Factors influencing blood mercury levels of inhabitants living near fishing areas

6 Pages·0.636 MB·English

by  Lee C.-C., Chang J.-W., Huang H.-Yi, Chen H.-L. et al.

ScienceoftheTotalEnvironment424(2012)316–321
ContentslistsavailableatSciVerseScienceDirect
Science of the Total Environment
journal homepage: www.elsevier.com/locate/scitotenv
Factors influencing blood mercury levels of inhabitants living near fishing areas☆,☆☆
Ching-Chang Lee b,c, Jung-Wei Chang b, Hsin-Yi Huang b, Hsiu-Ling Chen a,⁎
aInstituteofOccupationalSafetyandHazardPrevention,HungKuangUniversity,Taichung,Taiwan
bDepartmentofEnvironmentalandOccupationalHealth,MedicalCollege,NationalChengKungUniversity,Tainan,Taiwan
cEnvironmentalTraceToxicSubstancesResearchCenter,MedicalCollege,NationalChengKungUniversity,Tainan,Taiwan
a r t i c l e i n f o a b s t r a c t
Articlehistory: Methylmercury(MeHg),awell-knownneuro-toxicant,isusuallyemittedbyindustrialandotherman-made
Received3November2011 activities;itisingestedwithseafoodandshellfish,andaccumulatesinthehumanbody.Theaimofthisstudy
Receivedinrevisedform3January2012 wastocomparethedifferencesinbloodlevelsoftotalmercury(T-Hg)andMeHginresidentsof4coastal
Accepted23January2012 sites and 4 inland sites around Taiwan. Meanwhile, the potential question is warranted to find out the
Availableonline22March2012
association between dietary intake and MeHg accumulation. We found that coastal residents had
significantlyhighermeanbloodT-Hglevels(mean:16.1μg/L,range:0.9–184.9μg/L)thaninlandresidents
Keywords:
(mean: 11.8μg/L, range:0.8–146.6μg/L). Thesame was for blood MeHg levels: coastal residents (mean:
Totalmercury
Methylmercury 16.5μg/L,range:0.9–184.9μg/L),inlandresidents(mean:11.8μg/L,range:2.1–133.4μg/L).Theseelevated
Blood levels were positively associated with seafood and shellfish consumption. However, the nature of their
Coastalandinlandinhabitants residentialareamayalsobeanimportantfactor,becausethehighestT-HgandMeHglevelswerefoundin
Fishconsumption residentsofarelativelynon-industrializedarea.Toprotectvulnerablepopulation—especiallychildrenand
Industrialpollution pregnantwomen—itisimportanttoknowwhetherlocallycaughtorraisedandconsumedfishhasanysource
ofHgandMeHgpollution.
©2012ElsevierB.V.Allrightsreserved.
1.Introduction comefrommainlandChina(Fangetal.,2009).Therefore,bothlocal
industrialemissionsandoverseassourcesofHgpollutionaresignifi-
Mercury (Hg) occurs naturally and because of human activities. cantcontributorstoTaiwan'senvironmentalHgcontamination.
OneprimarychemicalformofHgismethylmercury(MeHg),awell- ThemeanbloodHgconcentrationinCambodianswas5.2–58μg/L,
known neurotoxin. Approximately 300,000 personal computers are lowerthanthoseinHg-contaminatedorhighfish-intakeregions,but
disposed of every year in Taiwan. The Hg contained in these higherthanthoseinnon-contaminatedregions(Agusaetal.,2007).
