s LC-50 (96 h) 89.0 Nel s on
et al. 1976
C r us tac e an s



### 35Fiddle r crab, Uca pugil a tor
Zoea LC-50 (8 d) 1.8 EPA 1980 My sid sh rimp

, Mysid opsi s

bahia
Juvenil e s LC-50 (96 h) 3.5 Gentile et al. 1983 Egg to egg LC-50 (LT) 1.8 Gentile et al. 1983
Dun gen ess crab, Ca ncer m agister
Larva LC-50 (96 h) 6.6 Glickstei n 19 78 Cop epo d, Acartia tonsa , adult LC-50 (96 h) 10.0–15.0 EPA 1980 Prawn, Pena eus in dicus
Postlarva LC-50 (48 h) 16.1 McCl urg 198 4
Postlarva LC-50 (96 h) 15.3 McCl urg 198 4
Annelid s Polychaete, Capitell a capitata
Larva LC-50 (96 h) 14.0 EPA 1980
F i s h
H a d d o c k

, Mel anog ram m u s aeglifinu s Larvae LC-50 (96 h) 98.0 EPA 1980 Organic Me r c ur y F r es hw a t e r Planari a n s F l a t w o r m , Du gesi a

dorotocephal a Adult LC-0 (1 0 d) 200.0 Best et al. 1981
Adult LC-100 (5 d) 500.0 Best et al. 1981
C r us tac e an s Clad ocera n , Dap hnia m a gn a LC-50 (LT) 0.9–3.2 EPA 1980
F i s h
Rain bo w trou t
Larva LC-50 (96 h) 24.0 EPA 1980
Juvenil e LC-50 (96 h) 5.0–42.0 EPA 1980
Broo k trout Yearling LC-50 (96 h) 65.0 EPA 1980
Marine
C r us tac e an s Amphipo d, Gam m a rus due beni LC-50 (96 h) 150.0 EPA 1980

a Abbreviation s: LT = lifetime exposure; h = hou rs; d = days.

BIR D S Signs of mercury poisonin g in birds in clu ded mu scula r incoo r din a tio n , falling, slo w ne ss, fluffed feathers, calmn e ss, wit hdra w al, hyp o rea c tivity, hypoa ctivity, an d eye lid dro o p ing. In acute oral expo su res, sig n s a p p eare d

as soon a s 2 0 minutes p o s tadmini s tration in malla rd s and 2.5 h o u r s in ph ea san t s. Death s occurre d betwe en 4 and 48 h ours in mallards a nd 2 and 6 d a y s in phea sa nts; remi ssi o n took up to 7 days (Hud so n et al. 1984). In

s t udies with coturnix ( Coturnix coturnix coturnix ), (Hill 1981 ) found t hat methylme rcu r y wa s al ways more toxic than inorgani c mercu r y, an d that young bird s we re u s uallymore se nsitive than ol der bi rd s. Furthermo re, so me bird s poi son e d by inorga ni c mercu r y re covered afte r tr eatme nt wa s withdra w n, b u t chicks that were fed



### 36methylmercu ry and later de veloped toxic sign s u s ually died, even if treated fee d was re moved. Coturnix subj ecte d to inorg ani c mercury, re gardle ss of route of admini s tratio n, sho w ed a violent neurol ogical dysfun ction
that ended in death 2 to 6 h ours po sttreat ment. The wi t hdra w al synd rome in coturnix poiso ned by Hg 2 + wa s
usu a lly pre c e ded by interm ittent, nearly undete c tabl e trem ors, coup led with ag gressi vene ss towards coh o rt s; time from on set to remissio n wa s usually3 to 5 days, but sometim e s extende d to 7 days. Cotu rnix poisone d by methylmercu ry appeared n o rmal u n til 2 to 5 days po st tr eatment; then, ataxia an d low bo dy ca rria ge with outstret c he d neck were oft en asso ciate d with wal k in g. In advance d stage s, cot u rnix lost lo co motor coordin a tion and did n o t re cover; in mild to moderate clini c al si gns, recove ry usu a lly took at least 1 we ek (Hill 1981).

Merc ury toxicity to birds varies with the form of the ele m ent, dose, route of admin istration, spe c ie s, sex, age , and phy siolo g ical con d ition (.Fimreite 1 979). Fo r exa m pl e, in north ern bo bwhite chi c ks fed die t s contai ning methylmercu ry chlorid e , mortality was si gnifica ntly lo wer whe n the solvent wa s aceto ne than whe n it was anothe r ca rri er su ch a s p r opylene gly c o l or co rn oil (Spann et al. 1986 ). In addi tion, organ om ercury compo und s intera ct with elevated tem peratu r e s an d pesti cide s, su ch a s DDE and pa rathio n , to produ ce a dditive or morethan-a dditive toxicity, and with sel enium to produ ce le ss-than -a dditi ve toxicity ( Fim r eite 1979). Acute oral toxicities of variou s me rcury formulation s ran ged b e tw ee n 2.2 and about 31.0 m g /kg bo dy wei ght for most a v ian spe c ie s teste d (Tabl e 8). Similar data for other ro utes of administ r at ion we re 4.0 to 40.0 mg/kg for diet and 8. 0 to 15.0 mg/kg body weig ht for intramu scular inje ction (Tabl e 8).

Re sidu es of mercury in ex perim entally poisone d pa ss eri ne bi rd s u s ually exceed ed 20 mg/kg fresh wei ght, and were sim ilar to con c e n t rations rep o rted in wild bi rds that died o f mercu r y poi soni ng (Fi n le y et al. 1979). Mercury level s in tissue s of poiso ned wild bird s we re highe st (45 to 126 mg/kg fresh weig ht) in red

- wi nged blackbi r d s ( A gelaiu s pho e n ice u s), intermediate in st arling s ( Stur nu s vu lgar is) a nd co wbi r d s ( Molothrus ater ), and lowe st (21 to 54) in g r a ckl e s ( Q u iscalu s quiscul a ); in gene ral, Hg resid u e s we re highe st in the brain, follo wed by the liver, kidn ey, muscle, a nd ca rcas s. Some avian sp ecie s are more se n s itive than pa sserin e s (Solo nen a nd Lode niu s 198 4): liver re sid ues (i n mg Hg/kg dry weig ht) in bird s ex perim entally killed by meth ylmercury ra n ged from 17 in re d-tailed h a wks ( Buto jam a icensi s) to 70 in jackda ws ( Corvu s m one dula ); an d values were interme d iate i n ring -ne c ked phea sant s, kestrel s ( Falco tinnunculu s), and magpi es ( P i ca pi ca ). Experimentall y poisone d gre yheron s ( Ard ea cin e re a ) seemed to be unu sually re si stant to Hg; lethal do se s p r odu ce d re sid ues of 415 to 752 mg Hg/ k g dryweight of liver (Van de r Mo len et al. 198 2). Ho weve r, levels of this magnitud e were freque ntly encou ntere d in livers fro m gre yheron s coll ect ed d u rin g a massive die

- off in the Net herla nd s du ring a cold spell in 1 976; the interaction effe cts of cold st ress, mercu r y loading, an d po or physi cal co ndition of the hero n s a r e u n kn own ( ( Ard ea cin e re a ) in the Netherl a nds. Arde a 7 0 :173-184V a n der Mol en e t al. 1982).

Table 8. Toxicity to birds o f mercu r y ad ministe r ed byoral, dietary, or othe r route s

.

