PACKED off. A stunning US study has clinched the battle of evidence on what tiny particles in the air, mostly emitted by the combustion of fossil fuels do to human health. The industry had refused to admit the mounting scientific evidence that had emerged till now. But this study has come up with conclusive evidence. And has practically put the debate to rest.
A mere increase of 10 microgrammes per cubic metre (g/cum) of fine particles (smaller than 2.5 microns or PM2.5) can increase the risk of lung cancer by 8 per cent, cardiopulmonary deaths by 6 per cent and all deaths by 4 per cent. This shocking news was broken by a recent study published in the Journal of American Medical Association (JAMA).
Sixteen years, about 500,000 people and 116 metropolitan areas. That's what it took the researchers to come up with the findings. The analysis is based on data collected by the American Cancer Society (ACS) as part of the cancer prevention study II, an ongoing prospective mortality study of approximately 1.2 million adults.
"The findings of this study provide the strongest evidence to date that long-term exposure to air pollution, common to many metropolitan areas in the US, is an important risk factor for cardiopulmonary and lung cancer mortality," says Arden Pope, professor of economics at the Brigham Young University and co-author of the study. "To understand how air pollution might increase the risk for lung cancer, we first had to account for the effects of smoking on lung cancer risk," Pope adds.
The study has evoked strong response in the US. These findings come at a time when the George Bush administration attempts to dilute fuel effciency norms for vehicles. Environmental groups have seized on the new findings as support for their position that tough enforcement is still needed.
Allen Dearry, a scientist at the National Institute of Environmental Health Sciences, which partly funded the study, called it "the best epidemiologic evidence that we have so far that associates this type of exposure to lung cancer death."
John Kirkwood, president and CEO of the American Lung Association, said the study adds urgency to the need for the US Environment Protection Agency (USEPA) to immediately implement stringent new rules to curb fine particle emissions.
"This research dramatically underscores the urgent need for USEPA to limit the emission of these cancer causing particles," said Kirkwood. "The scientific evidence keeps mounting."
Pope teamed with Harvard researchers to report similar risks associated with cardiopulmonary mortality and fine particulate matter in two studies published in the mid-1990s. Automobile and manufacturing industry groups attacked the research as faulty science and their scorn grew when the USEPA used the studies as the basis for tightening particulate pollution standards in 1997 (see box: The business...). In addition to the new insights into lung cancer risk, Pope believes the new study's main contribution is putting to rest many of the detractors' claims.
Many US cities at present exceed that standard, though particulate air pollution levels have fallen considerably since 1979, the earliest year covered by the current study. According to the study, from 1979 to 1983, the annual average was 24 g/cum in New York City, 27 g/cum in Los Angeles, 23 g/cum in Chicago and 26 g/cum in Washington DC. The levels have come down over the years, and in 1999-2000 the annual average was 16 g/cum in New York, 20 g/cum in Los Angeles, 18 g/cum in Chicago and 15 g/cum in Washington, DC.
Despite this improvement, the study shows that current US levels of fine particulate matter air pollution are still high enough to be associated with a significantly increased risk of cancer and cardiopulmonary deaths.
In a way the study isn't saying anything new. It only reinforces what worldwide research in recent years was coming around: particulates are a big threat to human health.
Six per cent of all deaths in Austria France and Switzerland are due to PM10 - more than 400deaths per year - half of which are due to vehicular emissions according to a WHO report of 1999.Vehicular pollution is also responsible for more than 250new cases of chronic bronchitis in adults more than 2900episodes of bronchitis in children and more than 5000asthma attacks. The number of people dying from air pollution was twice to those dying from traffic accidents. Lifespan of people in cities was reduced by 18 months.
Dirty cousins
Two things are common to Latin American countries and Indian cities: poor air quality and few health-impact studies. That's why studies conducted in those countries are pointers to what could be the situation in India. A study in Mexico City from 1990-1992 observed a six per cent increase in daily mortality associated with an increase of 100 g/cum of total suspended particulates. In Santiagoa 10 g/cum increase in PM10 led to a 0.6 per cent increase in mortality. For respiratory deathsit was a one per cent increase. A study in Sao Paulo found that an increase of 100 g/cum in 24-hour average PM10 ambient levels led to a 13 per cent increase in mortality among those above 65 years. Ominous signs for India.
