One of the hardest things to do in science is to make the link between poisonous substances in the environment and consequences to human health.

When several local industries dumped toxic chemicals in the suburban Boston town of Woburn, for example, it took researchers years to connect the chemicals to the neighborhood's water supplies and then to the many cases of childhood leukemia in the community. And even then, Harvard School of Public Health scientists could only make what they called an "association" between the chemicals and the children's health problems.

That those links are hard to make is not lost on the sponsors of a study whose results were released this week. The sponsors, collectively called the Alliance for a Clean and Healthy Maine, represent a range of environmental, labor and public health groups.

Their first-ever study, "Body of Evidence," documented the presence of dozens of toxic chemicals in the bodies of the 13 Maine residents who were tested. Scientists found a total of 46 different chemicals -- normally found in common household items such as shower curtains, makeup, toys and water bottles -- by analyzing blood, hair and urine samples.

The study determined that, on average, each of the participants had measurable levels of 36 toxic chemicals in their body. Those chemicals -- among them phthalates, which are found in cosmetics and vinyl products; brominated flame retardants used in television sets; bisphenol A used in baby and water bottles -- have all been associated with various negative health effects, from male reproductive damage to birth defects, brain damage and chronic diseases.

On a visceral level, it wasn't pretty news. It appeared that what scientists found was a case of chemical trespass on the bodies of these Mainers.

Yet study authors acknowledge that, "Exposure pathways are difficult to establish ... moving from the sources of chemicals inside us to what effects they might have on our health is a formidable, sometimes impossible task for environmental health professionals."

Nevertheless, they write, "absence of knowledge is not proof of safety. The findings ... in this report ... beg us to err on the side of caution."

We've long known that chemicals in the air and in our water can harm us and other creatures on the earth -- that's why we have laws like the Clean Air and Clean Water Acts. They regulate what substances can be safely put into the country's skies and waters.

What we don't have are federal or state laws that require manufacturers to demonstrate the safety of a chemical before it is added to consumer products. There are no laws requiring manufacturers to substitute safer alternatives for more hazardous alternatives. Given that we are beginning to understand that at least some chemicals do migrate out of the consumer products in which they're found, the study sponsors recommend that the most harmful chemicals be phased out in favor of alternatives; that manufacturers be required to provide health and safety data on all chemicals and to disclose which hazardous chemicals are in what products; and that Maine invest in more environmentally friendly chemistry research and development, such as making bio-based plastics from Maine agricultural crops.

The proposals have obvious merit, though they represent an ambitious, world-altering agenda, much of which should be debated at the federal level.

In the meantime, there is action that can be taken in Maine.

In 2006, Gov. John Baldacci created the 13-member Task Force to Promote Safer Chemicals in Consumer Products, with representatives from Maine industry, environmental and public health groups, government, academia and labor. That group was assigned the job of creating a comprehensive chemicals policy for Maine. The coalition of groups that sponsored the recent report has done a major public service by alerting Maine citizens to the potential hazards literally in their midst -- and thus creating a constituency whose support will be essential for the task force to propose bold action.