Route of adm inistratio n (units), org ani sm, and Exposu r e mercury form ulation Con c e n tratio n interval Effect Referen c e a

Acu t e oral (mg Hg/kg
bod y w e igh t )
C h uk ar , A l ect o ris chu k a r Ethyl 26.9 Within 14 d LD-50 Hud s o n posttre a tment et al. 1984 Mallard, Anas platyrh y

n c h o s Methyl 2.2–23.5 " LD-50 Ethyl 75.7 " LD-50 Phenyl 524.7 " LD-50
North e rn bob white, Colinus virgi n ianus



### 37Methyl 23.8 " LD-50 Coturnix,
Coturnix c o t u rnix c o turnix Methyl 11.0–27.0 " LD-50 Hill 1981 Inorga nic 26.0–5 4.0 " LD-50 Jap ane se q u a il,
Coturnix japonica Methyl 14.4–3 3.7 " LD-50 Hill and
Soare s 19 84;
H u d s o n
et al. 1984
Eth y l 2 1

. 4 " L D -5 0 H u ds on
et al. 1984 Inorga nic 31.1 " LD-50 Hill and
Soare s 19 84
Ro ck d o v e , Colum ba livia
Eth y l 2 2

. 8 " L D -5 0 H u ds on
et al. 1984
Fulvous whi s tling du ck, Dendrocygn a bicol o r Methyl 37.8 " LD-50
Dome st ic chi c k en, Gallus dom esticus Phenyl 60.0 " LD-50 Mullins

et al. 1977
H o us e s p ar row , Passe r dom esticus Methyl 12.6–3 7.8 Within 14 d LD-50 Hud s o n posttre a tment et al. 1984 Gray pa rtridg e, Perdix perdix Ethyl 17.6 " LD-50 Ring -ne c ked phea sa nt,
Phasianu s colchi cu s Ethyl 11.5 " LD-50 Methyl 11.5–2 6.8 " LD-50 Phenyl 65.0–1 01.0 " LD-50 Mullins

et al. 1977;
H u d s o n
et al. 1984
Prairie chi c ke n, Tym panuch u s cupid o Eth y l 1 1

. 5 " L D -5 0 H u ds on
et al. 1984



### 38Dieta r y (mg Hg/kg diet)
Cotur n ix Inorganic 32.0 Hatch- 9 weeks LD-0 Hill 1981 Inorga nic 2,956– 5,086 5 d + 7 d pt LD-50 Methyl 4.0 Hatch-9 wee ks LD-0 Methyl 8.0 5 d Some Hill and
death s Soare s 19 84 Methyl 31.0–47.0 5 d + 7 d pt LD-50 Hill 1981 Ring -ne c ked phea sa nt Ethyl 4.2 70 d LD-0 b Spann Ethyl 12.5 70 d LD-50 et al. 1972 Ethyl 37.4 28 d LD-50 Ethyl 112.0 15 d LD-50 Jap ane se q u a il Inorga nic
In dry salt 500 28 d LD-86 El-Begea rmi
In ethanol, et al. 1980 methanol, o r water 500 28 d LD-55
In casein pre m ix 500 28 d LD-33

Birds, 4 spp.

Methyl 40.0 6 to 11 d LD-33 Finley

et al. 1979 Intramuscular injection (m g Hg/kg b o dy w e igh t)
Cotur n ix Methyl 8.0–33.0 Single do se LD-50 Hill 198 1 Inorga nic 15.0–5 0.0 Single do se LD-50
Ro ck d o v e Inorga nic 10.0 Daily, 17 d Some Lean der
death s et al. 1977 Yolk sac injection (ug Hg/e gg)
Chi c ken Methyl 15.0 Single do se Some Gree ne r and death s Koche n 198 3 Methyl 40.0-5 0 .0 Single do se LD-50 Applied to E gg Surfac e ug Hg/egg
Mallard Methyl 3.0 Single do se LD-0 Hoffman an d Methyl 9.0 Single do se Some Moore 197 9
death s



### 39In drinking w a te r (mg Hg/L)
Chi c ken Inorga nic 500.0 3 d Some Gri sso m and
death s Thaxton 198 5

a Refe ren c e cited applie s to data in the same ro w an d in the rows that immediat ely follow for whi c h no refe ren c e is indi cated.
b Re du ction in egg pro d u c tion, 55% to 80%; embryoni c su rvival sha r ply red u ced.

Table 9 . Toxicity of organ omercu ry co mpoun ds to selecte d mam m alian spe c ie s.

Do se, route o f admini s tratio n, and Orga nism other vari able s Effects Refere nce

Dog, 0.1 to 0.25 mg/kg bo dy High in cide nce Khera 1 979

Cani s fam iliaris weight during entire of stillbirths

preg nan cy; oral route Cat, 0.25 mg/kg b ody Mean surviva l Eaton

Felis dom esticus weig ht daily for 90 time 78 days. et al. 1980 days (total 80 –90 Convul sion s mg Hg ); dieta r y starting at da y
route 68; all with sign s by day 90.
Liv e r re sid u e s of survivors
were 40.2 an d
18.1 mg/kg
fresh weig ht for
total mercury and inorg ani c mercury,

r e spec tively Pig, Sus spp. 0.5 mg/kg bo dy weight High in cide nce Khera 1 979 during pregnancy; oral of stillbirths

route
Rhe s u s mon k ey, 0.5 mg/kg bo dy weight Matern ally Khera 1 979

Maca ca m u la tt a durin g days 2 0–30 of toxic, and

preg nan cy abortie n t Mink, 1.0 mg/kg in diet Fatal to 100 % Sheffy and

Mustela vison in about 2 mo nths St. Amant 1982
2 months River otter, >2.0 mg/ k g in diet Fatal Kuce ra 19 83



### 40Lutra cana de nsi s Mink 5.0 mg/kg in diet All dead in 30 Sheffy and to 37 days. St. Amant 1982
Elevated re si due s in kidn ey (37.7 mg/ k g fresh weig ht) and liver (55. 6) prio r to death
Huma ns Variou s Lethal re sid u e s Khera 1 979
in tis s u es , in mg/k g fres h weig ht, were >6.0 in brain, >10.0 in liver,
and >17.0 in
whol e body
Mule dee r, 17.88 mg/kg LD-50 Hud s o n

Odo c oile us h e m i onus body wei ght; singl e et al. 1984
hem ionus oral do se Harp se al, 25.0 mg/kg b ody Dea d in 20 to Ron a ld

Pagophilu s weig ht daily; oral 26 days. et al. 1977

groe nlan dicu s route Blood Hg lev e ls just before
death were 26.8 to 30.3 mg/L

MAMM ALS Methylmercu ry affects the central ne rvo u s sy stem in man--e spe c ia lly the sensory, visual, and auditory a r ea s
con c e r ne d wi th coordinatio n; the most severe effect s lead to wid e sprea d brain d a mage, resulting in mental dera nge ment , coma, and d eath (Cl a rkso n and Ma rsh 1982 ). In mule deer ( Od ocoileu s hem ionus h e m i onu s ), after acute oral Hg poi so ning wa s ind u ced experi m en ta lly, additional sign s in clu ded bel chin g, bloody diarrh ea, piloerectio n (hair mo re e r e c t than usual), and loss of appetite (Hud son et al. 198 4). The ki dne y is the proba ble critical organ in adult mam m als du e to the rapi d deg radat ion of ph enylmercu rial s and meth oxyethylmercuri a ls to inorg ani c Hg comp oun ds a nd su bsequ e n t translo cati on to the kidn ey (Suzu k i 19 79), wh erea s in the fetus the brain i s the princip a l target (Khera 197 9). Most hum a n poisoning s were a s soci ate d with org ano mercury comp oun ds u s ed in a g ri cul t ure as fu ngicides to protec t cereal see d grain (Elha s sani 198 3); jud g ing from

ane cdotal evi den ce, many wildlife spe c ies may have been simila rly afflicted. Org anome r cury compou nd s, esp e ci ally methylmercury, were the mo st toxic mercu r y speci e s te sted. Among sensitive spe c i e s of mamm a l s, death o c curre d at daily org anome r cury concentratio n s of 0. 1 to 0.5 mg/kg bo dy weig ht, or 1.0 to 5.0 mg/kg in the diet (Tabl e 9). Larger a n imals su ch a s mule de er a nd harp se als appea r to be more resi sta n t to Hg than smalle r mam m als such as mink, cats, d ogs, pig s , mo nkey s, and ri ver otters; the reason s for this differe nce are unkno wn, butmay be relat ed to differen c e s in metab o lis m an d det oxication rate s. Tissue resi due s in fatally poisone d ma mmals (i n mg Hg/kg fresh weig ht) we re 6.0 in brain, 1 0 .0 to 55.6 in liver, 17.0 in whol e body, about 30.0 in bloo d, and 37.7 in kidney (Ta b le 9).