Fine particulate have more surface area than the relatively larger particles. This makes them the ideal substrate for toxic chemicals which deposit and stick on to the surface of the particles. Often many of these chemicals are known carcinogens like polycyclic aromatic hydrocarbons (PAHs). As researchers from the Columbia School of Public Health New York University Medical Centre and some more health research institutes found out. In their study on Polish women in Krakow they concluded that PAHs deposited along with particles not only damage pregnant women and new born children but also have a bigger impact on foetus. They came to this conclusion by measuring the amount of PAHs bound to the DNA of maternal and umbilical white blood cells. Another study by the Harvard School of Public Health published in 2001 and conducted in Roxbury Massachusetts found more PAHs near diesel vehicles whose ultrafine particles carry the toxins to the respiratory system.
KOREAN MALAISE: A study conducted in three cities in Korea found respiratory diseases even when air pollution was below standards set by the government.
Studying fine fine particles must in no way ignore the threats from relatively coarse particles. Scientists studied the effect of particulates of different size fractions - from PM10 to PM2.5 - and several gaseous pollutants (sulphur dioxide, nitrogen dioxide, ozone and carbon monoxide) during 1985-1990 and 1992-1994. When the estimated effects of PM10 and one of the gaseous pollutants were determined concurrently the association between PM10 and health outcomes remained the same or became even stronger suggesting that PM has its own effect regardless of the presence of other pollutants. The study was sponsored by the Health Effects Institute.
The authors found that relative risks for PM10-2.5 were similar to those for PM2.5 and sometimes even higher. The finding of elevated and significant effects for PM10-2.5 suggests that there may still be a rationale to consider the health effects of the coarse fraction along with the fine fraction of PM.
Some of the most shocking discoveries are often accidental. Scientists at the Harvard School of Public Health and Dana-Farber Cancer Institute know it better. They stumbled upon a revelation while studying the health effects of exposure to particulates. In many cases gases like carbon monoxide were taking the blame when the real culprits were particulates - an issue that was earlier overlooked.
Scientists measured exposure to ozone, nitrogen dioxide, sulphur dioxide, carbon monoxide and fine particulate matter (PM2.5).Except for PM2.5 ambient concentrations did not reflect corresponding total exposures of a person for any of the pollutants. This shows that ambient fine particulates are suitable surrogates for personal exposure to PM2.5.
ELDERLY: A Canadian study sponsored by the Health Effects Institute in 2000 used three measures of particulate matter: coefficient of haze (COH)total sulphate and PM2.5. For each of the three particle measures investigators reported an association with mortality from respiratory diseases and other non-accidental deaths including diabetes. Additionally COH was associated with increases in cancer deaths; sulphate was associated with mortality from coronary artery disease and cardiovascular diseases. All associations were generally stronger for those above 65 years
.DISEASED: The researchers analysed people who died of cancer cardiovascular diseases and respiratory diseases. People with acute lower respiratory disease congestive heart failure and a combined group of any cardiovascular diseases died at higher rates for increases in each of the three particulate matter measures. Associations with COH and PM2.5 were reported for subjects with cancer chronic coronary artery disease and any coronary artery disease and effects of sulphate were shown for those with acute and chronic upper respiratory disease.
ASTHMATICS: A ten-year study in Chicago found that people with asthma had double the risk of a PM10-associated hospital admission and that people with heart failure had double the risk for PM 10-induced chronic obstructive pulmonary disease (COPD) admissions. Another project investigated the short-term health effects of particles in eight European cities. For each 10 g/cum increase in PM10asthma in children (less than 14 years old) increased by 1.2 per cent and by 1.1 per cent in those between 15 and 64 years of age. For those above 65 years COPD and asthma increased by 1 per cent and all respiratory diseases increased by 0.9 per cent.
DIABETICS: Particulates can increase the risk of heart disease for diabetics. In a study conducted in Cook county, Illinoisa, team of scientists from the Harvard School of Public Health looked at the association of PM10 with hospital admissions for heart and lung disease in persons with or without diabetes as co-morbidity. A 10g/cum increase in PM10 was linked with a 2.01 per cent increase in admissions for heart disease with diabetes but only a 0.94 per cent increase in persons without diabetes.