computersmaycontaminatetheenvironmentiftheyarenotproperly HgaccumulationwasestimatedbasedontheHgcontentinfishand
disposedof(Leeetal.,2000).Moreattentionshouldbepaidtohow on the daily fish consumption by women of childbearing age and
thecurrentcomputerrecyclingsysteminTaiwancontributestoHg pregnant women because Hg might be transferred to the fetus via
pollutionofthelocalenvironment. cord blood or to the newborn via breastfeeding (Bjönberg et al.,
There is considerable Hg pollution in northern Taiwan; this is 2005). For example, Hg levels decrease during lactation, which is
primarily anthropogenic contamination, and re-emission may exist probablyattributabletoitsbeingexcretedinmother'smilk(Vahter
because of Hg contamination in soil surfaces (Kuo et al., 2006). In etal.,2000).InTaiwan,21.6%–24.3%and45.6%–57.4%oftheestimat-
southern Taiwan, a cross-sectional study (Chang et al., 2008) eddailyHgdosesinthosewhoconsumetypicalandlargequantities
reportedthatelevatedbloodtotal-mercury(T-Hg)andMeHglevels ofseafood,basedontheMonteCarlosimulation(Chienetal.,2007),
in 240 adults living near a deserted chloralkali plant had polluted exceedtheUSEPA'sreferencedose(0.1μg/kg/day).However,inother
the environment with a substantial amount of Hg 20years before. cases,extremelyhighHgaccumulationinspecificpopulationscannot
Both studies showed that Hg contamination has occasionally beexplainedbyfishconsumption,whichindicatesthatsomeother
occurred in Taiwan. The atmospheric Hg detectable in Taiwan may source of Hg contamination exists (Agusa et al., 2005). Meanwhile,
in addition to the fact that fish consumption might be the major
☆ Interestdeclaration:Allauthorsdeclarethattheyhavenocompetinginterests. source, age and racial/ethnic differences were also noted as factors
☆☆ Ethicalconsideration:ThestudyprotocolwasapprovedbytheHumanExperi- affectinglevelofHgcontamination(Caldwelletal.,2009).
mentandEthicsCommitteeofNationalChengKungUniversityMedicalCenter.The AtmosphericHgsamplinginurban,suburban,rural,andindustrial
participantsprovidedwritteninformedconsent. areashasshownthatthehighestlevelwas30ng/m3inurbansites,
⁎ Correspondingauthorat:InstituteofOccupationalSafetyandHazardPrevention, upto22ng/m3inruralsites,upto24ng/m3inindustrialsites,and
Hung Kuang University, 34 Chung Chie Road, Sha Lu, Taichung 433, Taiwan. Tel.:
up to 90ng/m3 in suburban sites in Taiwan (Kuo et al., 2006). In
[phone]x4010;fax:[phone].
E-mailaddress:[email protected](H.-L.Chen). addition,thereisconsiderableatmosphericHginspecialareas,such
0048-9697/$–seefrontmatter©2012ElsevierB.V.Allrightsreserved.
doi:10.1016/j.scitotenv.2012.01.049
C.-C.Leeetal./ScienceoftheTotalEnvironment424(2012)316–321 317
asminingareas(Fangetal.,2009),andlocalHgsourcesneedtobe 2.4.MeasuringqualitycontrolandqualityassuranceforT-HgandMeHg
investigated.
TheprimarypublichealthconcernisrelatedtoMeHgexposure. Eachanalyticalrunconsistedofamethodblank,aqualitycontrol,
MeHg ingested and bio-accumulated with seafood, shellfish, and andsixunknownsamplesforqualityassuranceandqualitycontrol.
freshwater fish have not been systematically investigated, even Dataqualitywascontrolledandassuredbyspikingknownamounts
though fish and other marine foods are popular and frequently ofT-HgandMeHgintobloodsamplesbeforeanalyzingtheblood.A
eaten in Taiwan. Therefore, to identify regional Hg contamination reference material, Standard Reference Materials 966 Toxic Metals
levels,weinvestigatedthebloodHgandMeHglevelsinpeopleliving inBovineBlood(SRM966)(NationalInstituteofStandardsTechnol-
in4coastalsitesand4inlandsitesaroundTaiwan.Wehaveincluded ogy, NIST) was used for quality assurance of T-Hg; the measured
information about fish consumption and general dietary habits concentration met the certified values (29.7–33.1μg/L).The method
to evaluate the association between dietary intake and MeHg detection limits of T-Hg and MeHg were 0.09 and 0.144μg/L,
accumulation. respectively.
