November 19, 2011

Reviewing the air pollution death and health impact numbers and peer reviewed epidemiological studies

There was a World Bank 2007 study of the economic cost of air pollution on China (151 pages)

According to conservative estimates, the economic burden of premature mortality and morbidity associated with air pollution was 157.3 billion yuan in 2003, or 1.16 percent of GDP. This assumes that premature deaths are valued using the present value of per capita GDP over the remainder of the individual’s lifetime. If a premature death is valued using a value of a statistical life of 1 million yuan, reflecting people’s willingness to pay to avoid mortality risks, the damages associated with air pollution are 3.8 percent of GDP. These findings differ in two important ways from previous studies of the burden of outdoor air pollution in China. First, they are based on Chinese exposure-response functions, as well as on the international literature; and second, they are computed for individual cities and provinces. Previous estimates by WHO (Cohen et al. 2004) were based on the assumption that increases in PM beyond 100 micrograms/m3 of PM10 caused no additional health damage.( In the base case considered by WHO relative risk does not increase beyond 50 micrograms/m3 of PM2.5, which is approximately equivalent to
100 micrograms/m3 of PM10.) This assumption implies that the WHO estimates cannot be used to evaluate the benefits of specific urban air pollution control policies.

Two-thirds of the rural population is without piped water, which contributes to diarrheal disease and cancers of the digestive system. The cost of these health impacts, if valued using a VSL of 1 million, are 1.9 percent of rural GDP. Analysis of data from the 2003 National Health Survey indicates that two-thirds of the rural population does not have access to piped water. The relationship between access to piped water and the incidence of diarrheal disease in children under the age of
5 confirms this finding: the lack of access to piped water is significantly associated with excess cases of diarrheal disease and deaths due to diarrheal disease in children under 5 years of age.

Updated analysis of pollution costs for China have been made.

A combined paper by researchers from Harvard and Tsinghua universities in 2009 estimated air pollution alone contributed to health damages equivalent to 1.8 percent of GDP.

China, the world’s worst polluter, needs to spend at least 2 percent of gross domestic product a year -- 680 billion yuan at 2009 figures -- to clean up 30 years of industrial waste, said He Ping, chairman of the Washington-based International Fund for China’s Environment. Mun Sing Ho, a senior economist at Dale W. Jorgenson Associates and a visiting scholar at Harvard University in Cambridge, Massachusetts, put the range at 2 percent to 4 percent of GDP.

Failure to spend that much -- equivalent to the annual GDP of Vietnam -- may cost the Chinese economy half as much again in blighted crops, health costs and pollution-related expenses

In recent years, epidemiological studies conducted around the world have demonstrated that there are close associations between air pollution and health outcomes. PM10 and SO2 are chosen in many studies as the indicative pollutants for evaluating the health effects of ambient air pollution. Although the mechanisms are not fully understood, epidemiological evidence suggests that outdoor air pollution is a contributing cause of morbidity and mortality. Epidemiological studies have found consistent and coherent associations between air pollution and various outcomes, including respiratory symptoms, reduced lung function, chronic bronchitis, and mortality.

In China, epidemiological studies have been conducted beginning in the 1980s and 1990s in Beijing, Shenyang, Shanghai, and other cities. These include two time-series analyses of the relationship between daily air pollution and hospital outpatient visits/emergency room visits and daily cause specific population mortality in urban areas of Beijing (Chang et al. 2003; Chang, Wang, and Pan 2003), a meta analysis of exposure-response functions between air pollutants and cause-specific mortality derived from Chinese studies, and a regression analysis of environmental monitoring data and population mortality data for over 30 cities of China.

Causal Agents in Air-Pollution- Related Disease

Although adverse effects on human health from particulate matter, SO2, O3, NOx, and CO are documented, most studies have focused on the relationship between SO2, particulate matter, and respiratory and cardiovascular diseases. After thorough consideration, we decided to choose PM10 as the single air pollutant index for the following reasons:

1) Ambient SO2 concentrations in most Chinese cities have greatly decreased compared with a few years ago, and are in many cities now lower than the WHO Air Quality Guideline (2000) of 50μg/m3. The air quality monitoring results from Chinese cities in 2003 showed that, among the 341 monitored cities, the annual average ambient SO2 concentration exceeded the Class-II standard (60μg/m3) in 26 percent of the cities. Fifty-five percent of the cities had annual average PM10 (TSP) levels violating the Class-II standard (100μg/m3). Annual average NO2 concentrations of all monitored cities met the Class-II standard (50μg/m3). This suggests that particulate matter has become the air pollutant of primary concern in China.

