Beef from farms in two Australian states has been rejected for export, after it was found to be contaminated with excessive insecticide residues.

The chemical concerned, endosulfan, is an organochlorine insecticide. Many governments have severely restricted or even banned it, because it is highly poisonous to humans.

Endosulfan is also one of the endocrine disrupters, chemicals which interfere with naturally produced hormones.

It is believed to mimic the effect of the female hormone oestrogen - chemicals capable of doing this have been linked to carcinogenic effects.

Endosulfan remains approved for use in Britain.

The United Kingdom imported 9,500 tonnes of Australian beef in 1997.

The Ministry of Agriculture says customs officers are responsible for checking imports - they are able to check samples, not every import.

A Ministry spokesman told BBC News Online: "If they knew what they were looking for, they would have the expertise and equipment to find it.

"But they would not necessarily find things they did not know to look out for."

Substantial breach in levels

The maximum endosulfan residue level allowed in beef sold in Australia is 0.2 mg/kg, twice the level permitted internationally.

Pesticide Action Network North America, reporting the discovery, says the tainted beef has been found in carcasses from farms in New South Wales and Queensland, where some recent samples showed levels of 0.36 mg/kg.

Idyllic - but Queensland has problems

A spokesman for the Australian Agriculture Ministry said the excess residues were probably caused by increased planting of cotton, and the resultant high use of pesticides to control insects.

Cotton planting is expected to rise by about 25% this year, to roughly 547,000 hectares.

The cattle absorb the poison when pesticides drift from cotton fields onto their pasture, or when they are fed cotton waste containing the chemical.

The Australian National Residue Survey has identified about 1,400 cattle farms as vulnerable to contamination form cotton growing.

Call for reduction

Cattle from these farms are closely monitored for any sign of excessive endosulfan residues.

The country's National Registration Authority (NRA), the government body which regulates pesticide use, has urged cuts in the use of endosulfan.

It has also imposed some restrictions to try to limit the impact on workers and on the environment.

But a proposal to limit applications of the chemical to a range of "essential" uses was abandoned in the face of lobbying by the cotton industry.

Cattle are at risk from cotton spraying

In 1996 more than 20 farms in New South Wales and Queensland were quarantined after inspectors found endosulfan residues in cattle above the maximum permitted level.

Lawyers for the farmers said that NRA restrictions on endosulfan use were inadequate.

That year newborn calves in Australia were found to be contaminated with hazardous levels of another insecticide, chlorfluazuron.