Harmless chemicals are poisonous in combination
According to New Scientist, (01/09/2007, p.46), Earl Gray, an ecotoxicologist at the reproductive toxicology division of the US Environmental Protection Agency’s Health and Environmental Effects Research Laboratory (HEERL) in Research Triangle, North Carolina, and his team while exposing pregnant rats to vinclozolin and procymidone – in order to study the impact of the chemicals to the reproductive capacity – saw no effect when they exposed the animals to the compounds individually, however, when they combined the two, half of the males were born with hypospadia – a phenomenon called by Gray as "the new math – zero plus zero equals something".