Until recently, endosulfan was one of the most widely used pesticides. Some others -- toxaphene, dieldrin, and chlordane -- were banned or restricted in many countries in the 1980s but linger in the environment. All four have a weak effect individually in increasing estrogen levels in women. Scientists have found, however, that their potential to cause health hazards increases dramatically when the chemicals are combined. For example, a mixture of endosulfan and dieldrin had 160 to 1, 600 times more estrogen-boosting potency than either chemical did individually. Increased estrogen is associated with an increased cancer risk in women.
If certain pesticides combine in the environment, they may constitute greatly increased human health hazards is most strongly supported by the information above.