(JP)Environmental hormones strike offshore

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http://www.asahi.com/english/feature/K2001070902772.html

 

Environmental hormones strike offshore

 

The Asahi Shimbun

 

The ocean is not big enough to prevent estrogen-like

pollutants from having an increasing effect on coastal

fish, giving them an abnormal level of female

attributes, researchers say.

 

The prevalence of the feminized fish is greater in

waters near urban areas that produce large amounts of

industrial and household waste water, the researchers

found.

 

With few precedents to go on from elsewhere in the

world, the National Institute for Environmental

Studies, meanwhile, is planning a national survey of

the effects of environmental estrogen on fish.

 

A research group led by Shinya Hashimoto, an associate

professor at the University of Shizuoka, gathered male

gizzard shad from coastal waters in the Kanto region

last year. Hashimoto's group looked at the gonads of

73 male fish, of which three had cells of the type

that form eggs and are normally found in female fish.

One of the fish had 12 such cells in its gonads.

 

In another study, a group headed by Takahiro Matsubara

of the Hokkaido National Fisheries Research Institute

collected male goby at 19 locations, from the Kanto

and Chubu regions to Kinki and Kyushu. The specimens

they collected offshore from the Chubu region had up

to 25 times more vitellogenin, a protein normally

found in female fish, than did goby caught in

relatively clean waters off Hokkaido. Those caught in

waters off the Kinki region had vitellogenin levels 60

times higher than the Hokkaido fish.

 

Kiyoshi Soyano, an associate professor of the Faculty

of Fisheries at Nagasaki University, was involved in a

joint research project from 1999 to 2000 that studied

blood samples from 91 male striped mullet collected

offshore of the Kinki and Kyushu regions. The average

vitellogenin level in fish caught near urban areas of

Kyushu was 10 times higher than that of fish caught in

clean waters. In fish caught near the metropolitan

areas of the Kinki region, it was about 1,000 times

higher.

 

Soyano said the amount of the protein found in the

Kinki-region fish was ``at extremely abnormal levels

that would only appear if female hormones were

injected directly into the fish's body.''

 

In those fish, the group found an average of 1,755

micrograms of vitellogenin per milliliter of plasma.

 

Three years ago, Hashimoto and some of his colleagues

reported at an academic conference that they had found

high levels of vitellogenin in blood samples from male

flounder caught in waters near the Kanto region. A

British study of flounder produced similar results.

 

But most scientists at the time believed the effect of

pollutants on saltwater was minimized by the sheer

size of the ocean. The findings of the flounder

research was thought to be unrepresentative because

that species was particularly sensitive to chemical

contamination.

 

But now that traces of environmental estrogens are

turning up in other fish, Hashimoto said, it can no

longer be argued that the flounder is a special case.

 

He nevertheless expressed surprise at the findings for

saltwater fish, saying scientists had previously

believed the oceans were less susceptible to pollution

than were rivers.

 

Past studies in both Japan and abroad have shown

environmental estrogens in freshwater fish such as

carp and rainbow trout.

 

Experts said that if abnormal feminization were to

spread to other types of fish, it could affect their

fertility rates and cause a decline in the commercial

fish harvest.

 

As for the human consumption of fish contaminated with

environmental estrogens, Masatoshi Morita of the

National Institute for Environmental Studies said

people eating such fish would suffer no immediate ill

effects. He added, however, that more studies would be

required before he could say such fish are completely

safe to eat.

 

Other researchers said the latest findings could be

seen as a warning to humans.

 

``The fishes are of a type that normally would have

clear distinctions between male and female,'' said

Kiyoshi Fujita of the Tokyo University of Fisheries.

``The phenomenon of more feminine male fish is some

sort of warning.''

 

Scientists have several suspicions as to the cause of

the problem. Hideshige Takada, an associate professor

at the Tokyo University of Agriculture and Technology,

said possible candidates include the female hormone

17-beta-estradiol, which is found in human and animal

waste, as well as nonylphenol, an industrial

detergent. But he added that some as-yet undiscovered

chemical may also be responsible.

 

The Ministry of Land, Infrastructure and

Transportation found in a May study on environmental

estrogens in the sewage system that while 97 percent

of the nonylphenol was removed in sewage processing,

only about 80 percent of 17-beta-estradiol was

removed. In some facilities, only about 15 percent of

the 17-beta-estradiol was removed before the water was

released.

 

(07/10)

 

 

 

 

 

 

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