2.Materialsandmethods
2.5.Interviewer-administeredquestionnaire
2.1.Participantselection
Each participant was asked to fill out a questionnaire about
personal characteristics (gender, age, height, weight, occupational
We chose eight locations around Taiwan to measure the blood
history, neighborhood geography, pregnancy history, etc.), lifestyle
T-HgandMeHglevelsinresidents:TaipeiCounty(north),Changhua
(alcohol consumption and smoking habit), and dietary intake for
County (west central), Kaohsiung City (south), and Yilan County
the previous year based on a semi-quantitative food-frequency
(east). In each location, one coastal and one inland townor village
questionnaire.Fishandotherseafoodwerethemajoritemsthatwe
wereselected.Theinclusioncriteriaforstudyparticipantswerethat
selected for assessing the association between blood MeHg levels
they were between 18 and 65years old and that they had lived in
andconsumptionquantity.Thefishitemwasgroupedaslarge-sized
the selected area for a minimum of 5years. Each study participant
remoteseafish,small-sizedremoteseafish,small-sizedoffshoresea
provided 20mL of venous blood after signing an informed consent
fish,fish-farmfish,freshwaterfish,shrimp,shellfish,oysters,andoc-
form, which, along with the study protocol, had been approved by
topus.Theintakefrequenciesonthequestionnairewere:3times/day,
the Human Experiment and Ethics Committee of National Cheng
1–2times/day,4–6times/week,1–3times/week,1–3times/month,
KungUniversityMedicalCenter.Theparticipantswereaskedtofast
1–11times/year,andnever.Consumedquantitiespermealforeach
overnight before blood sampling. Blood samples were drawn into
food type were then estimated. Quantitative data for intake of fish
chemically clean tubes containing anticoagulants, and part of the
andotherseafoodwerecalculatedbasedonbowls(200g)foreach
serum samples was obtained after the blood had been centrifuged
forbiochemicalanalysis.Bloodsampleswerestoredat−20°Cuntil food items. The questionnaires were administered by our trained
interviewersaccordingtostandardoperatingprocedures.
T-Hg and MeHg analysis. First, we recruited 565 participants for
T-Hg analysis, and the following, 249 of those participants were
selectedforMeHganalysisbasedontheyeatmorefishandseafood
thanotherpeople.
Table1
Demographiccharacteristicsofthestudysubjects.
2.2.BloodT-Hganalysis
Coastalsites Inlandsites P-value
N= 262 303
T-Hg was analyzed with fully-automatic heat vaporization
Sexa
mercury-measuring equipment (MA-2000; Nippon Instruments Men 127(48.5%) 150(49.5%) 0.866
Corporation, Tokyo, Japan) using a method that complied with US Women 136(51.3%) 153(50.5%)
EPA 7473 and American Society For Testing and Materials (ASTM) Ageb 43.4(17.0–69.0) 43.9(18.0–74.0) 0.749
D6722-01.HeatvaporizationliberatesHg,whichiscollectedasgold BMIb 24.7(16.0–48.3) 24.6(16.4–40.9) 0.821
Bodylipid
amalgamandthenmeasured.Afterthegoldamalgamisheated,Hg Menb 23.6(8.3–34.5) 24.2(9.8–35.0) 0.344
atomsemitted,andtheirintensityisdetectedusingcoldvaporatomic Womenb 31.9(21.2–63.2) 31.4(17.1–43.9) 0.599
fluorescencespectrometry(CVAFS)atawavelengthof253.7nm.To Occupationc
limitinterference,thevaporwasdehumidifiedusingagaswash. Agriculture 14(5.4%) 19(6.3%) b.0001⁎
