After Kate Canada had her first child three years ago, phthalates was the chemical that health-conscious moms like her went out of their way to avoid. So she tossed the plastic toys and replaced them with wooden ones.

When she had a second daughter this year, BPA became the substance to fear. So she bought new baby bottles and got vigilant about stocking her pantry with all things BPA-free.

Then, a few weeks ago, she heard about an annual report from the President’s Cancer Panel that, for the first time, painted a dire picture about potential cancer risks from a legion of environmental hazards. At that point, she threw up her hands.

“Parents shouldn’t have to be chemists and shouldn’t have to worry about every little thing,” said Canada, 34, of Rodgers Forge. “It just seems to be never-ending. It’s like, what’s next?”

The panel’s 240-page report urging more research and stronger regulations to protect the public from environmental chemicals that could cause cancer validated the work of scientists and environmental advocates who have long pressed for such safeguards. The three-member panel noted that people should limit their exposure to potential problem items such as pesticides, medical X-rays, plastic food containers and industrial chemicals. But with everything from drinking water to canned goods suspected as a threat, how should people try to limit these exposures? Or should they even bother?

Not everyone agrees that chemicals in the environment pose an urgent cancer threat. The American Cancer Society took issue with the panel’s statement that environmental exposures have been “grossly underestimated,” saying that the report is “unbalanced” in its implication that pollutants are a major cause of cancer. The organization feared the panel dismissed the notion that many more cancers are caused by lifestyle choices such as smoking and obesity. Cancer epidemiologists tend to agree.

“I do think we need to pay attention to environmental exposures, but compared to the very defined cancer risk factors, environmental exposures are pretty minor,” said Dr. Kevin Cullen, director of the University of Maryland’s Greenebaum Cancer Center. “The mistake would be to have people panic and make major changes around their lives and ignore other issues such as obesity and smoking.”

Consider that smoking accounts for about 30 percent of cancer deaths, while environmental exposure might account for as little as 5 percent, he said.

But Dr. Lynn Goldman, a professor of environmental sciences at the Johns Hopkins University’s Bloomberg School of Public Health, says people can and should focus on major causes of cancer, as well as limit their exposures to toxic substances.