living in an environment polluted with even low levels of benzene can cause cancer. While exposure to benzene at work places have been known to cause cancer, a study published recently in the American Journal of Epidemiology shows that exposure to low concentrations of the chemical such as those present in vehicular emissions can also cause cancer.

Researchers from the Danish Cancer Society and the National Environmental Research Institute, Denmark, found that children exposed to traffic-related air pollution had more chances of being affected by lymphomas, a cancer of the lymphatic system characterised by enlargement of the lymph nodes and glands. The researchers studied 1,989 cases of children suffering from leukaemia, tumour of the central nervous system and malignant lymphoma that were registered in the Danish Cancer Registry during 1968-1991. The histories were compared with the medical records of 5,506 healthy children selected at random. They then collected the residential history of all these children starting from the time they were conceived till the time the disease was diagnosed. The information was used to assess the amount of vehicular pollution they were exposed to. They also took into consideration other potential causes of cancer such as exposure to electromagnetic radiation, mother's age at conception and level of urbanisation.

They found that the risk of Hodgkin's lymphoma increased by 25 per cent when the amount of benzene in the air was doubled during pregnancy. Similarly, the risk increased by 51 per cent when the nitrogen dioxide emissions present in the air doubled.

"This is a suggestive observation that will require confirmation,' says Lucy M Anderson of the National Cancer Institute, usa . Even Ole Raaschou-Nielson, one of the research team member, agrees. "We cannot rule out the fact that they might be numerous other factors which can be the culprits,' says Raaschou-Nielson.