Chlorpyrifos as a possible global POP

Chlorpyrifos is an organophosphate pesticide with a wide variety of crop and non-crop uses. Modelling studies indicate that chlorpyrifos meets Stockholm Convention criteria for persistence under Arctic conditions and it has been found in Arctic ice dating back to 1971. Chlorpyrifos persists in termiticide treatments using high application rates and in freshwater sediment under anaerobic
conditions.

Chlorpyrifos exceeds Stockholm Convention criteria for bioaccumulation with most reported values of log Kow meeting or exceeding 5.0. Chlorpyrifos undergoes long-range transport and has been measured consistently in the Arctic, in ice, snow, fog, air, seawater, lake sediment, fish and vegetation. It is amongst the pollutants with the highest concentrations present in the Arctic, in excess of most legacy POPs pesticides. Chlorpyrifos is highly toxic to aquatic organisms and a potent developmental neurotoxin at low levels of exposure, below those that trigger foetal cholinesterase inhibition.

Chlorpyrifos is an endocrine disrupter with anti-androgenic and oestrogenic properties and reduces serum levels of cortisol and thyroid hormone T4. Exposures in utero and in early childhood can lead to behavioural anomalies in adolescence and adulthood. Epidemiological studies in humans found delayed cognitive and psychomotor development, and reduced IQ. Chlorpyrifos has been detected in human breast milk, cervical fluid, sperm fluid, cord blood, and the meconium of newborn infants.

Chlorpyrifos is released directly to the environment when it is applied as a pesticide. Use of the substance has greatly increased since its introduction in 1965. Alternative techniques for avoiding the use of chlorpyrifos are available for all or most of its uses. These include cultural and mechanical techniques, biological controls and other chemicals. Since chlorpyrifos can move far from its sources, individual countries or regions cannot protect themselves or abate the pollution caused by it. Due to its harmful POP properties and risks related to its widespread production and use, international action is warranted to control chlorpyrifos.

Source: Meriel Watts, For Pesticide Action Network North America
August 2012