Fishery 14(5.4%) 1(0.3%)
Livestockbreeding 4(1.5%) 0(0%)
2.3.BloodMeHganalysis Bluecollar 12(4.6%) 17(5.6%)
Business 8(3.1%) 23(7.6%)
Service 38(14.6%) 69(22.5%)
The blood sample analysis procedures used in this study were
Publicaffairs 75(28.7%) 38(12.5%)
modifiedfromthosereportedbyVázquezetal.(1999).First,2.5mL Others 74(28.4%) 112(36.9%)
blood was placed in a Teflon-lined tube and then toluene (15mL) Residentperiodb 29.8(0.25–69) 28.9(0.33–75) 0.585
wasaddedformicrowavedigestion.Themicrowaveextractionwas Smokingstatusc
Smoker 77(29.7%) 79(26.1%) 0.373
done at 100°C with 100% power (Microwave Accelerated Reaction
Passivesmokers 170(65.1%) 183(60.0%) 0.258
System[MARS];CEMCorp.,Matthews,NC).Aftertheextractionhad Smokingyear(year)a 18.8 20.9 0.116
beencompletedandthesupernatantcooledtoroomtemperature,it Alcoholusagec
was cleaned using 3mL of a 1% aqueous cysteine acetate solution. Drinker 52(20.2%) 75(24.8%) 0.225
Finally, 1mL of the toluene extract dried over anhydrous sodium Drinkingperiod 19.6 21.7 0.249
Drinkingquality 2.0 1.9 0.613
sulfate was analyzed using a gas chromatograph (6890; Hewlett-
PackardCompany,PaloAlto,CA)equippedwithanelectroncapture Note:Inparenthesesarerangesorpercentages.
a TestedbyFisher'sExactTest.
detector and an Ulbon HR-thermon-Hg capillary column (15m
b TestedbyWilcoxonRankSumsTest.
long,0.53mm internal diameter)(ShinwaChemical IndustriesLtd., c TestbyChiSquareTest.
Kyoto,Japan). ⁎ P-valueb0.05.
318 C.-C.Leeetal./ScienceoftheTotalEnvironment424(2012)316–321
160 2.6.Statisticalanalysis
mL)140 MeHg level=1.304+0.786*T-Hg level; r2 = 0.956; T-HgandMeHgconcentrationsarereportedasμg/L.JMP(version5.0;
n (ng/120 p<0.0001, dotted line were 95% confident interval SwAeSreInsutsietudtef,oCrarsyta,NtisCt)icaanldaSntaaltyisstisic.aT(hveerpsiaornti7ci.p1;anSttastSwoeftr,eIndc.i,vTiduelsda,iOnKto)
atio100 coastalandinlandresidentgroups.Fisher'sexacttestoraχ2testwas
ntr used to comparethe demographic data between the two groups, and
ce 80 theWilcoxonSigned-RanktestandKruskalWallistestwereusedtocom-
n
o paretheT-HgandMeHglevelsbetweenparticipantslivingindifferent
d c 60 areas.Inaddition,afteranadjustmentforageandotherfactors,simple
o
blo 40 andmultivariateregressionanalyseswereusedtoexaminetheassocia-
g tionbetweenbloodMeHglevelandtotalseafoodandfishconsumption.
H
e 20
M
0 3.Results
0 20 40 60 80 100 120 140 160 180 200
T-Hg blood concentration (ng/mL)
3.1.Demographiccharacteristicsofsubjects
Fig. 1. The association between total blood mercury (T-Hg) and methylmercury
(MeHg) concentrations. MeHg level=1.304+0.786; *T-Hg level; r2=0.956; The gender ratios, age, BMI, body lipid levels, duration of resi-
pb0.0001,dottedlinesarethe95%confidenceinterval. dence, smoking status, and alcohol intake of the inhabitants were
not statistically different between coastal and inland sites (Pb0.05,
Table1).Thereweremorefishermenincoastalsites(5.4%)thanin
inlandsites(0.3%).
CN
T-Hg: 10.2 ng/mL
MeHg: 8.8 ng/mL
RN
T-Hg: 7.9 ng/mL CE
MeHg: 6.7 ng/mL T-Hg: 26.1ng/mL
MeHg: 25.1 ng/mL
RE
T-Hg: 18.7ng/mL
RC MeHg: 18.2ng/mL
T-Hg:8.0ng/mL
MeHg:7.3ng/mL
CC
T-Hg:6.9ng/mL
MeHg:6.1ng/mL
RS
T-Hg:12.3ng/mL
MeHg:12.8 ng/mL
CS
T-Hg:21.7ng/mL
MeHg:22.0ng/mL
Fig.2.T-HgandMeHgbloodconcentrationsinTaiwanese.
