GENERAL ARTICLES CURRENT SCIENCE, VOL. 87, NO. 6, 25 SEPTEMBER 2004 741 The authors are in the Environmental Impact Assessment Division, Salim Ali Centre for Ornithology and Natural History, Anaikatty, Coimbatore 641 108, India. *For correspondence. (e-mail: azeezpa@yahoo.co.uk) Health effects of airborne particulate matter and the Indian scenario R. Mohanraj and P. A. Azeez* Airborne suspended particulate matter (SPM) is a serious worldwide concern since it is linked with adverse health effects. Several epidemiological studies have been made across the world revealing the association of SPM in air with acute and chronic respiratory disorders, lung cancer, morbidity and mortality. Odds ratio estimated by several studies of the dose–response relationship for parti- culate matter (PM)-associated respiratory sickness and premature mortality, increased with rise in PM levels. Associations have been found with cardiovascular deaths, with myocardial infarctions and ventricular fibrillation. PM is also associated with autonomic function of the heart, including increased heart-rate, decreased heart-rate variability and increased cardiac arrythmias. Such health disorders are widely seen in urban areas worldwide that suffer from serious air-quality problems due to increasing population, combined with change in land use and vehicular traffic. In India, haphazard urbanization, unprecedented vehicular emissions and inadequate infrastructure development are supplementary factors for the fall in air-quality. Challenge for the future genera- tion in India lies in grappling the menace of air pollution-induced diseases, where already the pub- lic health is in a worrying state with a variety of diseases. This article attempts a brief review of atmospheric PM, its inhalation, deposition and toxicity, with experiences from the western coun- tries and the current Indian scenario. AMONG the variety of factors influencing health of an in- dividual, natural elements (the air we breathe, the water we drink, the radiation we are exposed to, etc.) and man- made environmental modifications (habitat, place of work, transport, industry and other development activities) play a crucial role. Chemical agents that are released into the environment from various anthropogenic activities impact human health seriously. The respiratory system is one major route whereby these chemicals and toxic agents en- ter the body and cause disorders, including mortality. On a global scale, millions suffer from respiratory ailments and other diseases attributed to the presence of toxic che- micals and biological agents in the air 1 . Although concen- tration of any pollutant in the environment is a quanti- tative expression of the presence of the pollutant, there is no exposure unless there is physical contact with human beings 2 . Exposure denotes the event when a person comes into contact with a pollutant for a particular time. On the other hand, dose refers to the actual quantity of pollutant that crosses the barrier of a body. Airborne particulate matter (PM) is the recent focus of the world community as it penetrates the respiratory system of human beings and causes many disorders. In the case of PM it is belie- ved that aerodynamic size, number and quantity of PM in the atmosphere play a vital role in impacting human health. It has also been shown through worldwide studies that the urban population is at risk due to elevated levels of PM in the urban atmosphere. Several time series and cohort studies have shown that children, elderly and asth- matic people are at higher risk due to air pollution. This article is an overview of outdoor air particulates and their impact on human health effects. Particulate matter Suspended particulate matter (SPM) refers to the mixture of solid and liquid particles in air. In a broader sense the term applies to matter in the atmosphere classed into parti- cles having a lower size limit of the order of 10 –3 μm and an upper limit of 100 μm. SPM, a complex mixture of organic and inorganic substances, is a ubiquitous air- pollutant, arising from both natural and anthropogenic sources. Ever since the advent of the industrial era, an- thropogenic sources of PM have been increasing rapidly. PM that is 10 μm or less in diameter is called as respir- able suspended particulate matter (RSPM) or PM10, since it penetrates the respiratory system. RSPM is generally grouped into three modes: ultra fine (size range less than