THE adverse effects of gender-bending chemicals released into the environment have been grossly underestimated. A researcher says tests to evaluate the dangers are flawed because they don鈥檛 take into account the cumulative effect of mixing the chemicals.
Synthetic substances that mimic oestrogens have been linked to sex changes in animals (see above) and increased levels of breast and testicular cancer in people. That has prompted the industries that use or make the substances to carry out animal tests to confirm what levels could cause ill effects.
鈥淏ut industry only tests single substances and doesn鈥檛 look at the low-level mixtures of them found in the real world,鈥� says Andreas Kortenkamp at the School of Pharmacy, University of London.
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Kortenkamp made up a mixture of eight oestrogenic compounds such as bisphenol A and hydroxylated PCBs that are found in water, canned food or sunscreens. Crucially, each compound was present at just half the concentration deemed to have no observable effect on oestrogen receptors in cells.
To test the effect of the mixture, Kortenkamp genetically engineered yeast cells to make the human oestrogen receptor. When oestrogen or chemicals that mimic it bind to the receptor, the yeast produces an enzyme that turns the gel supporting the yeast cells from yellow to red.
His results were striking. 鈥淲e had a mixture of chemicals, each present at levels so low you鈥檇 see no effect from them individually. But combined, you get a strong effect,鈥� says Kortenkamp. He says scientists will have to allow for the effect of mixing chemicals, even if they鈥檙e at extremely low concentrations.