2) Different air pollutants may have a synergetic effect on human health. For instance, the combined effect of SO2 and PM10 may be higher (or lower) than the sum of the two components when they occur in isolation. Moreover, a part of PM10 may be sulfate, which is converted SO2. In spite of a large body of studies, the contribution of each of these pollutants to health damage is difficult to disentangle. In our view, adding the health cost from, respectively, PM10 and SO2 may lead to double counting.

3) The trial calculation results showed that the health cost estimated for SO2 (based on the dose-response coefficients in the December 2002 Progress Report of Chinese Environmental Cost Model) represented only about one-tenth of the total health cost due to air pollution.

Exposure-Response Relationships : Review of Epidemiological Evidence

The effects of air pollution on human health include the chronic effects of long-term exposure and the acute effects of short-term exposure. In the past two decades, a large number of studies—especially short-term, time-series studies—have reported exposure-response relationships between air pollution exposure and human health. Longterm cohort studies provide the best method to evaluate the chronic effects of air pollution on human health, whereas time-series studies are appropriate for revealing the acute effects of short term fluctuations in pollution levels. Exposure response coefficients from cohort studies of premature mortality are typically several times higher than coefficients reported in time-series studies. We assumed that the short-term effects found in time-series studies are embedded in the long-term effects on mortality rates derived from cohort studies.

A large number of time-series studies of mortality have been published in the past 20 years, but only a few cohort studies have appeared. In China, there are some time-series studies and several cross-sectional mortality studies, conducted in cities such as Beijing (Chang et al. 2003; Chang, Wang, and Pan 2003; Dong et al. 1995; Dong et al. 1996; Gao et al. 1993; Xu et al. 1995; Xu et al. 1994), Shanghai (Kan and Chen 2003; Kan and Chen 2004), Shenyang (Wang, Lin, and Pan 2003; Xu et al. 1996a; Xu et al. 2000; Xu et al. 1996b), and Chongqing (Venners et al. 2003).

To derive exposure-response functions for air pollution and mortality applicable to the entire country, we undertook a systematic literature review and analyzed the available studies by means of meta-analysis and statistical trend analysis, and made a final selection according to the criteria mentioned above.

Cohort studies of long-term exposure

Cohort studies take advantage of spatial variation in air pollution concentrations to compare the incidence of disease and death in populations exposed over the long term to differing levels of air pollution. By following large populations
for many years, cohort studies estimate both numbers of deaths and, more importantly,
mean reduction in life span attributable to air pollution.

Evidence from cohort studies of populations in the United States indicates that long-term exposure to outdoor air pollution is associated with an increase in total mortality, cardiopulmonary mortality, and lung cancer mortality in adults. These cohort studies include the Harvard six-city study (Dockery et al. 1993), the ACS
cohort study (Pope et al. 1995), and the ACS extended study (Pope et al. 2002). The main background information and results are shown below

Ecological studies of air pollution and human health

There is no cohort study in China and only three cross-sectional studies that reflect the effects of long-term air pollution exposure on mortality. In China, Jing et al. (1999), Xu et al. (1996a, 1996b, 2000), and Wang et al. (2003) investigated
the chronic effects of air pollution on mortality in Shenyang and Benxi. They estimated relative risks by comparing mortality rates in the worst-polluted and the least-polluted areas of each city.

Links to the Main peer reviewed epidemiological studies

Air pollution 20 most cited papers map

Label: POPE-1995
Title: Particulate Air-Pollution As a Predictor of Mortality in a Prospective Study of US Adults
Journal: AMER J RESPIR CRIT CARE MED, vol. 151, p. 669-674, 1995

Label: POPE-2002
Title: Lung Cancer, Cardiopulmonary Mortality and Long Term Exposure to Fine Particulate Air Pollution
Journal: JAMA-J AM MED ASSN, vol. 287, p. 1132-1141, 2002

Jing, L., et al. 1999. “Association between air pollution and mortality in Benxi City.” Chinese Journal of Public Health 15(3): 211–12.

Wang, H., G. Lin, and X. Pan. 2003. “Association between total suspended particles and cardiovascular disease mortality in Shenyang.” Journal of Environment and Health 20(1): 13–15.

Xu, X., et al. 1994. “Air pollution and daily mortality in residential areas of Beijing, China.” Archives of Environmental Health 49(4): 216–22.

Xu, Z., et al. 1996a. “Effects of air pollution on mortality in Shenyang City.” Chinese Journal of Public Health 15(1): 61–64.

Xu, Z., et al. 1996b. “Relationship between air pollution and morbidity of chronic diseases in Shenyang City.” Chinese Journal of Public Health 15(2): 123–25.