### 41OTHE R GR O U PS Methylmercu ry compou nd s at concentrat i ons of 25.0 mg Hg/ k g in soil were fatal to all tiger worms ( Eise nia foetida ) in 12 wee k s; at 5.0 mg/kg, ho we ver, only 21% died in a simi lar pe riod (B e y er et al. 1985). Inorga nic mercury com poun ds were also toxic to e a rthworm s ( O c tochaetu s p a ttoni ); in 60 days, 50% di ed at soil Hg levels of 0.79 mg/kg

, and all died at 5.0 mg/kg (Abbasi a nd S oni 198 3).

SUBLETHAL EFFECTS

GENERAL Mercury is a kno w n muta g en, teratoge n , and ca rcin o gen. At comparatively low con c entratio n s in birds a n d mammal s , it adversely affects rep r od uction, growth a nd develo p m ent, behavior, blood an d se rum chemi s try, motor coordin a tion, vision, heari ng, histo l ogy, and metaboli s m. It h a s a hi g h pot ential for bioa ccumulatio n and biomag nificati on, and is slo w to depu rate . Organom ercu ry comp ou nds were more effective in prod uci ng adverse effects than we re i norg ani c Hg comp oun ds; however, effects were signi ficantly enha nce d or amelio rated b ynumero u s b i otic and n o n b iologi cal mo difier s. Fo r sensitive aq ua tic spe c ie s, a d verse effect s were ob se rve d at water co nce n tration s of 0.03 to 0.1 ug Hg /l. For sen s itive sp e c ie s of bird s, harmful level s we re 640 ug Hg/kg body weig ht daily, or 50 to 500 ug Hg/kg in t he diet; for se nsitive mammal s , these level s we re 250 ug Hg/ k g bo d yweight daily , or 1,100 ug Hg/kg diet.

AQ UATI C O R G ANISMS Mercury at co mparatively low con c entra tions adve r se ly affects the rep r od uctio n , gro w th, beha vior, metaboli s m, blood chemi s try, osmoregu lation, and oxygen exch an ge of marin e and fre s h w at er organi sm s. In gene ral, the a c cumulatio n of mercury byaquatic bi ota is rapid, an d depu ration i s slo w . It is empha sized that orga nom ercu ry comp oun d s , esp e ci ally methylmercu ry, were sig n ificantly more e ffective than inorg ani c mercury comp oun ds i n prod uci ng a d verse effect s and a c cum u lation s.
Rep r od uctio n was in hibited among sen s i t ive speci e s o faquat ic orga nism s at wate r con c e n tratio ns of 0.03 to 1.6 ug Hg/l. In the plana ria n (Best et al. 1981 ); in the slipp e r limpet( Crepid u la fo rnicata ), spa w nin g wa s de layed and fecunditywas d e crea sed at 0.25 ug Hg 2+ /l (Thain 1984); in the zeb r afish ( Brach y

d

anio rerio), hatchi ng

su ccess was redu ce d at 0.1 ug Hg 2+ /l and egg d epo sition wa s red u ce d at 0.8 ug/l (Armst ron g 1979 ); fathead minno ws ( Pim ephales p r o m elas) expo sed to 0.12 ug methylmercu ry/l for 3 months failed to re prod uce (Birg e et al. 1979); the leopa rd fro g ( Ran a pipien s) did not meta morp ho se du ring expo su re to 1.0 ug methylmercury/l for 4 months (EPA 1980); and in the mysid shrimp ( Mysid opsi s

ba hia ), the abortio n rate increa sed and pop ulati on size de cre a sed after lifetime (i.e., 28 days) expo su re to 1.6 ug/l of mercu r y as mercuri c chlo ride (Gentile et al. 1983 ). For sensitive ma ri ne inverteb rat e s such as hy droid s , protozoan s, and mysid shrim p , re prod uctio n was inhibited at concentratio n s betwee n 1.1 and 2.5 ug Hg 2+ /l; this range was 5 to 71 ug/l for more res i s t ant s p ec ies of marine inv e rteb rate s (G entile et al. 1983).

Red u ced gro w th of sen s iti v e spe c ie s of aquati c org a n i sms h a s b e e n recorded atwater con c e n tration s of 0.04 to 1.0 ug Hg/l. The rai nbo w trout ( Sa lm o gairdne ri ) wa s the mo st sen s itive speci e s te sted ; growth reduc t ion was obs e rved after 64 days in 0.04 ug Hg/l as methylmerc ury, or 0.11 ug Hg/l as phenylmerc u ry (EPA 1980 ). In adults of the ma rine moll usc Cre p idul a fornicata , growt h wa s red u ce d after 16 we eks in 0.25 u g Hg 2+ /1 (Thai n 1984 ). Gro w th inhibition wa s re co rde d in fresh w ate r algae after e x posu r e of 24 hours to 10 d a ys to 0.3 to 0.6 ug orga nom ercury/l, in bro o ktrout ( Sal v el

inus fontin alis) alevins afte r exposu r e for 21 days to 0. 79 ug organomercury/l (EPA 1980), and in the marine al ga Scri psi e lla faeroen se ex posed to 1.0 ug Hg 2+ /l for 24 hours (Kay se r 1976 ).
Adverse effects of mercury to aquatic o r g anism s, in ad dition to those listed on re prod uctio n an d gro w th, have bee n do cume nted at water con c e n t rations of 0.8 8 to 5.0 ug/l: enzyme di sru p tion in bro o k trout ( Salvelinus fontinalis) em bryos imm e rsed for 17 day s in sol u tions cont ai ning 0. 88 ug/l, as m e thylmercury (EPA 1980); an increa sed in ci den ce of frust u le abn orm a lities and b u rst thecae in two spe c ie s of marin e algae durin g expo sure to 1.0 ug Hg 2+ /l for 24 hours (K ayse r 19 76; Saboski 1 977); a rre st e d developm e n t of sea urch in larvae at 3.0 ug Hg 2+ /l for 40 hours (EPA 1980); de creased rate of intestinal transpor t of glucose, fructose, glyci ne, and



### 42tryptophan in the murrel ( Chann a pun cta tus) at 3.0 ug Hg 2+ /l for 30 days (Sa s try et al. 1982); a l tered blo od
chemi s try in striped ba ss ( Morone saxatilis) at 5.0 ug Hg 2+ /l in 60 days (Da w so n 1982 ); and decrea s e d respiration in stripe d ba ss 30 day s p o st exposure afte r immersio n for 30 to 120 days in 5.0 u g Hg 2+ /l (Armstro ng 1979; EPA 1980). In mari ne molluscs exposed to water concentrat ions of 6 to 10 ug Hg 2+ /l for 96 ho urs, the feeding of ad ults ce ased a nd the swim ming rate of l a rval stag es decli ned (Tha in 1984 ). At 44 ug Hg 2+ /l for 30 days, the fre s hwate rfish Notopteru s not opteru s sho w ed gen erali z e d metaboli c d e ran gem ent (Verma an d T onk 1983 ). In fresh w ater pl an arian s expo sed to 80 to 10 0 ug/l as met h ylmercury, b ehavior wa s modified an d rege ne ration retarded (B est et al. 1981). And at high subl ethal con c entration s of methylmercu ry, rainbow tro u t were listle ss and da rkly pi gmented; ap p e tite was re d u ce d, and dig e stion wa s po or (Rod gers a nd Beami s h 1982 ).

