Category: More Bad News About Frogs. Those amphibian-lovers who were dismayed to learn last week that frogs and their fellow kind are being rendered hermaphroditic and otherwise sexually odd by exposure to herbicides will be even more disheartened by the news that trace amounts of DDT and other pesticides administered in lab tests caused near-total collapse of froggy immune systems. The finding could explain declining levels of amphibians worldwide, as well as rising levels of human autoimmune disorders such as asthma and allergies, according to the Canadian researchers who conducted the study. Two of the pesticides used (DDT and dieldrin) are on the U.N.’s list of the world’s most toxic substances, but despite being banned in many countries, they resist decay and persist in the environment. The third insecticide, malathion, is still widely used on crops and for mosquito control.