Persistent organic pollutant

A persistent organic pollutant (POP) is an organic compound that is only slowly degraded in the environment, so that it tends to persist and even to accumulate rather than being broken down by photochemical or biological processes. Accumulation can occur either in the environment (eg, in sediments) or in the tissue of animal or plant species (bioaccumulation).

Public concern about persistent organic pollutants was first raised in the early 1960s with the publication of the book Silent Spring (1962) by U.S. author Rachel Carson (1907–64), which led to the banning of DDT for agricultural use in the United States in 1972. The U.S. and several other countries have regulated POPs on a case-by-case basis since then. A more systematic approach to the regulation of POP production and use can be found in the Stockholm Convention on Persistent Organic Pollutants, signed in 2001, and the European Union REACH Regulation (1907/2006).

Definitions

A persistent organic pollutant could simply be defined in terms of its persistence in the environment, which would include substances such as crude oil. However, it is more normal also to take account of the potential for bioaccumulation and any toxicity associated with the substance. Candidates for regulation under the Stockholm Convention or the REACH Regulation are usually either PBT substances (persistent, bioaccumulative, toxic) or vPvB substances (very persistent, very bioaccumulative).

	Stockholm Convention	REACH Regulation
Persistence	half-life in water > 2 months; or half-life in soil > 6 months; or half-life in sediment > 6 months.	P	half-life in marine water > 60 days; or half-life in river or esturine water > 40 days; or half-life in marine sediment > 180 days; or half-life in river or esturine sediment > 120 days; or half-life in soil > 120 days.
		vP	half-life in water > 60 days; or half-life in sediment > 180 days; or half-life in soil > 180 days.
Bioaccumulation	bioconcentration factor for aquatic species > 5000. In the absence of other data, log Kow > 5.	B	bioconcentration factor for aquatic species > 2000.
		vB	bioconcentration factor for aquatic species > 5000.
Toxicity	generic criteria only	no observed effect concentration (NOEC) for aquatic species < 0.01 mg/l; or substance is classified as carcinogenic (1A or 1B), germ cell mutagenic (1A or 1B) or toxic for reproduction (1A, 1B or 2) under the CLP Regulation; or substance is classified as STOT (repeated exposure) 1 or 2 (oral, dermal, inhalation of gases/vapours, inhalation of dust/mist/fume) under the CLP Regulation.