At lower trop hic level s , the efficiency of mercury tr a n sfer wa s low th roug h natu r al aquatic foo d chai ns; however, in a n imals of hig her tro phi c le vels, su ch a s pred atory tele osts a nd fish -eating birds a nd mammal s , the transfe r was markedly am plified (Eisl e r 1978, 19 81).
High u p take and a c cumul a tion of mercury from the medium by re pre s entative spe c ie s of marine a nd fresh w ate rtel eost s and inv e rteb rate s ha ve been do cu ment ed (Ko p fler 197 4; Eisl er 197 8, 198 1; Birge et al. 1979; Hucka bee et al. 1979; EPA 1980, EPA. 1985; Stokes et al . 1981; Rodgers and Beam ish 1982; Hi rot a et al. 1983; Cla r kson et al. 19 84; McClurg 1984; Niimi a nd Lo we-Jin d e 1984; Ram a moo r thy and Blumhage n 1984; Ribeyre and Boudou 1 984 ; Thain 1984 ). Accumulati on pattern s were en han ce d or signifi cantl ymodified by numerous biological and abiotic factors (NAS 1978; Eisl er 1978, 1981, 1984, 1985; EPA 1980, 1985; Stokes et al. 1981;Rod gers and Be a m ish 19 82; Cl arkso n et al . 1984; Rama moorthy an d Blumhag en 1 984; Rib e yre and Boudou 1 984 ). In general, the accumul a tion of me rcury wa s markedly enha nce d at elevated water temperature s , reduced water sali nity or hard n e ss, red u ce d wate r p H , increa sed age of the organi sm, and redu ce d orga nic matter co ntent of the m edium; in the pre s en ce of zinc, ca dmium

, or seleni um in solutio n ; after increa sed d u ration. of exposure; and in the pre s e n ce of incre a sed nominal con c entration s of protein

- b oun d mercury. Upt a ke p a ttern s were sig n ifica n tly modified by sex, sexua l conditio n , prior histo r y of exposure to Hg salts, the p r e s en ce of com p lexing and chelating a gen ts in solutio n , dietary co mp osition, feedi ng niche, tissue spe c ificity, an d metaboli s m ; however, tre nds were not con s i s tent be tween spe c ie s and it is difficult to gene ra lize. In one examp l e, Ribeyre a nd Boudo u (1 984) imm e rse d ra inb o w tro u t in solution s containi ng 0. 1 ug Hg/l, as methylmercu ry: after 30 days, bioco n cen t ration facto r s (BCF) ran g e d from 28,30 0 for brai n to 238,00 0 for sple en; value s we re inte rm ediate for mu scl e (30,0 0 0 )

, whole fish (3 6,000), blo od (102,0 0 0 ) , liver (1 10,00 0), kidn ey (137,0 00), and gill (163,00 0). Th e values ma yhave been hi gher if expo sure ha d exten ded beyo nd 3 0 days; Ro dge rs and Bea m ish (198 2) sho w ed that whol e body Hg re sidu es in rain bow tro u t sub j ected to me rcury insult continu ed to increa se for the first 66 days b e fore stabili zing. Whe n mercu ry was p r esen ted as ino r ga nic mercuri c ion at 0.1 ug/l for 30 days, BCF values were usu a lly lowe r than in trout e x pose d to methylmercury: 2,300 for mu scle; 6,800 for brain; 7,00 0 for wh ole tro u t; 14,300 for bl ood; 25,00 0 for liver; 53,00 0 for kidn ey; 68,600 for gill ; and 521,00 0 for splee n (Ribeyre an d Boudo u 198 4). The high BCF values reco rded fo r rain b o w trout we re probably du e to efficient upta k e from wate r, couple d with slow d epu rat i on (Rodg ers and Beami s h 1982 ). Whol e body levels up to 100 mg Hg/kg we re repor te dly not lethal to rainb o w trout, alth ough 2 0 to 30 mg/kg were a s soci ated wit h redu ce d ap petite, loss ofequilibri um, and hype rpla sia of gill epit helium (Niimi and Lowe-Jind e 1 984). Ho wev e r, bro o k trou t showed toxic si g n s a nd d eath at whol e body resi due s of only 5 to 7 mg/kg (A rm strong 1 979 ). In anothe r exa m ple, the marine co pep od Acartia clau si , subje c ted to 0.05 ug/l of mercury an d highe r, rea c h ed equilib riu m with the medium in only24 hours. In that study (Hi r ota et al. 198 3), BCF value s for wh ole Acartia after 24-h our expo su re s we re 14,3 6 0 for inorgani c mercu r ic io n (0.05 ug/l ) and, for methylmercu ry, 179,200 (0. 05 ug/l) an d 1 81,000 (0.1 u g /l).

Elimination ofaccumulate d mercury, bot h orga nic a n d inorga nic, fro m aquatic o r g anism s is a complex multicom part m ental proce ss, but ap pea rs to be la rgel y depend ent on its rate of biologi cal a s similation. This rate, in turn, varie s wid e ly (20% to 90%) betwe en sp e c ie s, for rea s ons a s yet un explained (NAS 1978). For example, mercury a s soci ated with dieta ry compon ent s that are n o t assimilated i s eliminated ra pidly with feces. The re st is ab sorbed a c ro ss the gut and inco rpo r ate d into tissu es. This a s similat ed fractio n of mercury is depu rated m u ch mo re slo w ly, at a rate positively co rrelated with th e orga nism's metaboli s m (NAS 1978; Rod gers an d Beamish 198 2). Time to eliminate 50% of biologi cally assimil a ted mercury an d its com poun d s (Tb 1/2) is vari abl e. Among various spe c ie s of fresh w ate r teleost s , Tb 1 /2 values (in days) we re 2 0 for guppi es



### 43Poecilia reticulatus , 23 for goldfish Ca ra ssius a u ratu s , 100 for nort hern pi ke, an d 1,000 ea ch for mosquitofi sh Gam busia aff i nis , bro o k tro u t, and rainb o w trout ( Hu ckabee et al. 1979). simil a r ra nge in. Tb 1/2 values wa s recorded for i n verteb rate s and ma rine fi she s : 297 d a y s for the cra y fish Astacus fluviatilis , 43 5 days for mu ssel, 481 day s for the clam T ape s de cu ssatus 1,030 day s for the eel Anguilla vul gari s , and 1,20 0 da ys for the flounde r Pleu rone cte s flesus (NAS 197 8).
Mercury

- tolerant strain s of bacte ria (Col well et al. 197 6), proto z o a (Berk et al. 19 78), cru s tace ans (Green et al. 1976; Wei s 197 6), and f i sh (Wei s 198 4) have be en r epo rted. It has be en sugg ested that the mercuryresi stant strai n s of ba cteria that have been cultu r ed o r discovere d may have ap plicatio n in mobilization or fixation of mercu r y from co ntaminated a quatic e n viro nments to the extent that p o lluted area s may beco m e inno cuo u s (Colwell et al. 1 976). The m a rine p r oto z o an Uronem ia nigri can s , after feedin g on Hg-l ade n ba cteria, acq u ire d mercury tole ran c e within a si n g le gen eratio n (Berk et al. 1978 ). The white shri mp ( Penaeu s setiferu s), preexp o sed for 57 day s to 1 ug Hg/l, did not differ from c ontrols d u r ing eithe rex posure o rsub s eq uent Hg stress experim ents (Gree n et al. 1976); this o b servation sugg es ted that no nse n siti zation or adaptatio n mecha n isms are involved. The fiddler crab ( Uca p ugil a tor ) seem ed unusually re sista n t and showed ne gligi b le upta k e or effects du ring exposu r e to 100 ug Hg/l for 2 we eks (Wei s 197 6). Rea s o n s to a c count for Hg adaptation ofthe estua r ine cyp r inod ontiform teleost F u nd ulu s h e t er

oc litu s to both me thylmercury a nd inorgani c mercury a r e unde r investi gation (Wei s 1984 ).

BIR D S
Sublethal effe cts of mercu ry on birds, ad ministe r ed bya variety of routes, in clud ed adverse ef fects on gro w th, devel opment, re produ ction, blo od and tissu e chem i s try, metaboli s m, an d behavio r; histopath o logy and bioa ccumulati on we re al so noted.