C.-C.Leeetal./ScienceoftheTotalEnvironment424(2012)316–321 319
Table2
DifferenceofbloodT-HgandMeHglevelsamongtheinhabitantlivingnearcoastalandinlandsites.
Areas Total North Center South East P-value
Coastalsites T-Hg(μg/L) N=262 N=70 N=59 N=59 N=68 b.0001⁎,a
16.2±17.6 10.2±5.1 6.9±3.7 21.7±26.7 26.1±17.4
(0.9–184.9) (0.9–30.8) (1.8–16.3) (2.5–184.9) (5.0–91.1)
Inlandsites T-Hg(μg/L) N=303 N=71 N=84 N=68 N=80 b.0001⁎,a
11.8±12.1 7.9±4.3 8.0±3.9 12.3±18.0 18.7±13.1
(0.8–146.6) (0.8–20.2) (2.0–18.3) (2.7–146.6) (1.1–73.4)
P-value b0.001* 0.003* 0.105 b0.001* 0.004*
Coastalsites MeHg(μg/L) N=111 N=28 N=22 N=25 N=36 b.0001⁎,a
16.5±18.1 8.8±3.4 6.1±3.5 22.0±26.7 25.1±16.6
(2.3–137.8) (3.7–16.4) (2.3–14.9) (3.1–137.8) (5.5–60.6)
Inlandsites MeHg(μg/L) N=138 N=33 N=31 N=31 N=43 b.0001⁎,a
11.8±12.1 6.7±3.1 7.3±3.5 12.8±23.0 18.2±13.4
(2.1–133.4) (2.1–14.8) (2.4–16.2) (2.1–133.4) (3.1–66.1)
⁎ ⁎ ⁎ ⁎
P-value 0.010 0.018 0.194 0.028 0.036
Note:thedatameantmean±standarddeviationandinparenthesesarerangesorpercentages.
a TestbyKruskal–WallisTestamonginhabitantlivingindifferentareas.
⁎ P-valueb0.05.
3.2.Serumconcentrationsoftheparticipants 3.3.Hgexposureandfoodintake
BloodT-HgandMeHglevelsweresignificantlycorrelatedinour 3.3.1.Sourceoffoodanddietaryintake
participants (Fig. 1). Mean blood T-Hg levels (coastal site mean: Lessthan1%oftheinhabitantswerevegetariansin coastalsites
16.1μg/L, range: 0.9–184.9μg/L versus inland site mean: 11.8μg/L, and b3.3% in inland sites (Table 4). In coastal sites, 90.1% of the
range:0.8–146.6μg/L)andMeHglevels(coastalsitemean:16.5μg/L, participantsreportedthatthefishtheyatewaspurchasedinmarkets,
range: 0.9–184.9μg/L versus inland site mean: 11.8μg/L, range: 29.4%fromcatchingfish,and8.4%ofthefishwascultivated,aswellas
2.1–133.4μg/L) were significantly higher in coastal sites (Table 2). 96.7%,6.0%and0.7%,respectively,ininlandsites.Coastalresidentsate
Geographically,bloodT-HgandMeHglevelsweresignificantlyhigher small-sizedoffshoreseafish,shrimp,oyster,andoctopussignificantly
in eastern and southern sites thanin the northern and central sites. morefrequentlythandidinlandresidents(Table5).
