Women with breast cancer five times as likely to have pesticide (DDT) residues in their blood

Women with breast cancer are five times as likely to have pesticide residues in their blood of organochlorines (DDT), which contain oestrogens, reveals a study of 159 women in Occupational and Environmental Medicine.

The possibility of such a link has attracted controversy, admit the authors, but say that their new study adds to the growing body of evidence for an association between environmental oestrogens and the rising incidence of breast cancer.

The authors base their findings on a study of 600 women referred for breast lumps between September 1999 and February 2000 to one hospital in Liége, Belgium.

Of the total, 159 women were diagnosed with breast cancer and subsequently admitted for the removal of the tumour or the whole breast. The women’s average age was 54.

Before surgery or drug treatment, the women were tested for total levels of organocholorines (DDT) and hexachlorobenzene (HCB) in their blood.

This was done to ensure that the results would not be affected by weight changes brought about by chemotherapy and radiotherapy, so altering levels of fatty tissue where organochlorines accumulate.

DDT was effectively banned for use as a pesticide in the US in 1972, almost 30 years after it was introduced for this purpose. But DDT can remain active in tissues for up to 50 years.

The blood samples were compared with those taken from 250 healthy women, matched as closely as possible for age, menopausal status, reproductive history, and smoking habit.

The results showed significant differences between the two groups of women. Those with breast cancer were over five times as likely to have detectable levels of DDT above 0.5 parts per billion as the healthy women, and more than nine times as likely to have detectable levels of HCB in their blood. The highest levels detected were 20 parts per billion.

Some women’s breast tumours are sensitised to, and sustained by, oestrogen. But DDT or HCB levels were no higher for the 102 women in this study to whom this applied.

The authors are quick to point out that while their research does not prove a definitive link between oestrogenic pesticide residues and breast cancer, there is plenty of published evidence on the ability of hormones to promote animal and human cancers. And research has shown that DDT, and its major metabolite DDE, have oestrogenic properties.