The dieta r y route of admin istration i s the most exten s ively studie d pathway of a v ian Hg inta ke. Dome stic chi c ken s fed diets containi ng as little as 50 ug/kg of mercury, as m e thylmercury, contai ned el e v ated total Hg (2.0 mg/kg fresh weig ht) resid u e s in liver and kidn ey a fter 28 wee ks; at 150 u g /kg, re sidu es range d from 1

. 3 to 3.7 mg/kg in heart, mu scl e , brain, kidn e y , and liver, in that general orde r; at 450 ug/kg in diet s, re sidue s in edible chi c ken tissu e s (3.3 to 8.2 mg/kg ) we re con s id ere d h a za rdo u s to h u man con s u m ers, althoug h no overt sig n s of mercury toxicosi s we re ob served in the chicken s (M arch et al. 1983 ). High ino r g anic me rcury levels (5 00 m g /l) in drin king wa ter of chi c ken s de cre a sed gro w th rate a nd food an d water con s u m ption, and e l evated hemo g lobin, hemato c rit, a nd erythrocyt e conte n t within 3 days (G rissom a nd T haxton 198 5). The dietary con c e n tration of 0.5 mg Hg/ k g dryweight (e qui valent to abo ut 0.1 mg/kg fresh weight) in the form of methylmerc ury was fed to three gene ration s o f mallard s (Heinz 1 979 ). Female s laid a greate rpercentage of thei r egg s outsi d e nest boxe s than did co ntrol s , and al so laid fewer e g g s a nd pro d u c ed f e we r du ckli n g s . Ducklin gs from pa rents fed methylme rcu r y were less respon sive than controls to ta pe-re corded ma tern al call s, but we re h y perrespon si ve to a fright stimulu s in avoidan ce te sts. The tissue s and egg s of du cks and ot her spe c ie s o f birds colle cted in the wild have sometim e s containe d leve ls of mercu r y equal to, or fa r excee d ing, those asso ciat ed with re pro ductive an d behavio ral de ficien cie s in d o mesti c malla rds (e.g., 9 to 11 mg/kg in f eathers; >2.0 mg/kg in oth e r tissue s); therefo r e, it is possible thatr eprodu ction and be havior of wild bird s h a ve been mo dified by methylmercury contami natio n (Hei nz 1 9 7 9 ). Tissue m e rcury re sid u e s of wild -st r ain malla rd s and gam e-fa rm mallard s were not signifi cantly d i fferent after the bird s were fed diet s co n t aining 0.5 m g Hg/kg as m e thylmercury for extended perio ds--i ndi cating that ga me-farm mall ard s are suita b le su bstitute s for wild m a ll ard s in toxicol ogical evaluat ions (Hei nz 1 980 ). Dietary con c entration s of 1.1 mg total Hg/kg have b een a s soci ated with ki dne y lesion s in ju venile starlin gs ( Sturnus vul ga r is) and with elev ated re sidu es in the liver(6 .5 mg/kg dry weig ht and ki dney (36.3 mg/kg ) , after exposure fo r 8 >wee ks (Ni c hol so n and Osb o rn 1 984 ). In America n black du cks ( Anas rub r ip es) fed diets cont aining 3.0 mg Hg/kg a s me thylmercury for 28 wee ks, rep r od uctio n wa s sig n ifica n tly inhibited; tissu e re sidu es were el evated in kid n e y(16.0 mg/kg fresh weight ) and liver (2 3.0 mg/kg ) ; and brain le sion s cha r a c teri stic of mercu r y p o iso n ing were pre s ent (Finley and Sten dell 197 8). Japan ese quai l ( Cotu rni x japoni ca ) fed diets containi ng 8 mg Hg/ k g of inorga ni c mercury for 3 wee k s had depresse d go nad weight s; those fed 3 m g /kg ino r ga ni c mercu r y or 1 mg/kg meth yl mercury for 9 wee k s sh o w ed alte ratio n s in brain an d plasm a en zyme activities (Hill and Soa r es 19 84). Grossly elevate d tissu e re si d ues of 40 0 mg/kg in feathe rs an d 17 to 130 mg/ k g in othe r tissue s were m easure d in gray partrid ge ( Perdi x

perdix ) after dieta r y exposu r e of 20 to 25 mg total Hg/kg for 4 we eks (M cEwe n et al. 1973).



### 44Mercury expo sure by imme rsio n and o r al administ r atio n have ca use d rep r od uctiv e and be havo r ial modific a tions

. Brief immers ion of ma lla rd egg s in sol u tions of met h ylmercur y re sulted in a sig n ificant in cide nce of skel e tal e m bryoni c ab e rratio n s at do sag e s of 1. 0 ug Hg/e gg, a nd high er; no increa se s in embryo nic malformatio n s we re note d at 0.3 ug Hg/ egg (Hoffman and Moo r e 1 979). Re du ced rep r o d u c tive ability was noted in grey phea sa nts in gestin g 640 u g Hg (a s o r ga nom e r cury)/ kg body wei g h t daily for 30 days (M cEwe n et al. 1973); si m ilar re sult s we re ob se rved i n ring -ne c ked phea sant s (Spann et al. 1972; Mullin s et al. 1977). Behavioral alteration s were noted in pige ons ( Colu m ba livia ) give n 3,000 ug in organi c Hg/ k g b ody daily for 17 days (L ean de r et al. 1977) or 1,000 u g /kg body wei g h t of methylmercu r y for 5 we eks (Evan s et al. 1982). Observed b e havioral cha n ges in p o stu r e and moto r coor di nation ofpigeon s were perm ane nt after the brai n accumul a ted >12,0 00 ug Hg/kg fre s h we ight, and we re simila r to the "spa stic pa ralysis" ob se rv ed in wild cro w s durin g the Mi namata, Ja pa n, outbrea k ofthe 1950' s, a l t hough b o th spe c ie s survi v ed for years with these sig n s (Evans et al. 1982 ).
Mercury resi d ues of 79 0 to 2,000 ug/ kg i n egg, and 5, 000 to 40,00 0 ug/kg in feat hers, are lin ked to impaire d rep r od uctio n in variou s bird spe c ie s (Spa nn et al. 1972 ; NAS 1978; Hein z 19 79; Fimreite 1979 ; Solonen an d Lode niu s 198 4). Re sidue s in eggs of 1, 300 to 2,000 ug Hg/ k g fre s h weig ht were asso ciated with red u ced hatchi ng success in white

- tailed sea-eag les ( Haliaeetus albi cilla ), th e comm on lo on ( G a v i a

i

mme r ), and in several se ed -eating spe c ie s ( Fimreite 1979); this rang e wa s 900 to 3,100 ug/ kg for rin g -n ecke d phea sa nt (Span n et al. 1972 ), and 7 90 to 860 ug/ kg for mall ard s (Hein z 197 9). Re sidue s of 5,000 to 11,000 ug Hg/ k g in feathers of variou s sp eci e s of birds h a ve been a s so ci a t ed with red u c ed h a tch of egg s and with sterility (NA S 1978 ). Sterility was ob serv ed in the Finn ish sparro w h a wk ( Accipite r nisu s) at me rcu r y co ncent ration s of 40,000 ug/kg in feath e rs (Solon en and Lo deniu s 1984). Chi c ks of the com m on tern ( Sterna hi run d o) f r om a colony in Long Isl and, Ne w York, with abno rmal fe ather lo ss, ha d si gnifi cantlyelevated mercury level s in blood a nd liver (Go c hfeld 1 9 80); ho weve r, the linkag e o ffeather loss to mercury co ntamination requires fu rthe r examinatio n

