Studies made to assess risk concerning a 'dioxin' contamination incident near Bolsover, Derbyshire, UK

During 1990 and 1991, milk samples were collected from farms in Derbyshire, a county in the UK, as part of a study designed to establish background concentrations of polychlorinated dibenzo- p -dioxins and furans (PCDD/Fs) in cows' milk produced in the area. The concentrations found in two samples, both taken from farms near the town of Bolsover, were significantly elevated (40.0-42.0ng TEQ kg -1 fat) when compared with the normal range for these compounds in milk from the surrounding area (1.1-7.1 ng TEQ kg -1 fat). An immediate intensive programme commenced in April 1991 to test milk from a further 27 dairy farms close to those where the original 'high' samples were obtained. A maximum tolerable concentration (MTC) was calculated to be 17.5 ng/TEQ kg -1 fat. This was derived by using the tolerable daily intake (TDI) for 2,3,7,8-TCDD of 0.01 ng kg -1 body weight day -1 set by the World Health Organization in 1990 and accepted by the UK government (this figure has since been revised to 1-4 pg kg -1 body weight day -1 ). MTC is defined as the amount of PCDD/Fs that could be present and still ensure that high-level (97.5 pecentile) consumers of milk would not exceed the TDI. Milk originating from dairies supplied by these farms and others contained PCDD/F in the range 1.8-3.1 ng TEQ kg -1 fat, which indicated there was no risk to health for consumers purchasing milk in the normal manner. Milk from the two dairy farms was removed from the food supply until concentrations of PCDD/Fs were consistently below the MTC. The UK Department of Health monitored the blood concentrations of PCDD/Fs in individuals who had consumed milk produced on the affected farms and the Department of the Environment initiated a programme of work to identify and reduce the source of pollution.