Environmental chemicals and cancer: study suggests closer link

Paul Boughton

Previous studies in cancer causation have often concluded that exposure to carcinogenic or endocrine-disrupting chemicalsfor exampleorganochlorines (OC) – found in pesticides and plastics – occurs at concentrations that are too low to be considered a major factor in cancerous disease.

Now new research at the University of Liverpoolpublished in the Journal of Nutritional and Environmental Medicinehas found that exposure even to small amounts of these chemicals may result in an increased risk of developing cancer – particularly for infants and young adults.

The research consisted of systematic reviewing of recent studies and literature concerning the environment and cancerand was supported by the Cancer Prevention and Education Society. Professor Vyvyan Howard and John Newbyfrom the University's Department of Human Anatomy and Cell Biologyalso found that genetic variationswhich can predispose some people to cancermay interact with environmental contaminants and produce an enhanced effect.

Howard said: “Organochlorines are persistent organic pollutants (POPs)which
disperse over long distances and bioaccumulate in the food chain. For humans the main source of OC exposure is from dietprimarily through meat and dairy products.

“Children are exposed to dioxina by-product of OCsthrough food; dioxin and other POPs can also cross the placenta and endanger babies in the womb. Breastfed infants can be exposed to OCs with endocrine disrupting properties that have accumulated in breast milk. Our research looks at involuntary exposure to these chemicals in the airfood and water.”

The research team has also looked at anecdotal evidencefrom practicing physicians in pre-industrial societieswhich suggests that cancerous disease was rare among particular communitiessuch as the Canadian Inuits and Brazilian Indians. This suggests that cancer is a disease of industrialisation.

Howard concluded: “The World Health Organisation estimates that between one and five per cent of malignant disease in developed countries is attributed to environmental factors; but our research suggests this figure may have been underestimated.”

The researchers also point out: the incidence of cancer in the UK has risen between 1971 and 1999; non-Hodgkin’s lymphoma has risen by 196 per cent in men and 214 per cent in women; prostate cancer and testicular cancer have risen by increased by 152 per cent and 139 per cent respectively; breast cancer has risen by 75 per cent and multiple myeloma by 100 per cent and 86 per cent in men and women respectively.

Jamie Pagechairman of Cancer Prevention and Education said: “This research is very important and suggests that there are links between chemicals and cancer. It is our opinion that if progress if to be made in the fight against cancerfar more attention and effort must be made to reduce human exposure to harmful chemicals.”

PCB and dioxin levels for food

As the Liverpool scientists were publishing their findingsthe European Commission was busy adopting new implementing legislation setting maximum levels for the sum of dioxins and dioxin-like polychlorinated biphenyls (PCBs) in food and feed.

Maximum levels for dioxins in food of animal origin and all animal feed have been applicable since July 2002. Howeverdue to lack of sufficient data and scientific information at the timeno levels were set for dioxin-like PCBs.

Since 2002new data on dioxin-like PCBs has become availableand the new legislation lays down mandatory limits for the combined level of dioxins and dioxin-like PCBs.

From November 2006any food or feed in which the sum of dioxins and dioxin-like PCBs exceeds these maximum levels will not be allowed to be marketed in the EU.

The reduction of persistent chemicals such as dioxins and dioxin-like PCBs in the food chain is an important part of ensuring the health and safety of EU consumers.
It is likely that the Commission will shortly adopt recommendations that set ‘action levels’ and foresee ‘target levels’ for dioxins in feed and food.