test mice insensitive to estrogens; phthaltes review

[ttweed@wildrockies.org (Tony Tweedale)]

Friday, August 20, 1999 Published at 09:01 GMT 10:01 UK

Sci/Tech [BBC]

Worry on 'gender bender' tests

Endocrine disrupters are a concern to all industrialised societies

There is a flaw in the way scientists test for the some of the
damaging effects of chemicals in the environment.

Research has shown that the mice used in some lab experiments,
because of their genetic make-up, may actually be quite tolerant of
the pollutants to which they are exposed. As a result, it is possible
that the testing is underestimating the dangers that come from
these pollutants.

Of particular concern are the chemicals that mimic the female sex
hormone oestrogen. They are sometimes referred to as endocrine
disrupters or "gender benders" because of the way they appear to
interfere with reproduction in fish and other wildlife by upsetting
the normal function of the endocrine system.

The evidence is not wholly conclusive, but studies indicate that
such chemicals can cause decreased sperm counts, deformed
genitals, aberrant mating behaviour and sterility.

Lab tests

"Environmental oestrogens" have been found in products such as
DDT and other pesticides, some plastics, industrial chemicals like
PCBs, and even household detergents.

Government agencies and research labs test the chemicals on lab
mice, but new research, published in the journal Science shows the
wrong type of rodents may be being used.

A team from the University of California, Davis, analysed the
effects of oestrogen doses given to several strains of laboratory
mice developed under different selective breeding conditions.

Although all the strains of mice exposed to the oestrogen showed
some signs of endocrine disruption - including smaller testes
weight and inhibited sperm production - one strain of mice
suffered far less than the others.

Testes function

This particular strain, known as CD-1, was 16 times more
resistant to the damaging effects of the oestrogen on testes function.

CD-1 mice are frequently used in toxicological and pharmacology
studies, and are specially selected to produce large and vigorous
litters for the purpose. The researchers suggest that the genes
controlling large litter size in these mice might also be affecting
their sensitivity to oestrogen, making them a poor model for
studying endocrine disruption.

"The use of laboratory animals that genetically are quite resistant
to oestrogen for the evaluation of possible reproductive effects of
various chemicals might be misleading and may mask our
appreciation of how global exposure to oestrogen-like chemicals
threatens wildlife, domestic animals and humans," said Jimmy
Spearow, a reproductive geneticist, who worked on the UCDavis
research.

"Considering these genetic variations in the oestrogen sensitivity of
an individual or species will be important not only when testing for
endocrine-disrupting properties in industrial chemicals and
pesticides, but also when determining therapeutic doses of
oestrogen and related steroid compounds in human medicine."

----



Experts think plastics may be dangerous, but more study needed

Copyright © 1999 Nando Media
Copyright © 1999 Reuters News Service

>From Time to Time: Nando's in-depth look at the 20th century

By MAGGIE FOX

ALEXANDRIA, Va. (August 19, 1999 8:02 p.m. EDT http://www.nandotimes.com) -
Chemical additives found in a range of consumer products from baby bottles
to intravenous drip bags may be dangerous to humans, a panel of experts
said on Thursday, but they said they needed more time to decide.

Members of a panel asked to determine the health risks from the chemicals,
known as phthalates, had been expected to issue a final report on their
findings on Thursday, but ran out of time before reaching a consensus.

While they said there was little disagreement over what the studies show --
that the chemicals can disrupt reproductive functions such as fertility in
laboratory animals -- what was not clear was whether they affect humans.

"Some of the phthalates we looked at, like DEHP and BBP, are reproductively
toxic in rats and mice," Robert Kavlock of the Environmental Protection
Agency, who chaired the panel, told reporters.

"When exposure happens earlier in life, the effects tend to be more severe."

Dr. Lynn Goldman, a pediatrician at Johns Hopkins University in Baltimore
and senior scientific adviser to the National Toxicology Program, agreed.
"You can see both developmental impacts ... like birth defects, and
reproductive effects on sperm and fertility," she said.

But she added, "Even though there is a lot of production of these chemicals
and even though there is a lot in the environment, we know very little
about what human exposure is."

Goldman said the chemicals, used to soften plastics, can leach out. "Some
are used in fairly sensitive areas such as blood tubing and IV bags where,
if they are coming off, they have the potential to go directly into a
person."

In June a coalition of 181 health, religious, labor and environmental
groups, called Health Care Without Harm, petitioned the Food and Drug
Administration to warn patients about phthalates in IV bags.

The environmental group Greenpeace said phthalates could leach from soft
vinyl toys into the mouths of children when chewed or sucked, and in
December the Consumer Product Safety Commission asked the nation's
toymakers to remove phthalates from baby rattles and teething toys.

But the chemical industry and groups such as the Health Industry
Manufacturers Association say products using phthalates are safe. An
earlier panel chaired by former Surgeon General Dr. C. Everett Koop agreed.


The new panel -- the first of its kind to examine a chemical in such a way
-- was asked to determine whether the population is at risk from the
chemicals.

Goldman would not say which way they group was leaning.

The panel, appointed by the Center for the Evaluation of Risks to Human
Reproduction, itself a branch of the NTP and the National Institute of
Environmental Health Sciences, will try to meet again later this year.

"The decision was to have more discussions, so that we feel comfortable
(with any statement)," Goldman said.

The committee, appointed earlier this year, includes experts in toxicology,
pediatricians and others. They heard evidence from the chemicals and
plastics industries, medical experts and advocacy groups, and read more
than 1,000 scientific papers looking at the effects of phthalates.