I've just spent a week with a bunch of scientists, so I'm feeling pretty cautious about my statements. Uncertainty is a big issue: uncertain measurements, uncertain results, uncertain correlations between exposure and effect. Uncertainty can arise from statistical variation, from indeterminate results or from plain old ignorance of all factors. It's enough to make even the most ardent anti-toxics campaigner pause before yelling "Endocrine Disruptor!" in a crowded room.

On one topic it appears to me that there is no longer any reason for uncertainty: Air pollution is bad for your health. There is no need to discuss it anymore. Should there be more study to better understand some aspects? Sure, go ahead. Delaying strong and significant action is just not right.

Whether from particulate matter, poly-aromatic hydrocarbons, soy dust, or volatile gasses; whether generated by burning coal, bleaching pulp, running a grain elevator or driving your car; whether air pollution increases risks for asthma and other cardio-pulmonary diseases, it can lead to increased rates of hospitalization and death. There is enough specific information in the scientific literature for any politician or business leader to be convinced. It is time to act.

Add the emerging evidence that global warming, another result of air pollution, will contribute to the world,s burden of disease, and not taking action starts to look down-right criminal.

Canada needs mandatory targets for all the known contributors, be they industrial or domestic. Those targets need to be stringent and protective of the most vulnerable in society: children and the elderly. Time-lines to meet the targets need to be short, 5 years at the most. A certain amount of hardship to industry and individuals has to be accepted.

Most of all, we need to change the way we do business by thinking ahead and designing processes that are zero discharge and closed loop, right from the start.

Which brings me to the Precautionary Principle.

The Precautionary Principle (which, according to some debates at the conference, may actually be an Approach, a Rule-of-Thumb, or a specification of pre-existing principles from medicine and public health, depending on one's academic and philosophical peccadilloes) has four main points:

• It is often necessary to take action in the face of uncertainty
• The burden of proof must be reversed, ie. proponents of a potentially harmful activity bear the responsibility for proving its safety and researching the safest possible approach
• Open public participation is essential and all stakeholders must be supported in their efforts to participate
• All the alternatives need to be explored and analysed for their relative risks and benefits, including the option of not proceeding with a proposed activity.

The week long ISEE/ISEA meeting included a 3 1/4 hour symposium entitled "Environmental Exposures, Public Health and the Precautionary Principle." Clearly it is an issue of importance to the people who research exposure to environmental pollutants and the results of those exposures on people.

I came away with not just a better understanding of the complexities of defining and applying "precaution," but also a realization that this group is not the only one that needs the concept explained. People in the public health field already have many (if not all) of these ideas in the ethical principles that guide their work. "First, do no harm," is a well known example.

We need government policy makers and business leaders to understand, respect and implement a truly precautionary approach. There are many reasons this is true, but one of the most important is that a precautionary approach requires that, when assessing any new policy or technology, we must know who will derive the benefits and who will take the risks.

We must also know, and account for, all the uncertainty inherent in a decision without letting uncertainty be used as an excuse not to act.

Taking action in the face of uncertainty, making polluters prove their actions are safe, making sure the public can participate, analysing all potential alternatives for likely effects, and accounting for the societal distribution of risk and reward are all essential elements of the Precautionary Principle and essential roles of good government.

As Colin Soskolne, from University of Alberta and Raymond Neutra, from the California Department of Health Services, pointed out in their excellent presentations, scientists need to adopt precautionary thinking to make sure their research is relevant to good policy creation and governments need to develop democratic and forward-thinking strategies based on precaution and full stakeholder participation to ensure that the least vulnerable and the public interest are protected.

Perhaps the best summary of these responsibilities came from Nick Ashford, of the Massachusetts Institute of Technology, "Government can be a referee and the weak walk away with the crumbs, or government can implement policies in a trustee fashion to protect the public good."

Hear, hear!

Resources on the Precautionary Principle:

Lowell Conference: (The Home page and the links to Statement and Summary are especially useful)

Kriebel, D, J Tickner, P Epstein, J Lemons, R Levins, E Loechler, M Quinn, R Rudel, T Schettler and M Stoto. 2001, "The Precautionary Principle in Environmental Science," Environmental Health Perspectives 109: 871876.

ISEA/ISEE 2002 Symposium presentations 11.01-11.08, www.conferences.ubc.ca/iseaisee2002

Research notes From ISEA/ISEE 2002: a brief gleaning of emerging issues

Indoor concentrations of volatile organic compounds (VOCs), like toluene, benzene, and xylene, can actually increase in residences farther away from an industrial source, due to outdoor concentrations declining through dispersion. Jo et al, Evaluation of VOC Levels Relative to Proximity to Dyeing Industrial Complex, (43.05).

Existing levels of gaseous criteria air pollutants, even when lower than current US EPA standards, are suggested to have adverse health effects on cardiac autonomic control. Liao et al, Gaseous Criteria Air Pollutants Are Associated with Impaired Cardiac Autonomic Control, Pennsylvania State University College of Medicine. (45.08).

Poly Aromatic Hydrocarbons (PAHs): PAH results from all types of combustion. Exposure is linked to a variety of negative health effects, including cancer.

• PAHs react with enzymes and then link with DNA to produce mutations which lead to cancer. Erdmann, C.A. and R. Goth-Goldstein, Gene-Environment Interactions and Breast Cancer Risk: The Potential Role of Metabolic Enzymes and PAH Exposures, (49.01).
• Coal burning produces characteristic PAHs (methylated) that are carcinogenic and linked to some of the highest percentage of mutations ever recorded in a well studied set of genes. Lung cancer rates in the study group (non-smoking women in China) are 8 times the national average. DeMarini et al, Lung Tumor KRAS and TP53 Mutations in Non-Smokers Reflect Exposure to PAH-Rich Coal Combustion Emissions, (49.02).
• Specific PAH sources have properties, and will leave biomarkers in humans, that can identify the source of the exposure. Coal produces primarily methylated PAH and benzoflouranthene. Vegetative burning (including lignin) will be high in methoxyphenol and levoglucosan. Benzo(ghi)perylene is from gasoline exhaust. PAHs from pulp mills will be high in sulphates. Relative toxicity tools help researchers refine risks from various sources. Lewtas et al, Attribution of Particle Exposure and Risk to Combustion Source Emission Based on Personal PAH Exposure and Urinary Metabolites, (49.04)

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