Air Pollution Particulate Matter

4. Should current PM guidelines be reconsidered?

• 4.1 Impacts on public health of PM reductions
• 4.2 Averaging period most relevant for PM standards to protect human health
• 4.3 Reconsideration of the current WHO Guidelines for PM

4.1 Impacts on public health of PM reductions

WHO states: "Positive impacts of reductions in ambient [PM] concentrations on public health have been shown in the past, after the introduction of clean air legislation. Such positive impacts have also been reported more recently in a limited number of studies. Toxicological findings also suggest that qualitative changes in PM composition could be of importance for the reduction of PM-induced adverse health effects." More...

Source & ©: WHO Europe (2003)

4.2 Averaging period most relevant for PM standards to protect human health

WHO states: "As effects have been observed from both short-term and long-term ambient PM exposures, short-term (24 hours) as well as long-term (annual average) guidelines are recommended." More...

Source & ©: WHO Europe (2003)

4.3 Reconsideration of the current WHO Guidelines for PM

WHO states: "The current WHO Air quality guidelines (AQG) provide exposure-response relationships describing the relation between ambient PM and various health endpoints. No specific guideline value was proposed as it was felt that a threshold could not be identified below which no adverse effects on health occurred. In recent years, a large body of new scientific evidence has emerged that has strengthened the link between ambient PM exposure and health effects (especially cardiovascular effects), justifying reconsideration of the current WHO PM Air quality guidelines and the underlying exposure-response relationships.

The present information shows that fine particles (commonly measured as PM_2.5) are strongly associated with mortality and other endpoints such as hospitalization for cardio-pulmonary disease, so that it is recommended that Air quality guidelines for PM_2.5 be further developed. Revision of the PM₁₀ WHO AQGs and continuation of PM₁₀ measurement is indicated for public health protection. A smaller body of evidence suggests that coarse [particle] mass (particles between 2.5 and 10 µm) also has some effects on health, so a separate guideline for coarse mass may be warranted. The value of black smoke as an indicator for traffic-related air pollution should also be re-evaluated."

Source & ©: WHO Europe (2003)

See also: General Issues and Recommendations on Air Pollutants:

• Question 5.3 on uncertainties in defining thresholds
• Question 7.1recommendations regarding the concept of threshold

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