.
Interactio n effects of me rcu r y with other contami nant s, such a s he rbicid es a nd p e stici d e s , cou l d intensify hazard s to avian pop ulatio ns (M ullin s et al. 1977). For exam pl e, a strikin g pa ral l el exists bet wee n levels o f Hg and of DDT a nd its metabo lites in bird s o f prey, sugge sting the exist ence of com m on ecotoxicologi cal mech ani sm s (Del be ke et a l . 1984; Wiem eyer et al. 1984); additio n a l rese arch i s clea rly need e d

.
MAMM ALS Mercury has no known phys iologi cal function (EPA 1985). In hum ans and other mammals, it causes teratoge nic, mutageni c, a nd ca rci nog e n ic effect s; t he fetus is the most sen s itive life stage (NAS 1978; Chang 1979; Khera 1979; EPA 1980, 1985; Elhassani 1983; Green er and Kochen 1983; Clarkson et al. 1984). Methylmercu ry irreversibly destroys the neuron s of the c entral ne rvous system. Freq uently, a sub s tantial lat ent perio d interve nes b e twe en the ce ssation of exposure to Hg an d the onset of sign s and sympto ms; this interval is

usu a lly measured in wee k s or mo nths, but sometim e s in y ears (Cl a rkso n et al. 1984 ). At high subl ethal d o se s in
man, mercu r y cau s e s ce re bral pal sy, gross motor a n d mental imp a irme nt, spee ch di sturb a n c es, blind n e ss, deafness, microcephaly, intestinal di sturbances, trem ors, and tissue pathology (Chang 1979; EPA 1980, 1985; Elhassani 1 9 83; Clarkson et al. 1984). Pathologi cal and ot he r effects of Hg m a y vary from orga n to org a n , depe nding o n factors su ch as the effecti v e toxic dose in the orga n, the com pou nd involved and its metabolism within the org an, the durati on of ex posure, and the oth e r co ntamin a n ts to whi c h the animal i s concurrently exposed (Ch ang 19 79). Many com p o und s--e spe c i a lly sa lts of selenium --prot ect huma n s a nd other a n im als against mercury toxicity, although thei r mode of action is not clear (NAS 1978; Chang 1979; EPA 1980, 1985; Eisler 1 985 ).
Adverse effects of orga nom ercury compo und s to se le cted spe c ie s o f mammals h a ve been recorde d at admini s tered doses of 0.25 mg Hg/kg bo dy weight dail y , di etary levels of 1.1 mg/ k g, and bl ood Hg levels of 1.2 mg/l (Table 1 0 ).
Mercury tra n sfer and bio m a gnificatio n through ma mma li an food chai ns is well do cumented (Gal ster 19 76; NAS 1978; Eaton et al. 1980; Eisler 1 9 8 1 ; Hucka bee et al. 1981; Sheffy and St. Amant 1982; Kuce ra 19 83; Clarkson et al . 1984; Wren 1986 ), but co nsid era b le va riat ion exist s . Among terre s trial mam m a l s, for exampl e, herbivo re s su ch a s mule d eer, moo s e ( A l ces al ce s), cari bou ( Ran g ifer tara ndu s), and vario u s spe c ie s of ra bbits

usu a lly contai ned le ss tha n 1.0 mg Hg/kg fresh weig h t in liver and kidn ey, but carnivo r e s su ch as the ma rten ( Marte s m a rt es), pol ecat ( Mustela p u torius), an d re d fox ( Vulpes vulpes) freq uent ly containe d more tha n 30 mg/kg NAS 1978). The u s ually highe r mercury con c entrati on s in fish-eating fu rbear ers than i n herbivo ro us



### 45spe c ie s seem ed to reflect t he amou nts o f fish and oth e r aqu atic o r g anism s in the diet. In river otter and min k from the Wi sconsi n River d r aina ge sy ste m , Hg levels parall e led tho s e re co rd ed i n fish, crayfish, and bottom sedim ents at that location. Highe st Hg l e vels in a ll sa mples we re reco rde d abo u t 30 km do wn strea m from an area that sup ported 1 6 pul p and pa per mills and a ch loral k ali pla n t; resid u e s we re highe st in the fur, followed by the liver, kidn ey, muscle, a nd br ai n (She ffy and St. Amant 1982 ).

In marine ma mmals, mo re than 90 % of the mercury content is ino r gani c; however, enou gh m e thylmercury occurs in sele cted tissue s to result in the accumula tio n of high tissue co ncentrat i ons of methy l mercury in human s an d wildlife con s u m ing su ch m eat (Cla rkson et al. 1984). The liver of the ringe d se al ( Pho ca hi spid a )

norm a lly cont ains 2 7 ,000 t o 187,00 0 ug Hg/kg fre s h wei ght, and is a traditional a nd com m on f ood of the co astal Inuit people (Eaton et al. 1980). Althou g h levels of Hg in hair (1 09,0 00 ug/kg) an d blood (3 7 ug/ l) of Inuits we re gro ssly elevat ed, no sympt o ms of Hg po isoni ng were evi dent in the coa s tal Inuits. Similar high con c entratio n s have bee n re ported fo r Alaskan Eskimo mo thers who, during p r e g n ancy, ate s e a l oil twice a d a y, and seal - meat or fish fro m the Yukon

- Ku sko k wim Coa s t every day (Galst e r197 6). Despite the extremely high total Hg content of seal liver, only the small organ ome r cury com pon e n t wa s a b sorbed an d app e a red in the tissue s. Cats fe d a diet of seal liver (2 6,000 u g Hg/kg fresh weig ht) fo r 90 days sh owed no neurologi c or hi stopath o logi c sig n s (Eaton et al. 1980 ). It seems that the to xic potential o f seal liver in term s of accu mulated tissu e levels in cats (up to 862 u g total Hg/l blood, and 7,60 0 ug total Hg/kg hair) is bett e r indi cated b ythe organo mercury fra c ti on in seal liver tha n by the con c entration of to tal Hg (Eaton et al. 1980).

Table 10 . Sublethal effect s of org anom ercury compo und s admini s tered to selected spe c ie s o f mammals.

Do se, and ot her Orga nism variable s Effect Referen c e

Rhe s u s mon k ey, 16 μg/kg b o d y No mea s u r a b l e Khera 1 979
Maca ca mulatta weig ht daily on eff ect on days 20 to 30 of rep r od uctio n
preg nan cy Huma n, adult 50 μg/day Risk of Clarkson

pare s the s ia, et al. 1984
0.3% (burnin g pricklin g se nsation of
ski n)
Huma n, adult 200 μg/day Risk of Clarkson

pare s the s ia, 8% et al. 1984 Cat, Felis 250 μg/kg bo dy Incre a sed Khera 1 979
dom esticus weig ht daily on incid e n c e of days 10 to 58 of anomal ou s
ges tation; oral route fetus e s Harp se al, 250 μg/kg bo dy Re sidu es of Ron a ld Pagophilu s weig ht daily for 47,200 to et al. 1977; groenla ndi cus 90 days; diet ary 82,500 μg/ k g Ramp ra sh ad

route fresh weig ht and Ronald 1 977 in liver, kidne y, and muscle; histo patholo g y



### 46of middle ea r Rat, Rattus sp. 500 μg/kg bo dy Red u ced Khera 1 979 weight daily; fertility
oral route
Huma n, adult 1,000 μg/day Risk of Clarkson et

pare s the s ia, 50% al. 1984 Mink, 1,100 μg/kg Re sidu es of Kuce ra 19 83
Must ela vi so n in diet 7,100 to 9,300 μg/kg
in brain; sign s of poi so ning
Rat 2,000 μg/kg Adverse Suzu ki 197 9 in diet (as behavio ral
P a cif i c blu e cha nge s in
marlin ); gesta tion offsprin g throug h po stnatal day 16
Rat 13,300 to Impaire d Wu et al. 50,000 μg/ k g cutan eou s 1985 body wei ght sen s itivity daily for 5 and he arin g days; up to one
sub c uta neo u s year po st- injectio n treatment Monkeys, Variou s Visual di sturb ances Suzu ki 197 9
Maca ca spp