The blood Hg levels were further grouped into fishermen and
non-fishermen(Table3).FishermenhadsignificantlyhigherT-Hgand 3.3.2.AssociationbetweenseafoodintakeandbloodMeHg
MeHglevelsthandidnon-fishermenineasternandsouthernTaiwan, SignificantlypositivecorrelationswerefoundbetweenMeHgand
butnotinnorthernandcentralTaiwan.InTaiwan,Hgaccumulation age,intakeoflarge-sizedremoteseafish,small-sizedremoteseafish,
in52.9%ofTaiwan'swomenofchildbearingageexceedstheUSEPA shrimp, crab, and octopus, respectively (Pb0.05, Table 6). Multiple
referencedose(Chienetal.,2010).Inthepresentstudy,theaverage linear regressions also showed positive associations for fish intake,
bloodT-Hglevelinourparticipants(13.8μg/L)wassignificantlyhigher age,andwheretheparticipantslived.
than blood T-Hg levels in 40 women sensitive to amalgam fillings Inthepresentstudy,bloodT-HgandMeHglevelswerehigherin
(median: 2.35μg/L) and in 43 non-sensitive controls (median: residents of eastern and southern Taiwan than of northern and
2.40μg/L) (Zimmer et al., 2002), than in 2369 Koreans 18years old central Taiwan, and higher in fishermen than in non-fishermen. In
andolder(mean:3.80μg/L)(Sonetal.,2009),andthantheindirectly Sweden,theintakedoseof4μgMeHg/kgbodyweight/dayestimated
exposed residents of a gold-mining area (Cortes-Maramba et al., fromfishintakerecordscorrespondedtobloodHglevelshigherthan
2006).Anotherstudy(ZhangandWong,2007)showedthatmainland 300ng/g(Skerfving,1974).About30yearsaftertheoutbreakofMin-
Chinesemenwhoatefishformorethan4mealsperweektendedto amatadisease,T-Hglevelsintheredbloodcellsofmaleresidentsof
havemoreHgintheirhair(ZhangandWong,2007).Overall,industrial the coastal area near Minamata City, especially in fisherman, were
pollutionandfishconsumptionappeartobethetwolargestsourcesof still significantly higher than those in male residents of the inland
anthropogenicHgaccumulationinhumans. area (Sakamoto et al., 1991). A cross-sectional study in Spain
Table3
DifferenceofbloodT-HgandMeHglevelsamongfishermanandnon-fishermenlivingaroundTaiwan.
Groups North Center South East Total
Fisherman T-Hg(μg/L) N=2 N=25 N=24 N=23 N=74
8.9 7.0±3.6 27.4±35.7 33.6±21.4 21.9±26.0
(4.6–13.2) (1.9–16.7) (3.4–184.9) (10.3–91.1) (1.9–184.9)
Non-fishermen T-Hg(μg/L) N=141 N=103 N=95 N=125 N=464
9.1±4.9 8.05±4.0 14.2±18.6 20.0±13.3 12.8±12.3
(0.8–30.8) (1.8–18.3) (2.5–146.6) (1.1–73.4) (0.8–146.6)
P-value – 0.327 b0.001⁎ 0.002⁎ b0.001⁎
Fisherman MeHg(μg/L) N=8 N=8 N=11 N=27
5.4±3.0 33.2±43.8 36.6±19.4 26.4±29.3
– (2.3–11.5) (3.3–137.8) (10.1–60.6) (2.3–137.8)
Non-fishermen MeHg(μg/L) N=59 N=39 N=45 N=68 N=211
7.7±3.4 7.3±3.7 14.7±20.9 18.9±13.1 12.7±13.3
(2.1–16.4) (2.3–16.2) (2.1–133.4) (3.1–66.1) (2.1–133.4)
P-value – 0.246 0.096⁎ 0.01⁎ 0.027⁎
Note:thedatameantmean±standarddeviationandinparenthesesarerangesorpercentages.
–:Datanotavailable.
⁎ P-valueb0.05.
320 C.-C.Leeetal./ScienceoftheTotalEnvironment424(2012)316–321
Table4 Table6
Dietarysourceanddietaryhabitsbetweentheinhabitantlivingnearcoastalandinland Simpleandmultiplelinearregressionanalysisofend-points.
sites.
