The dioxin affair began last year when analyses by MAFF revealed that milk from two farms close to Coalite's plant was contaminated with dioxins. Subsequent tests by HM Inspectorate of Pollution (HMIP) pinpointed an incinerator on the site as the source. NRA investigations showed that the scrubber liquor from the incinerator was contaminating the river Doe Lea with dioxins (ENDS Reports 202, pp 16-20, and 203, pp 4-5).
Formal samples of the river sediments taken by the NRA in April revealed that total dioxin and furan concentrations immediately downstream of Coalite's plant reached up to 5,900ng/kg, expressed as the toxic equivalent (TEQ) of the most toxic of the dioxins, 2,3,7,8-TCDD. Upstream the levels were all less than 5ng/kg. Dioxin traces were still being discharged by the works, although the incinerator was shut down for improvements in November on HMIP's orders.
Coalite's discharge consent does not mention dioxins. And it covers only the effluent from coke and chemical production, and does not explicitly sanction the discharge of incinerator scrubber liquor.
The NRA's investigations suggest that dioxins are moving down the Doe Lea. Although dioxin levels in the sediments close to the works have fallen since last November by a factor of ten, the decline has been less marked further downstream. Last autumn, sediments 1.2-1.5 kilometres downstream contained 32,000-54,000ng/kg TEQ. The latest NRA samples show levels of about 18,000ng/kg.
The contamination is apparent 20 miles downstream where the river Rother meets the river Don at Rotherham. Dioxin levels in the Don's sediments are around 65-70ng/kg TEQ, which the NRA attributes to the contamination of the Doe Lea.
The NRA says that dioxins are likely to be deposited on farm land as both the Rother and Don are prone to flooding. Dredgings from the Don are also tipped on the banks.
Meanwhile, a further MAFF report has concluded that the pattern of dioxins in herbage on three farms close to Coalite's plant suggests that much of the contamination has been caused by recent deposition from the air.1Analyses of tissues from several cattle raised on one of the contaminated farms which were kept on dioxin-free diets for some weeks before slaughter indicate that milk secretion is an important pathway for dioxin excretion. MAFF believes that animals with a heavy body burden of dioxins which are not lactating will retain a high level of contamination for "a very protracted period". An order banning the sale of animals and animal products from the farm was renewed in June.
During a debate on the order in the House of Lords on 23 June, junior Agriculture Minister Earl Howe revealed that dioxin levels in the blood of the family living on the farm have been found to be "somewhat elevated", but the Department of Health had advised that they are "highly unlikely to suffer adverse health affects as a result." The results are confidential. The Department of Health failed to respond to questions about what it regards as an acceptable blood dioxin level.