asked Her Majesty's Government:

How many parts per million of Aroclor 1254 in water would affect the immune, neurological, reproductive and endocrine systems of fish, rats, sheep, cattle and humans; what levels would cause death; for how long the chemical remains active in the environment; and for how long these effects have been known. [HL3346]

Aroclor 1254 is a mixture of more than 80 different polychlorinated biphenyl (PCB) chemicals. PCBs are practically insoluble in water. Available data for aquatic life indicate effects on mortality, growth and reproduction at concentrations of 8 micrograms/litre. There is little information on the effects on sheep or cattle, nor on the endocrine-disrupting effects of PCBs on aquatic life. A single oral dose of 1 to 1.3 grams of Aroclor 1254 per kilogram of bodyweight has been reported as sufficient to kill half a group of treated rats.

The UK Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment (COT) issued a statement on PCBs in 1997, and recommended that, where humans are exposed to a mixture of PCBs, the risk to health can be assessed by reference to the tolerable daily intake (TDI) rather than concentration. The TDI is based on the most sensitive end-point and will protect against the risk of other adverse effects.

After reviewing the animal toxicity data on commercial PCB mixtures, COT concluded that the most critical effects—that is, those seen at the lowest level of exposure—are those on the skin, the immune system, reproduction and postnatal behavioural development. It was not possible to derive no adverse effect levels (NOAELs) for these effects from the available data but it is possible to derive lowest observed adverse effect levels (LOAELs) by means of tests on animals. A LOAEL of 5 micrograms (micrograms)/kg bw/day for Aroclor 1254 was identified for effects on the skin and on the immune system, while the effect on the reproductive system was considered to lie in the range from 5 to 30 micrograms/kg bw/day.

In the UK, the sale of PCBs for use in open applications was prohibited in 1972 and their manufacture and use in new plant and equipment prohibited in 1986. Since then, the phase-out of any remaining uses has been of PCBs sealed in older equipment and phase-out by 2010 is required by EU legislation. Action has been taken at both national and global level; the UK is a signatory to the Stockholm convention, a global treaty signed by 151 countries with the objective to protect human health and the environment from a range of 12 chemicals known as persistent organic pollutants including PCBs. Under the convention the use, manufacture, import and export of the 12 listed substances including PCBs is banned.