Models r R2 P-value
Source Coastalsites Inlandsites P-value
LogMeHgversusage 0.335 b0.001*
(N=262) (N=303)
LogMeHgversusLoglarge-sizedremoteseafish 0.326 b0.001*
Foodtype LogMeHgversusLogsmall-sizedremoteseafish 0.205 0.002*
Vegetarian 2(0.8%) 10(3.3%) 0.043⁎ LogMeHgversusLogcultivatedfish 0.114 0.112
Carnivorous 260(99.2%) 293(96.7%) LogMeHgversusfreshwaterfish −0.085 0.215
Sourceoffish LogMeHgversusLogshrimp 0.220 0.001*
Cultivated 22(8.4%) 2(0.7%) b.0001⁎ LogMeHgversusLogcrab 0.273 b0.001*
Fishing 77(29.4%) 18(6.0%) b.0001⁎ LogMeHgversusLogshellfish 0.115 0.114
Purchased 236(90.1%) 289(96.7%) 0.002⁎ LogMeHgversusLogoyster −0.054 0.454
Unknown 16(6.1%) 20(6.7%) 0.864 LogMeHgversusLogoctopus 0.181 0.007*
Sourceofotherseafood LogMeHgversusfishintakeandage 0.280 b0.001*
Cultivated 16(6.1%) 0(0%) --- LogMeHgversusfishintake,ageandwhether 0.294 b0.001*
Fishing 41(16.7%) 1(0.3%) b.0001⁎ livingincoastalorinlandareas
Purchased 238(90.8%) 279(93.3%) 0.345 LogMeHgversusfishintake,ageandlocations 0.447 b0.001*
unknown 7(2.7%) 14(4.7%) 0.267 ofwheretheylivedinTaiwan
Note:thedatameantnumberofstudysubjectsandinparenthesesarepercentages, Note:Thefoodintakequantity(gram)wasusedforeachmodel.
TestbyFisher'sExactTest ⁎ P-valueb0.05.
⁎ P-valueb0.05.
(Passos et al., 2007) reportedthattheaveragebloodT-Hglevelwas terrestrialbiota,suchasfungi,plants,earthworms,snails,crabs,in-
38.6±21.7μg/L, and the average MeHglevel was33.6±19.4μg/L in sects, amphibians, lizards, snakes, and bats, in southern Taiwan,
studyparticipantswhoate7.4fishmealsperweek,morefishmeals which indicated significant industrial pollution of the environment.
thaneatenbytheTaiwaneseinthepresentstudy(3.88meals);their However, it is surprising that the highest T-Hg and MeHg levels
bloodT-HgandMeHglevelswerealsohigherthanthoseinourstudy. werefoundineasternTaiwan,whichistheleastindustrializedpor-
In contrast, the average blood MeHg level (median 1.7μg/L; range tionoftheisland.Ananalysisofheavymetalsinthefluegasfrommu-
0.30–14μg/L)in 127 Swedish women of childbearing agewhoatea nicipalsolidwasteincineratorsinTaiwan(Yuanetal.,2005)found
greatdealofvarioustypesoffish(about4meals/week)was(median that the removal efficiency of the air pollution control devices for
9.2μg/L;range2.1–137.8μg/L)lowerthaninourparticipantswhoate Pb,Cd,Zn,Cu,andCrwashigherthan90%,but thatformercuryit
fishalmostasfrequently.Theabovedatapointoutthatdespitesimilar was significantly lower because Hg appeared mainly in the gas
levelsoffishconsumptionbydifferentgroupsofpeople,bloodT-Hgor phase. Others have reported significant anthropogenic Hg emission
MeHglevelsareinfluencedbylocalpollutionsources(Fig.2). insouthandeastAsiafromthedevelopmentofelectricalandelec-
ChenandChen(2006)reportedthatthehighestHglevelswerein tronicmanufacturingindustries(Wongetal.,2006),smeltingfacili-
marinefish,especiallyintuna,andtheninshellfishandfreshwater ties (Cortes-Maramba et al., 2006; Fu et al., 2009), and mining
fish in Taiwan. Elevated T-Hg levels in the cord blood of newborns activitiesandwaste-disposalsites(Horvatetal.,2003).Taiwanwas
havebeenassociatedwithmaternalfishintake,particularlyoflarge, the major producer of large-sized liquid-crystal display television
