The accident sensitized Gurjar, too, to the dangers of airborne contaminants. He thus set up a risk assessment study in which he compared the cancer rates in certain Indian states with the levels of potentially carcinogenic substances recorded by the local environmental authorities.
On the very day on which he was awarded his doctorate from the IIT in New Delhi, Gurjar learned from a scientist from the US that Jos Lelieveld was recruiting postdoctoral researchers for his department. The group specialized in atmospheric chemistry, and Lelieveld himself had studied the interrelationship between atmospheric chemistry and climate. He investigated the effects of the Indian monsoon on pollution transports and the capacityof the atmosphere to clean itself and remove the contaminants.
Gurjar applied and was accepted for a three-year postdoctoral research scientist’s position – but he encountered a dilemma. He simultaneously had an offer for a Ford Foundation fellowship for studies at the Harvard School of Public Health. Gurjar recalls that Lelieveld sent him a single-page analysis in a leading scientific journal that pointed out that the Max Planck Society had more publications in the field of atmospheric chemistry than Harvard. He now admits that there was another reason he picked Germany over Harvard. The Ford Foundation fellowship was just enough for him to travel alone to the US. The pay as a post doc at the Max Planck Institute for Chemistry was also sufficient to bring his wife along to Germany.
When he arrived in Mainz, Lelieveld offered him the chance to choose any research topic he liked. “That was something of a surprise,” says Gurjar. In India, it is usual for a mentor to tactfully but firmly direct his protégés toward a particular subject. “I decided to study the air pollution in megacities, and Lelieveld evidently shared my enthusiasm for the topic.”
The importance of megacities, they both believed, would steadily increase, not least in research. And indeed the number of conurbations with more than ten million inhabitants has risen from just 2 in 1950, when only Tokyo and New York passed this threshold, to 20 at the beginning of the 21st century. According to some forecasts, the number of city dwellers worldwide will reach five billion by 2030, by which time 8 out of 10 megacities will be found in Asia and Africa.
As a consequence of this development, more and more people will be breathing air that is hazardous to their health. The problems vary from city to city. Every megacity is shrouded in its own characteristic air pollution, generated by high traffic densities and various industrial activities. In varying proportions, the air contains considerablequantities of carbon monoxide, sulfur dioxide, oxides of nitrogen, particulates – such as soot – and organic compounds such as those released in the combustion of fossil fuels. Some megacities generate more exhaust fumes than entire countries. In Beijing, for example, a total of 2.7 million tons of carbon monoxide are released into the air – more than Portugal – yet Beijing occupies only a fifth of the area covered by Portugal.
The resulting concentrations of exhaust fumes are certainly not conducive to good health. They have long been associated with respiratory diseases such as asthma, but in recent years, links have been established between air pollution and other illnesses ranging from cardiovascular diseases to breast cancer.
Five years ago, researchers at the University of New York, Mount Sinai School of Medicine and the University of Michigan produced results indicating that particulates with a diameter of 2.5 micrometers can cause arteriosclerosis, which in turn is a risk factor for heart disease. Scientists at the Fritz Haber Institute of the Max Planck Society reported two years ago that particulates less than 20 nanometers in size can provoke even greater inflammation than larger micro-particles. And just recently, experts at the Institute for Cancer Epidemiology in Copenhagen showed that long-term exposure to even low levels of air pollution increases the risk of serious chronic obstructive pulmonary disease, an affliction that makes it hard to breathe.
It is becoming steadily clearer that there is a risk associated not just with highly polluted air, to which even short-term exposure can be harmful. Even low concentrations of contaminants can cause damage if individuals are exposed to them over long periods. As an analogy, one could compare this with the passive smoking of cigarettes.