Research exploring the possible health risks of chemicals may be flawed because the mice used in lab experiments may be genetically tolerant of the pollutants to which they are being exposed, according to a new study in the journal Science. Researchers at the University of California at Davis exposed several strains of mice to chemicals that mimic the female sex hormone estrogen and are found in some pesticides, plastics, and household detergents. Although all strains of mice studied showed some signs of estrogen disruption, one strain, which is often used in lab tests, suffered far less than the others. Meanwhile, a panel of experts announced yesterday that phthalates, chemical additives found in consumer products ranging from baby bottles to intravenous drip bags, disrupt reproductive functions in lab animals and may be dangerous to humans. Still, the panel said it needs more time to reach final conclusions about impacts on humans.

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