oilyfishspecies(Ramóetal.,2008).Therefore,thequestionnairein- panels (LCD-TV), accounting for 34.7% of the worldwide market
terviewhasbeensetthatallfishwasgroupedintolarge-sizedremote (Tseng et al., 2007; Wang et al., 2007). This suggested that some
seafish,small-sizedremoteseafish,small-sizedoffshoreseafish,cul- localareasmightbecontaminatedwithHgbecauseoflocalmining
tivatedfishandothers.Wealsofoundthatlarge-sizedremoteseafish operations or the disposal of personal computers, among other
wasasignificantcontributortoHgaccumulationinTaiwanese. things. In addition, Hg contamination is more widespread because
aircontaminatedwithHgvaporistransportedacrossnationalbound-
3.4.Areapollution ariestoneighboringcountriesandbeyond.Hgintakethroughfood,
particularlyriceandfish,wasthemostimportantrouteofHgexpo-
Our findings suggest that the remarkably high blood T-Hg and sure,however,themostriskislocatedinthevicinityofsmeltingfacil-
MeHglevelsinTaiwanmightbeattributabletothenumberofweekly ities,miningactivitiesandclosetothewastedisposalsitesforgeneral
fishmealseatenbyTaiwaneseorhighMeHgcontaminationinfishof population(Horvatetal.,2003).Astudy(PalhetaandTaylor,1995)
Taiwan,especiallyineasternandsouthernTaiwan,whereresidents that compared T-Hg and inorganic Hg levels between unpolluted
had significantly higher T-Hg levels than in central and northern areasandHg-pollutedgoldminingareasintheAmazonregionofBrazil
Taiwan. Hsu et al. (2006) reported very high Hg levels found in showedthattheenvironmentalHgwastransferredtofishandanimals
usedforfoodand,subsequently,intothepeoplewhoconsumedthem.
Table5
Intakefrequencyofseafoodbetweentheinhabitantlivingnearcoastalandinlandsites 4.Conclusions
(time/month).
SignificantlyhigherT-HgandMeHglevelswerefoundinresidentsof
Types Coastalsites Inlandsites P-value
(N=262) (N=303) Taiwan's coastal sites than inland sites. The elevatedT-Hg andMeHg
levels appeared to be related to eating large-sized remote sea fish,
Large-sizedremoteseafish 3.77±8.4 3.09±6.5 0.950
Small-sizedremoteseafish 3.42±6.4 3.26±6.6 0.771 small-sized remote sea fish, shrimp, crab, and octopus. Of the four
Small-sizedoffshoreseafish 5.06±11.8 2.62±5.4 b0.001⁎ areas that we investigated, the highest T-Hg and MeHg levels were
Cultivatedfish 1.67±2.9 1.66±2.8 0.935 foundintheleastindustrializedarea,Yilan,ineasternTaiwan,andthe
Freshwaterfish 3.06±5.6 3.58±6.1 0.014⁎⁎ next highest were in the highly industrialized area of Kaohsiung, in
Shrimp 2.71±5.2 2.52±6.7 0.015
Shellfish 3.25±4.0 3.65±7.7 b0.001⁎ southernTaiwan.Toprotectourcitizensfromaccumulatingtoomuch
Oyster 2.76±6.9 1.62±5.4 b0.001⁎ HgandMeHgintheirbloodbecauseofthefoodtheyeat,itisnecessary
Octopus 3.06±6.3 2.11±5.5 0.023⁎ toexaminetheprimarylocalsourcesofseafoodinparticular,especially
forsensitivepopulationslikechildrenandpregnantwomen.Webelieve
Note:thedatameantmean±standardizedeviation,TestbyWilcoxonRankSumsTest.
⁎ P-valueb0.05. thatinvestigationsofthelocalsourcesofHgpollutionarejustified.
C.-C.Leeetal./ScienceoftheTotalEnvironment424(2012)316–321 321
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