Epidemiologic Studies on Short-Term Effects of Low Levels of Major Ambient Air Pollution Components

Abstract

Since the development of the World Health Organization (WHO) Air Quality Guidelines for Europe, a large number of epidemiologic studies have been published documenting effects of major air pollutants on health at concentrations below existing guidelines and standards. In this review, recent studies are discussed that permit some evaluation of short-term health effects observed at exposure levels lower than the current WHO Guidelines or U.S. Environmental Protection Agency (U.S. EPA) standards. Some studies have been conducted at concentration levels that never exceeded existing guidelines or standards. Other studies have been conducted at exposure levels sometimes exceeding current guidelines or standards. The published analyses of several of these studies permit evaluation of low-level health effects either because analyses were restricted to levels not exceeding the guidelines or graphic analyses were reported suggesting effects at these low levels. For ambient ozone, effects on lung function of subjects exercising outdoors have now been documented at 1-hr maximum levels not exceeding 120 pg/m3, i.e., half the current U.S. EPA standard. One study even suggests that such effects occur at levels below 100 pg/m3. Several studies are now available documenting effects of particulate air pollution on health in the virtual absence of SOL. Effects on mortality and hospital admissions for asthma have been documented at levels not exceeding 100 pg/m3, expressed as 24-hr average inhalable particles PM10 concentration. Effects on lung function, acute respiratory symptoms, and medication use have been found at 24-hr average PM10 levels not exceeding 115 pg/m3. When the WHO Air Quality Guidelines and the U.S. EPA standard for PM10 were developed, there were no studies available on health effects of PM10. In this review, we include nine studies documenting health effects of measured PM1 0 at low levels of exposure, indicating that there is now an entirely new epidemiologic database that can be evaluated in the process of revising current guidelines and standards. The low levels of exposure at which effects on health were seen underscore the urgent need for such reevaluations. -Environ Health Perspect 1 03(Suppl 2): 3-13 (1995)

Environmental factors and hospitalisation for chronic obstructive pulmonary disease in a rural county of England

“…We acknowledge that concentrations may vary markedly over a small geographic range and indoor and outdoor exposure can be very different 13 33. Furthermore, exposures will be influenced by individual activity patterns 13. Similarly, this study did not assess the effect of one or more pollutants in combination.…”

“…In common with other studies, we were not able to measure personal exposure to pollutants, but rather relied upon ambient concentrations. We acknowledge that concentrations may vary markedly over a small geographic range and indoor and outdoor exposure can be very different 13 33. Furthermore, exposures will be influenced by individual activity patterns 13.…”

“…The framework was modelled using binary logistic regression, where the outcome was coded 1 for admission days and 0 for control days, and the explanatory variables were the environmental variables and influenza incidence recorded for each corresponding day. Control days relatively close in time to the event day reduce confounding due to seasonal effects and slowly changing patient characteristics, such as deterioration of lung function over time 13 18. Seven days between the case and control observations ensured that the control observations were sufficiently distant from admission to have been unlikely to have affected lung function.…”

“…However, it is thought that airborne pollutants interact with infections to produce inflammation of the lower respiratory tract,10 and the resultant inflammatory response worsens the patient’s symptoms. Particulates (PM 10 ), sulphur dioxide (SO 2 ), oxides of nitrogen (NO X ) and ozone (O 3 ) have been shown to induce airway inflammation both in healthy individuals and in those with pre-existing allergic lung disease 10 – 13…”

“…This is because, with the exception of ozone, pollution levels are generally higher in large cities. A meta-analysis by Brunekreef et al 13 and work by Næss et al 20 in Oslo, among others, raise questions around the existence of thresholds for health effects of some air pollutants. It is not clear if COPD patients living in less urbanised areas will be impacted by changes in air quality in the same way as patients in large conurbations.…”