Particulate pollution and heart attacks. Three independent studies conducted in Utah, Baltimore and Boston tried to find a link. In the Utah study researchers from the University of North Carolina and Harvard University measured oxygen saturation and pulse rate of elderly residents during winter when particulate matter concentration is highest. In the Baltimore and Boston study researchers took 25 minutes of electrocardiogram measurements of people weekly.
In the Utah study researchers found a small elevation in pulse rate was associated with a rise in PM10 levels. Both the Baltimore and Boston studies found that elevated concentrations of fine particulate matter were associated with lower heart rate variability and that the association was stronger for people with cardiovascular disease. Low heart rate variability is a marker of poor cardiac control by autonomic nervous system and is associated with a higher risk of heart attacks and sudden cardiac deaths. The study was published in 1999-2000.
If you want your child to grow up with healthy lungs move to a lesser polluted location. Fast. Because polluted air can impede lung function in kids. Researchers from the National Institute of Environmental Health Sciences in North Carolina studied 110 ten-year-old children growing up to 15 years who shifted to different cities with different levels of air pollution. They found that changes in annual average exposure to PM10 were associated with differences in annual lung function growth rates. Kids who had moved to areas with lower PM10 showed increased growth in lung function and those that moved to areas with a higher PM10 showed decreased growth lung function.
In another study scientists conducted a two-year time-series analysis of daily visits to primary healthcare clinics in Santiago Chile for either upper or lower respiratory symptoms for children 3-15 years of age and below two years. The results show an association between PM10 and medical visits for both upper and lower respiratory symptoms in children aged 3-15 and in children under age two. For children under two a 50 g/cum change in PM10 was associated with a 4-12 per cent increase in lower respiratory symptoms. For children 3-15 years of age the increase in lower respiratory symptoms ranged from 3-9 per cent.
| ULTRAFINES have larger surface to carry more toxics; stay longer in air; and are more in number |
Particle diameter (m) |
Number of particles in 1g |
Surface area (m2/g) |
Settling velocity (cm/sec) |
| 0.01 | 2,000,000,000,000 | 6,000,000 | 0.000005 | |
| 0.1 | 2,000,000,000 | 600,000 | 0.00008 | |
| 1.0 | 2,000,000 | 60,000 | 0.0035 | |
| 2.5 | 120,000 | 24,000 | 0.02 | |
| 10 | 2,000 | 6,000 | 0.3 | |
| Source: P M Hext 1999, The Health Effects of PM 2.5 concawe, Brussels | ||||
Clearly these figures demand control of particulate emissions on a war footing. Yet the government has made its mark in dilly-dallying. It is yet to develop a proper emission source inventory. But international studies have proved beyond doubt that fine particles - the most lethal ones - come mainly from vehicles. The growing automobile fleet, particularly diesel vehicles, even in the smaller towns are becoming the biggest threats to public health.
This makes a national policy on controlling vehicular pollution imperative. Though the Union government constituted a national committee for recommending national auto fuel policy, its recommendations reflected an urgency to protect the market for dirty diesel and inferior petrol rather than to expedite introduction of cleaner fuels and technologies and clean up the air of the dying cities.
The committee showed its mettle in quibbling over whether to introduce Euro II or Euro III by 2005 in cities, which are not even the most critically polluted. The only city among the top ten polluted that is on the privileged list
prescribed by the committee is Delhi.
Despite massive exercises in emission control in western countries adverse health impacts are showing up even at very low levels of pollution. This put a question mark on the
conventional incremental approach of reducing emissions and led to a paradigm shift. The focus has shifted to alternative fuels and technologies and gradually to zero emission vehicles. While California moves from low emission vehicles to ultra to super ultra low emission vehicles, the European Union recently announced that even Euro V is certainly not the end of the road. It is even contemplating controlling the number of
particles emitted from vehicles. Caught in the quagmire of international progress and national lack of vision, the polluted lungs of the silent majority in India gasp for fresh air.