A new Canadian Cancer Society handbook available online details the environmental substances known to or suspected of causing cancer, and what can be done to limit exposure.

The Environment, Cancer and You handbook discusses asbestos, radon gas, electromagnetic fields, flame retardants, labelling of consumer products, phthalates in plastics, Teflon and non-stick cookware, and water chlorination byproducts.

"We know now, more than ever, that Canadians are concerned about the environment and cancer," said Heather Logan, the society's director of cancer control policy and information. "And we wanted to provide a resource that was clear, comprehensive and really understandable to give people practical advice to reduce their exposure to cancer-causing substances in the environment."

The online resource, available in English and French, explains that asbestos and radon gas increase a person's risk of developing lung cancer, in particular, and what steps Canadians can take to determine if they're at risk for exposure and how to prevent it.

Radon, for example, is a colourless, odourless radioactive gas released through the natural decay of uranium in rocks and soil. Some areas in Canada are at higher risk of exposure to radon gas, which can seep into homes and other buildings through the basement and contaminate indoor dust particles in the air.

Taking precautions

The handbook also points out other agents or phenomena the society considers of possible concern, such as electromagnetic fields from power lines, despite the absence of definitive scientific evidence.

"People have the right to know what the science tells us, what they can do if they choose to reduce their risk, even if the science is unclear," Logan said. "If they want to be as precautionary as they can, we're providing some of that information to take the most proactive steps that they can, if they want to.

"Where the science is really clear, our recommendations are much more precise."

Because the handbook is presented online, it can be quickly updated as new scientific evidence comes available, she said.

Environmental agents are only one piece of the puzzle when it comes to what causes the many types of cancer.

An individual's genetic makeup and exposure to pathogens (such as the human papilloma virus, which causes a high percentage of cervical cancers) also are determining factors.

"I think it's fair to say that the current estimate, the current available evidence around environmental exposure and cancer risk, and determining what proportion of cancer is attributable to the environment, is probably lower than it actually is," she said.

"What the actual number is, we just don't have firm enough evidence to say that."