Environmental Engineering Reference
In-Depth Information
The. Pearl. River. Delta. has. undergone. a. rapid. socioeconomic. develop-
ment.over.the.past.30.years.since.the.economic.reform,.with.environmental.
degradation.resulting.as.a.consequence.(Enright.et.al..2005)..During.the.pro-
gression.of.different.stages.of.industrial.development,.different.toxic.chemi-
cals. have. been. emitted. through. human.activities.. These.could.be. grouped.
under. (1). heavy. metals,. (2). Stockholm. Convention-classiied. persistent.
organic.pollutants.(POPs),.and.(3).chemicals.of.emerging.concern.
Heavy Metals
It. is. commonly. known. that. arsenic. (As,. a. metalloid),. cadmium. (Cd),. mer-
cury.(Hg),.and.lead.(Pb).are.widespread.in.the.environment..A.substantial.
amount. of. information. concerning. the. sources,. fates,. and. effects. in. Hong.
Kong.and.the.Pearl.River.Delta.region.has.been.available.since.the.1970s.
Based.on.the.bioaccessible.heavy.metal.results.from.our.recent.investigation.
(Man.et.al..2010),.it.was.revealed.that.the.concentrations.of.As.and.other.heavy.
metals.found.in.the.soil.of.former.agricultural.lands.are.highly.detrimental.
to.the.human.health.(especially.to.children).due.to.electronic.waste.storing.
and. recycling,. car. dismantling. and. repairing. activities. that. causes. drastic.
increases.in.concentrations..In.addition,.high.concentrations.of.As,.Cd,.Hg,.
and.Pb.in.water.and.sediment.giving.rise.to.elevated.levels.of.their.presence.
in.ish.would.also.impose.potential.health.risk.
According. to. a. study. on. the. levels. of. Hg. in. six. ish. species. cultured. in.
the. same. pond,. there. is. a. clear. indication. that. Hg. is. bioaccumulated. and.
biomagniied. in. the. aquatic. food. chain,. with. the. highest. concentration.
(56.7.ng/g. dry. wt.). detected. in. the. black. bass,. a. top. carnivore. (Zhou. and.
Wong.2000;.Cheng.et.al..2010).
An.early.study.indicated.that.individuals.consuming.four.or.more.meals.of.
ish.per.week.had.a.hair.Hg.of.4.07.mg/kg.dry.weight.while.those.consuming.
ish. less. frequently. had. signiicantly. lower. levels. (2.56.mg/kg),. and. men.
with.high.hair.levels.were. twice.as.likely. to.be.subfertile,. when.compared.
with.men.with.low.levels.(Dickman.et.al..1998,.Dickman.and.Leung.1998)..
Secondary.school.students.in.Hong.Kong.have.been.advised.not.to.consume.
excessive.amount.of.predatory.ish.(such.as.tuna),.which.may.contain.higher.
Hg,. as. well. as. shellish,. which. contains. higher. As. and. Cd. concentrations.
(HKFEHD.2002).
In. fact,. our. previous. study. testing. heavy. metals. in. common. freshwater.
and. marine. ish. available. in. Hong. Kong. markets. indicated. that. a. few. ish.
species.had.average.concentrations.greater.than.the.international.standards.
for.Cd.and.Pb.established.by.the.European.Union.and.the.China.National.
Standard. Management. Department.. Total. Hg. concentrations. in. 10. of. 20.
ish.species.available.in.the.market.were.generally.greater.than.those.of.the.
World. Health. Organization's. recommended. limit. of. 0.2.mg/kg. for. at-risk.
groups,.such.as.children.and.pregnant.women.(Cheung.et.al..2007).
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