. at blood Hg levels of 1,200 to 4,000 μg/L or brain Hg levels of 6,00 0 to 9,000 μg/kg; tremors at
blood Hg leve ls of 2,000 to 10,000 μg/L;
kidn ey pathol ogy at
brain Hg level s of 1,500 μg/kg
Huma n, adult Variou s Symptoms of Suzu ki 197 9 poisoning
evident at residue s of 1,200 μg Hg/L blood, 2,00 0 to 3,000 μg/kg whol e body

, or 3,400 μg/ k g hair



### 47Mice, Mus sp p. Variou s Re sidu es of Suzu ki 197 9 2,000 to 5,00 0 μg/kg hai r or >10,0 00 μg/kg brain

asso ciated wi th motor
inco ordi natio n and de crea se d
swim ming a b i lity; no
observabl e effect at

< 2 ,000 μg/k g hair
Huma n, infan t Variou s Severe effect s Elhassani at blood Hg 1983 levels of 3,00 0 μg/L

Retentio n of mercury by m a mmalia n tissues i s l ong er for org anom e r cu ry co mpou nds (espe c iall y methylmercu ry) than for ino r gani c me rcury compou nd s (NAS 1978; Clarkson a n d Marsh 198 2; Elhassani 1 9 83; Clarkson et al . 1984). Excretion of all Hg spe c ie s follo ws a compl e x, variable, mu lticompa rtme ntal pattern; the longe r-lived chemical Hg speci e s h a ve a biologi cal h a lf- life that ra nge s from ab out 1.7 days i n human lu ng to 1.36 years in whol e body o f various pin n i ped s.

OTHE R GR O U PS Methylmercu ry compou nd s have indu ce d abno rmal sex chro mo so mes in the fru i t fly ( D r os oph ila

m e lanoga ster ) (NAS 19 78; Khera 1 979 ). Earthwo r m s ( Eise nia foeti d

a ) expo se d to soil containi ng methylmercu ry concentrati ons of 5.0 mg Hg/k g--typical of s o il Hg levels ne ar ch loral k ali pla n ts--sho w ed a signifi cant re ductio n in the numbe r of se gments reg e n e ra ted afte r 1 2 wee k s, and contain ed 85 mg Hg/kg on a whol e body fresh weig ht basi s . Rege ne ration was n o r mal at soil Hg levels of 1.0 mg/kg, alth ough b ody bu rden s up to 27 mg/kg were re co rd ed. It was co nclu ded that soil contamin ated with met h ylmercury p o se d a gre a te r hazard to the pred ators of earth wo rms t han to the ea rthwo r m s (Be y er et al. 1985). Studies with a different spe c ie s of ea rthwo r m ( Oct o ch aetu s pattoni ) an d mercuric chlo rid e , demon strated a prog re ssiv e initial increa se in rep r od uctio n as soil mercury level s in cre a sed from 0.0 to the 60-day le thal level of 5.0 mg/kg (Abba si an d Soni 1983 ).

CU R R ENT R E COMME ND ATIO NS Propo se d me rcu r y criteria f o r the protecti on of sen s it ive aquati c org anism s, birds, and mamma ls, as well as human h ealth , are sh own i n Table 11. In almost eve ry in stance, these crite r ia are lis ted a s co nce n tration s of total Hg, with most, if not all, the Hg pre s ent as an o r g anome r cury speci e s.
In 1980, the U.S. Environmental Prote c tion Agen cy' s pro p o s ed m e rcury criteri a for fresh w ate raquati c life prote c tion we re 0.000 57 u g /l (24-hou r a v erage ), not to ex cee d 0.0 017 ug/l at an y time; these crite r ia seem ed to afford a high degree of pro t ection to fre s hwate rbi ota, as jud ged by survival, bio c oncentratio n , and biomag nificati on. Literature documente d in this pap e rsh o w e d that mercury con c entration s in water of 0.1 to 2.0 ug/l were fatal to sensitive aquati c sp eci e s an d that c oncentratio n s of 0.03 to 0.1 ug/l were a s so ciated with signifi cant su blethal effect s. The 198 0 prop osed fre s hwate r criteri a provide d sa fety factors fo r acute toxi cities of 175X to 3,50 8X base d on the 24-h o u ra v erage, an d 5 8 X to 1,176X based on the maximum pe rmissi ble

con c e n tration (Table 1 1 ). For p r ote c tion again s t su b l ethal effects, these value s were 5 3 X to 175X ba sed on the 24-h o u rmea n , and 18X to 59X base d o n the maximu m permi ssi bl e con c e n trati on (Ta b le 11 ). However, t he most current freshwater crit eria of 0.012 ug/l, not to exceed 2.4 ug/l (T abl e 11; EPA 1985), dramatically reduces the level of protection afforded aq uatic b i ota: safety fact ors for a c ut e toxicities are now 8X to 1 67X based o n the 96-h o u raverage, and o n ly 0.04X to 0.8X based o n the maximum permi ssible concentratio n . For protectio n again s t su ble t hal effects, these value s were 2X to 8X based o n the 4-d a y average, and o n ly 0.01X to 0.04X based on the maximum pe rmissi ble con c entration, o ressentially no significant protection.



### 48The proposed saltwater crit eria of EPA (1980) for m e rcury and mari ne life were unsatis factory. Proposed saltwater valu es of 0.025 u g /l (24-hou r a v erage ), not to ex cee d 3.7 ug/l at any time (Ta b le 11 ), provide d sa fety factors of 4X to 80X again s t acute toxicity (base d on 2 4 -ho u r ave r a ge), but less t han 0.5X ba sed on the maximum pe rmissi ble level

. For prote c tion agai nst su blet hal dam a ge effects, th e safety facto r s comp uted were 1.2X to 4X (base d on 24 -h our ave r ag e) and le ss tha n 0. 03X (ba s e d on maximu m allowa ble concentratio n ). The most recent saltwater cr iteria of 0.025 ug/l, not to exceed 2.1 ug/l (T able 11; EPA 1985), does not appear to offer a su bsta ntive incre a se in prote c tio n to marine lif e, when com pare d to crite r ia propo se d 5 years e a rli e r (EPA 1980). It seems that some downward modificati on is needed in the proposed Hg saltwater criteria if marin e and e s tuari ne biota are to be pro v ided even m i nimal protect i on.

Table 11. Propo sed me rcury crite r ia for protectio n of variou s re so u r ce s an d hum an health.

R e s o ur ce a n d c r iter io n Me rc u r y (units in p a re ntheses) con c e n tration Referen c e

Aqua tic life

Freshwater Total recoverable Hg EPA 1980 (μg/L) <0.00 057 (24 h

averag e), not to

excee d 0.001 7 at any
t i m e <0.012, 4-day average EPA 1985 (not to be exceede d

more tha n on ce every 3 years; <2.4, one-h o u r
averag e (n ot to be

excee ded mo re than on ce

every 3 years) a
Saltwater Total recoverable Hg EPA 1980 (μg/L) <0.02 5 (24 h

averag e), not to

excee d 3.7 at any time <0.025, 4-day average EPA 1985 (not to be exceede d

more tha n on ce every 3 years); <2. 1

, one-h o u r
averag e (n ot to be

excee ded mo re than on ce

every 3 years) a

Fre s h w ater (μg/L)
Inland surfa c e <10.0 from p o int sou r ce Abbasi a nd waters, India discha rge Soni 1983

Fish (μ g/kg fresh weig ht)
Brook trout, Salvelinu s fontinali s



### 49Whol e body <5,000 EPA 1980, 1985
Wildlife
Birds
Tissue resi du es (μg/kg fresh weig ht)
Feathe r <5,00 0 NAS 1978
E g g M a l l a r d

, Anas platyrh y

n c ho s <90 0 Hein z 19 79 Ring -ne c ked phea sa nt,
Phasianu s colchi cu s <90 0 Spann et al. 1972
Variou s spe c i e s 1,300– 2,000 Fimreite 19 79 Diet (μg/kg fresh weig ht) 50 to <10 0 Hein z 19 79;
March et al. 1983 Daily do se (μ g/kg bo dy weig ht) <64 0 Spann et al. 1972;
McEwen et al

