New look at cancer causes

Environmental causes of cancer are coming under scrutiny by the Cancer Association of South Africa (Cansa) in an attempt to reduce the burden of this disease among South Africans.

The cancer NGO will be expanding research into common carcinogens found in food and the environment as part of its campaign to educate consumers and lobby government and business.

The move follows a recognition that environmental factors may contribute to about 90% of all cancers. Genetic factors are only thought to account for 10%.

Cancers are caused by a complicated multi-stage process, and contributors include chemicals, viral and bacterial infections and ultra­violet light. Cansa estimates that about 30% of cancers are caused by cigarette smoke, 15% by diet, between 10% and 20% by pollution, and the same amount by infections.

Cansa director Carl Albrecht said part of the organisation’s new strategy would be to buy samples of food and goods from retailers and send them for analysis to reputable agencies such as the Council for Scientific and Industrial Research.

The aim is to check for chemicals known or strongly suspected to be carcinogens and then post the results on the Cansa website.

“We are shedding light on an aspect of cancer-causing and possible ­cancer-causing products,” said Albrecht.

Cansa has a research budget of about R5-million a year, which comes from a research investment fund. It receives no government funding, relying instead on donations from individuals and organisations.

High on its agenda is encouraging the government to ban the use of a chemical Bisphenol A (BPA) as an ingredient in plastic baby bottles. In April this year the Canadian government banned BPA from use in baby bottles after labelling the chemical “toxic”.

Albrecht says the government should follow the Canadian lead. “There is no reason to believe bottles are any different, or babies are any different here compared to Canada,” he said.

BPA was invented in 1891 and mimics oestrogen to the extent that it was once investigated as a synthetic substitute for the naturally occurring hormone.

“Effectively we have baby bottles made from a hormone,” said Albrecht.

Cansa says that over the past nine years more than 100 publications have linked BPA to a range of health problems, including prostate damage, reduction in testosterone, early puberty and potentially cancerous changes to breast and prostate cells.

Used in food and drink containers, BPA migrates into the contents of the container. Cansa says that using boiling water in polycarbonate water bottles—such as baby bottles—can increase this migration of BPA up to 55 times.

Another of Cansa’s diet-related prevention strategies is to identify food with trans-fats—plant oils that have been treated to break chemical bonds and convert them into semi-solids. They are commonly used in margarines, confectionary and baking shortenings. Cansa says that consumption of trans-fats increases the risk of coronary heart disease and has been implicated in the biological processes that increase risks of other health problems such as diabetes and weight gain.

Although some countries, including the United States, require food labels to show any trans-fat content, similar legislation in South Africa has not moved forward since July 2007.

Cansa is calling for these regulations to be implemented, along with a range of other measures such as lobbying fast food businesses to stop using trans-fats in their products.

Plasticisers—chemicals that give increased flexibility and durability to plastics such as cling film—are also among the food-related products targeted by Cansa.

Some plasticisers move from the cling film into the food it covers and the process is speeded up when the plastic is heated—for example when defrosting chicken in a microwave.

Cansa says that two chemicals in particular, DEHP and DEHA, have been linked to biological damage, including decreasing testosterone levels, and possibly, early puberty in girls.

DEHP and DEHA are fairly ubiquitous and are found in a range of products including children’s toys, cling films, shampoos, perfumes and even sex toys.

Cansa would like to see these chemicals banned from children’s soft toys and cling film used on food.

Non-food-related environmental factors are also high on Cansa’s agenda Albrecht said that, for example, the Wonderboomspruit catchment area, which stretches between Johannesburg and Potchefstroom, is polluted with uranium and cadmium as a result of gold mining. About 400 000 people live in the area.

Cansa emphasises that levels of contamination with uranium, a weakly radioactive metal, are particularly problematic in this area of South Africa’s mining heartland, saying that “uranium salts could be formed in acidic slime dams and tailings of the goldmines, enter the irrigation systems and end up by contaminating food eaten by the people”.

Cadmium, another heavy metal, has been linked with cancers of the bladder, lung, breast, pancreas and kidneys.

Albrecht said: “Both government and the mines profited tremendously from what’s going on there. Why they haven’t put back into the environment I don’t know.”

Cansa is calling for the relevant government departments and the nuclear regulator to prevent people living in the area from coming in contact with cadmium and uranium.

The haze that fills the air in some areas of South Africa is another priority in Cansa’s lobbying and research agenda. The organisation says the smoke from burning wood, coal and petrol contains known carcinogens.

This is particularly problematic given the millions of South Africans who are exposed to such smoke in poorly ventilated huts and shacks.

In the case of environmental hazards such as uranium and smoke, Cansa says that there is a need for more local research to understand the impact on humans.

Particularly useful would be cancer maps to identify geographical or time-linked changes in cancer levels in areas such as Wonderboomspruit, where people are living in areas of high exposure to potential carcinogens.

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