A global study of toxic substances entering the human food chain gets under way this month.The United Nations Environment Programme's US$5m, two-year project aims to identify persistent organic pollutants (POPs) found in pesticides and industrial waste, which can be present in food at dangerous levels.It goes further than the 12 substances described by UNEP as "posing aserious threat to humans and the environment," which are the subject of an international treaty aimed at reducing their use. These include DDT, dioxins and flurans.Klaus Toepfer, UNEP executive director, said: "There is clearly a need for a scientifically based assessment of the nature and scale of the threats to the environment and public health from persistent toxic substances that goes beyond the list of 12 persistent organic pollutants."Conclusions from the full-scale project will assist in establishing future priorities, help countries and regions in developing responses to risks from these pollutants, and, in the longer term, contribute to identifying additional POPs for international action."UNEP has also released a report which shows that of more than 100 developing countries, two thirds are on target to reduce emissions of ozone depleting substances, under their commitments to the Montreal Protocol.