Air Pollution Ozone

4. Should current O₃ guidelines be reconsidered?

• 4.1 Have positive impacts on public health of Ozone reductions been shown?
• 4.2 Averaging period most relevant for Ozone standards to protect human health
• 4.3 Reconsideration of the current WHO Guidelines for Ozone

4.1 Have positive impacts on public health of Ozone reductions been shown?

See also our Digest on Respiratory Diseases in Children

"There are very few opportunities to evaluate O₃ reduction per se. One study of intra-state migrants showed a beneficial effect on lung function in children who moved to lower PM and O₃ areas. A decrease in O₃ during the 1996 Olympics was associated with a reduction of asthma admissions. The interpretation of these findings is unclear." More...

Source & ©: WHO Europe  "Health Aspects of Air Pollution" (2003) Section 6.2

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

"For short-term exposure, it is clear that the effects increase over multiple hours (e.g., 6–8 hours for respiratory function effects and lung inflammation). Thus, an 8-hour averaging time is preferable to a 1 hour averaging time. The relationship between long term O₃ exposure and health effects is not yet sufficiently understood to allow for establishing a long-term guideline." More...

Source & ©: WHO Europe  "Health Aspects of Air Pollution" (2003) Section 6.2

4.3 Reconsideration of the current WHO Guidelines for Ozone

"The current WHO Air quality guidelines (AQG) (WHO, 2000) for O₃ provide a guideline value of 120µg/m³ (60 ppb), based on controlled human exposure studies, for a maximum 8-hour concentration. The AQG also provide two concentration-response tables, one for health effects estimated from controlled human exposure studies and one from epidemiological studies. No guideline for long-term effects was provided. Since the time these guidelines were agreed, there is sufficient [new] evidence for their reconsideration. Issues to be considered are: the averaging time(s) for the short-term guidelines and their associated levels, the [concentration-response] functions used in the tables, the outcomes included in the concentration-response tables, whether a long-term guideline and/or complementary guidelines (e.g. restricting personal activity) should be adopted.

Recent epidemiological studies have strengthened the evidence that there are short-term O₃ effects on mortality and respiratory morbidity and provided further information on exposure-response relationships and effect modification. There is new epidemiological evidence on long-term O₃ effects and experimental evidence on lung damage and inflammatory responses. There is also new information on the relationship between [ambient concentrations measured by] fixed site ambient monitors and [total] personal exposure, which affects the interpretation of epidemiological results." More...

Source & ©: WHO Europe  "Health Aspects of Air Pollution" (2003) Section 6.2