Abstract: An estimate of the health value of air pollution is provided in Life Ahead for orientation purposes. This shows that despite enormous publicity and public cost, the effect of air pollution on health and life is small compared with that from even small changes in our life style habits. As shown elsewhere, the effect of passive smoking - the risk conveyed from the cigarette smoking of others - appears potentially larger than that of other atmospheric pollution.
Background: Air Pollution has been given enormous amount of publicity during the past several decades. Massive costs have been dedicated to the reduction of industrial pollutants, and air today in US and many world industrialized areas probably is far cleaner than it was at any time during the past century. Yet many people still are concerned about the effect of present atmospheric pollution on their health. Although pollution is regarded as a largely “Non-actionable” factor of health, it was felt desirable to included some valuation of how this might effect our overall health and life in the Life Ahead Model.
Many pollutants combine in the measure of 'Atmospheric Pollution'. These include particulates of various size, sulfur dioxide, nitric oxide, carbon monoxide, dusts, and toxic metals. But relationships of these agents generally have been measured from overall correlations of each with disease and death. Particle pollution appears to have been best correlated with rates of death, and a measure of fine particle pollution called PM2.5 has been used in the study that follows. This will be far from a perfect index of the individual effects of all individual pollutants, but still probable produces a useful measure of overall harm.
The Research Study: The Life Ahead Pollution Analysis was based on a recent and very sophisticated study of Pope, et al JAMA 2002:287:1132. This study of 1.2 million US adults initiated in 1982 followed results on 500,000 individuals in 53 metropolitan areas in which Fine Particulate Air Pollution was measured. The results were risk ratio (RR) values for all-cause death, cardiopulmonary death, lung cancer death, and all other cause death associated with a measure of fine particles in the atmosphere called PM2.5.
It was found not surprisingly that pollutants in the 53 areas were about 30% lower in 1999-2000 than they were in 1979-83. The more recent range of PM values in these areas was from about 5 to 18 on the scale used. This information was adapted to Life Ahead by using values of 5 for “Rural”; 11 for “Suburban”, 15 for Suburban-Urban, and 18 for Urban-Industrial as categories of entry.
The Valuation in Life Ahead: The key factors used from this analysis were a risk ratio for all-cause Death of 1.06 (CI = 1.02-1.10), and a risk ratio for lung cancer death of 1.13 (CI = 1.04-1.22) for a difference of 10 units in PM. These values were translated to 1.08 and 1.17 respectively for the overall Rural-Urban-Industrial difference in PM for 13 units. The overall RR values of all-cause death for this difference of 13 PM were equivalent to that of an added Life Ahead entry of 0.9 cigarettes per day. Or by category, an equivalent of 0.2 cigarettes/day for rural, 0.6 for suburban, 0.9 for Suburban-Urban, and 1.1 for Urban Industrial closely reproduced the amounts of all-cause death described by this study. The Air Pollution risks were valued via Life Ahead assuming a duration of contact throughout most of life, and not starting only at a starting age of smoking.
The death rate risk ratio for lung cancer from Air Pollution was only slightly higher than that for all-cause death. In contrast the lung cancer death rate frisk rom smoking is far higher than the all-cause risk of death rate. This same lesser effect on lung cancer was noted in the research on passive smoking, the smoke of others that smoke. This suggests that atmospheric pollutants will not produce the same effects on disease was do cigarettes. Perhaps some of the harmful components of cigarettes such as carcinogenic tars that go directly into the lungs from cigarettes either drop out or are modified before intake from a usual atmosphere. The effect of pollution on lung cancer is thus modified in the Life Ahead model to agree more closely with these actually measured effects. The above effects of Air Pollution on major disease and death are roughly consistent with those included in the earlier 1985 Life Ahead model from a quite different research data.
Life Ahead computes the effect of Air Pollution sequentially to and via the same method used for Passive Smoking. The base disease and death rates for the non-smoking US population for all diseases at all ages are adjusted via the Smoking module [prior to adjustments for other factors, but using the above values for cigarettes per day plus some modification of effects by disease.
The Effect of Air Pollution on Life: The Life Ahead computes for an average US population of age 50 a difference of 250 Well-Days between the highest and lowest usually measured levels of Air Pollution. The estimated difference between Suburban and Urban-Industrial levels is 110 Well-Days. These differences in health although significant are smaller than those associated with passive smoking. And they are small compared with benefits that result from even minor differences in long term diet, exercise and other lifestyle habits. Air pollution of course can cause a variety of other non-lethal health problems not included in this analysis. And because the effects of air pollution probably apply to nearly everyone in our population its gross effect on population health can be quite substantial.
The effect of Air Pollution on various major diseases is noted in the Life Ahead results together with the effect of passive smoking as supplementary "Non-actionable" health factors that could increase the incentive for maintaining good health habits.