Pollution is generallyy defined as the release of harmful environmental contaminants. Pollution can take two major forms: local pollution and global pollution. In the past, only local pollution was thought to be a problem. For example, coal burning produces smoke and in sufficient concentrations can be a health hazard. One slogan, taught in schools was "The solution to pollution is dilution". In recent decades, awareness has been rising that some forms of pollution pose a global problem.

Traditionally, serious pollution sources include chemical plants, oil refineries, nuclear waste dumps, regular garbage dumps (many toxic substances are illegally dumped there), incinerators, PVC factories, car factories, plastics factories and corporate animal farms creating huge amounts of animal waste.

Lead is still the single most important chemical toxin for children and is probably the best known example of a neurotoxin to which children are particularly vulnerable. Their special vulnerability to lead is related to their exposure (hand