Researchers know that chemicals which behave like oestrogen can cause health problems.
They can have a dramatic effect on animals, for example turning fish into hermaphrodites. Some researchers claim that hormonally active chemicals from the urine of women taking the birth control pill are already swamping the environment, and may be causing a decline in sperm counts. Uterine growth Schlumpf and her colleagues tested six common UV screening chemicals used in sunscreens, lipsticks and other cosmetics. Three caused developmental effects in animals. One of the most common sunscreen chemicals, 4-MBC, had a particularly strong effect.