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Children who live in close proximity to gas stations and auto body shops have a dramatically higher rate of leukemia, according to a new study.

The research, published in the journal Occupational and Environmental Medicine, provides powerful evidence that the common childhood cancer may be caused by exposure to the chemical benzene.

Benzene, used in the manufacture of paints, plastics and pesticides, is also present in gasoline fumes. Previously, exposure to the chemical has been linked to leukemia in adults, but this is the first time the link has been made to children.

Jacqueline Clavel, a researcher at the French National Institute of Health and Medical Research in Villejuif, said unleaded fuel -- which is the norm in Canada -- contains small amounts of benzene.

But she said this is deceiving because the air around gas stations may actually be more polluted than in industrial settings where the chemical is used, or in neighbourhoods where there are emissions from refineries.

"The benzene concentrations around petrol stations during refuelling may be relatively high compared to environmental background concentration," Dr. Clavel said.

To conduct the study, researchers examined the background of 280 children with acute childhood leukemia living in four large French cities -- Paris, Lyons, Lille and Nancy. Another 285 children of similar age and gender who did not have leukemia were studied for comparison purposes.

The scientists found that children living in proximity to gas stations and commercial garages were four times more likely to have developed leukemia. They were almost eight times as likely to have developed one specific form of the cancer, acute non-lymphocytic leukemia. The majority of children stricken by cancer were aged 2 to 6.

The longer a child lived near a gas station, the higher the risk, according to the study. The risk of developing leukemia increased by about 3 per cent per month, including time spent in utero.

The research did not reveal any increased cancer risk for children living in proximity to a host of other commercial and industrial enterprises such as plastic factories, printing plants, metal works and retail shops.

Nor was any link found between childhood leukemia and living in close proximity to high-traffic roads. Several other studies, however, have shown such an association, particularly in adults.

Dr. Clavel said researchers were careful to compare two groups of children from similar socioeconomic backgrounds because cancer is more prevalent among low-income groups.

Almost 1,300 children are diagnosed with cancer in Canada each year, and about 230 die, according to the National Cancer Institute of Canada. Almost one-third of the cases and the deaths are due to leukemia.

Overall, an estimated 3,900 Canadians will be diagnosed with leukemia in 2004, and 2,200 will die of the disease.

The causes of leukemia are largely unknown. What is known, however, is that exposure to radiation and certain types of chemotherapy can cause leukemia. Children with Down syndrome and certain other rare diseases such as ataxia-telangiectasia also have a much higher risk of developing the cancer that starts in white blood cells.