. 1973;
Mullins et al. 1977
Mammal s

Tissue resi du es (μg/ kg
fresh weig ht) Kidney <1,100 EPA 1980
Blood <1,20 0 Suzu ki 197 9
Brain <1,50 0 Suzu ki 197 9
Hair <2,00 0 Suzu ki 197 9 Diet (μg/kg fresh weig ht) <1,10 0 Kuce ra 19 79 Daily do sage (μg/kg body wei ght) <25 0 Ramp ra sh ad and
R o n a l d 1 9 7 7 ; Ron a ld et al. 1977;
Khera 1 979
Hum a n Healt h
Tissue resi du es

(μg/kg fresh weig ht)
Blo o d < 2 00 G a ls ter 1 9 76
Hair <6,00 0 Lode niu s et al. 1983
Wate r (μg/L )
Potable <2.0 NAS 1978
Protec tion from toxic

prop ertie s of Hg thro ugh

con s um ption of
contami nated aquatic organisms <0.146 EPA 1980



### 50Protec tion from toxic

prop ertie s of Hg from inge stion of water plus con s um ption of
resi dent aq ua tic organisms <0.144 EPA 1980

Fish an d se afood
Acce ptable in take (μg ) Daily, 60 kg a dult 25 Khera 1 979
Wee k ly, 70 kg adult 200 Khera 1 979
Wee k ly, adult 500 Lode niu s et al. 1983 Pregn ant wo men (μg/kg fresh weig ht) <25 0 Khera 1 979
Variou s lo cati ons (μg/kg fresh weig ht) Jap a n <40 0 NAS 1978
Can ada, West Germany,
U.S.A. <50 0 NAS 1978
Australi a <50 0 (me an), not
to exceed 1,5 00
in any sampl e Lyle 1984
Finland <1,00 0 Lode niu s et al. 1983
Scandin a via <1,00 0 Suckch aroen and
Lode niu s 198 3
Swede n <1,00 0 NAS 1978
U.S.A. <1,000 EPA 1980, 1985;
Barbe r et al. 1984;
Miller and Jude 1984
Food s of ani mal origi n (μg/kg fresh weig ht)

Livesto ck tissues <50 0 Best et al. 1981
Wildlife tissue s <50 Krynski et al. 1982
B r e a s t m u s c l e Dome stic p o u l try <50 0 NAS 1978
Du cks (wildlif e) <1,00 0 Lind say and
D i m m i c k 1 9 8 3
All foods
Adult week ly intak e (μg)
As total Hg <15 0 NAS 1978
As methylmercury <10 0 NAS 1978
Variou s lo cati ons (μg/kg fresh weig ht)
Australi a 10 to 100 NAS 1978



### 51Benelux co un tries <30 NAS 1978
Brazil <50 NAS 1978
Can ada <50 0 Bodaly et al. 1984
U.S.A. <1,00 0 Bodaly et al. 1984

a All mercury that passe s th roug h a 0.45

- mm memb ra ne filter after the sam p le is acidifie d to pH 1.5 to 2.0 with nitric ac id.

The sig n ifica n ce of elevat ed Hg resi du es in tiss ue s of aquatic o r g anism s is n o t fully understo od. Con c e n tratio ns >1,000 u g Hg/kg fre s h weight ca n occu r in vario u s t i ssue s of sele cted spe c ie s of fish and aquati c mam m als eate n b yhumans. But it would be incorr e c t to assume that a quatic foo d chain s --e s pe ci ally marin e food chain s --in corp orate Hg excl usively from anthro pog eni c activities (Barbe r et al. 1984). Some orga nisms, h o weve r, do contain Hg tissue re sidu es a s so ci ated wit h kno w n a d verse effect s to the orga nism and its pred ators. Thus, whole body re sidu e s of 5,000 to 7,000 ug Hg/ k g fre s h weig ht in broo k tro u t eventually proved fatal to that species (EPA 1980 ). To protect sensitive speci e s of mamm als and bi rds that regul arly

con s um e fish and other a q uatic organi sms, total mercury con c ent rations in the s e food items sho u ld proba bly not

excee d 100 u g /kg for avian protectio n , or 1,100 ug/kg fo r sm all mam m als (Table 1 1 ). By comp arison, propo sed Hg level s in fish an d se afo od, in ug/kg fresh weig h t, for hum an he alth prote c tio n sho u ld not excee d 250 f o r expecta nt mothers, a nd 40 0 to 1,000 for adults world w ide (Tabl e 1 1 ).

Since lon g -liv ed, slo w -g ro wing, hig h -tro phic-po siton aquati c org a n i sms u s u a lly contai n the hi ghe st tissu e mercury resi d ues, some fisherie s ma nag ers h a ve prop os e d a legal maximum limi t based o n fish length or b o d y weig ht, or alternatively, co nstrai ning the mean Hg co nce n tr ation ofthe entire cat c h to a nomin ated level. In the Australi an sh ark fi she r y, for example, im plementatio n of a maximum length re striction (to a no minated level of 500 ug Hg/kg ) , would re sul t in retention of less tha n h a lf of the present catch of seven sp eci e s (Lyle 198 4).
Among sen s itive avian spe c ie s, adv erse effects--p red o minantly on re p r od uctio n --have be en reporte d at mercury con c entration s (i n ug/kg fresh weight) of 5,00 0 in feather, 9 00 in egg, 50 to 100 in diet, and daily admini s tered doses of 64 0 on a body we ight basi s (T a b le 11). Although lo w Hg con c e n tration s --e.g., 50 ug /kg in the diets ofdomesti c chi c ken s --somet i mes p r od uce d no adverse effects on chi c ken s , the tissue resi due s of Hg were sufficiently elevat ed to pose a hazard to hu man co nsum ers (Ma r ch et al. 1983). In contrast, in e ggs of the American bald eagl e (with 150 u g Hg/kg an d low hatch ), other contami nant s present--e s p e cially orga no chlo rin e comp oun ds--p rob ably ha d a greate ref fect on hatch ability than did Hg (Wiem e yer et al. 1984).

Mammal s , su ch a s the do mestic cat an d the harp se al, sho w ed bi rth defe c ts, hi stopath o logy, and elevated tissu e re sidu es at do se s o f250 ug Hg/ k g body wei g h t daily (Table 11). The min k , at dietary levels of 1,10 0 ug Hg/kg, had si gns of me rcury poisoni ng; Hg re sid u e s in mink b r ain at this dietarylevel range d from 7,100 to 9,300 ug/ kg (Kuce r a 19 83). Tissue resi due s in kid n e y , blood, brai n, and hair in exce ss of 1,1 00 ug Hg/kg i n other no nhu man mamm al s are u s u a lly con s id ere d presum pt ive eviden ce of sig n i ficant Hg con t amination (T able 11).

At this point, it seem s that four cou r ses o faction ar e warranted. First, toxic mercurial s in ag riculture an d indu stry sho u l d be repl ace d by less toxi c su bstitute s. Sec ond, cont rols sho u ld b e applie d at the point of ori g in to prevent the di scharge of po t entially harm f ul Hg wa ste s . Third, conti nued p e rio d ic monitorin g of fishery and wildlife re so urce s is impo rt ant, espe ciall yin areas wi th potential for rese rvoir d e velopme n t, in light of the hypothe sis th at incre a sed floodin g incre a se s the avail abilit y of Hg to biota. And finally, additional re sea r ch i s need ed on m e rcury a c cum u lation an d d e toxication in comp aratively pristine e c o s ystem s

.



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Figure 1. Major tran sfo r ma tions of mercury in the environm ent (mo d ified from Beijer an d Je rn elov 1979 ).



### 62Figure 2. Mercu r y co ncent ration s in livers of four spe c ie s of pinnip ed mammal s (from Eisl er 1 984).



### 63