Xu, Z., et al. 2000. “Air pollution and daily mortality in Shenyang, China.” Archives of Environmental Health 55(2): 115–20.

New England Journal of Medicine - An Association between Air Pollution and Mortality in Six U.S. Cities

In this prospective cohort study, we estimated the effects of air pollution on mortality, while controlling for individual risk factors. Survival analysis, including Cox proportional-hazards regression modeling, was conducted with data from a 14-to-16-year mortality follow-up of 8111 adults in six U.S. cities.

Bell, M., McDermott, A., Zeger, S., Samet, J., and Dominici, F. (2004). Ozone and Mortality in 95 U.S. cities from 1987 to 2000." Journal of American Medical Association, 292, 2372{2378. Colburn, A. and Johnson, P. (2003).

Air Pollution Concerns Not Changed by S-Plus Flaw." Science, 299, 665{666. Daniels, M., Dominici, F., Samet, J. M., and Zeger, S. L. (2000).

Estimating PM10-Mortality Dose-Response Curves and Threshold Levels: An Analysis of Daily Time-Series for the 20 Largest US Cities." American Journal of Epidemiology, 152, 397{412. Dockery, D., Pope, C. A., Xu, X., Spengler, J., Ware, J., Fay, M., Ferris, B., and Speizer, F. (1993).

An association between air pollution and mortality in six U.S. cities." New England Journal of Medicine, 329, 1753{1759. Dominici, F., Daniels, M., Zeger, S. L., and Samet, J. M. (2002a).

Air Pollution and Mortality: Estimating Regional and National Dose-Response Relationships." Journal of the American Statistical Association, 97, 100{111. Dominici, F., McDermott, A., Daniels, M., Zeger, S. L., and Samet, J. M. (2003).

A Special Report to the Health E ects Institute on the Revised Analyses of the NMMAPS II Data. The Health E ects Institute, Cambridge, MA. Dominici, F., McDermott, A., and Hastie, T. (2004).

Improved Semi-Parametric Time Series Models of Air Pollution and Mortality." Journal of American Statistical Association, to appear. Dominici, F., McDermott, A., Zeger, S. L., and Samet, J. M. (2002b).

0n the use of Generalized Additive Models in Time Series Studies of Air Pollution and Health." American Journal of Epidemiology, 156, 1{11. Dominici, F., Samet, J. M., and Zeger, S. L. (2000).

Combining Evidence on Air pollution and Daily Mortality from the Twenty Largest US cities: A Hierarchical Modeling Strategy (with discussion)." Royal Statistical Society, Series A, with discussion, 163, 263{302. Kaiser, J. (2002).

Software Glitch Threw O Mortality Estimates." Science, 1946{1947.
Kelsall, J., Samet, J. M., and Zeger, S. L. (1997). \Air Pollution, and Mortality in Philadelphia, 1974-1988." American Journal of Epidemiology, 146, 750{762. Kunzli, N., Medina, S., Kaiser, R., Quenel, P., Horak, F., and Studncka, M. (2001).

Assessment of Deaths Attributable to Air Pollution: Should We Use Risk Estimates based on Time Series or Cohort Studies?" American Journal of Epidemiology, 153, 1050{1055. Peng, R., Dominici, F., and Louis, T. (2005a).

Model Choice in Multi-Site Time Series Studies of Air Pollution and Mortality (with Discussion)." The Royal Statistical Society, Series C (to appear). Peng, R., Dominici, F., Pastor-Barriuso, R., Zeger, S., and Samet, J. (2005b).

Seasonal Analyses of Air Pollution and Mortality in 100 U.S. Cities." American Journal of Epidemiology, 161, 585{594. Peng, R. and Welty, L. (2004).

The NMMAPSdata package,." R News, 4, 2, 10{14.Pope, C. A., Thun, M., Namboodiri, M., Dockery, D., Evans, J., Speizer, F., and Heath, C. (1995).

Particulateair pollution as a predictor of mortality in a prospective study of U.S. adults." American JournalRespiratory Critical Care Medicine, 151, 669{674. Samet, J. M., Dominici, F., Curriero, F., Coursac, I., and Zeger, S. L. (2000).

Fine Particulate air pollution and Mortality in 20 U.S. Cities: 1987-1994." New England Journal of Medicine (with discussion), 343, 24, 1742{1757.

World Health Organization Outdoor Air Pollution Database

So now that it is clear that the correlation between air pollution effects is very, very solid. We can move to the World Health Organization Database of outdoor air pollution statistics of deaths and health impacts. Note- there is also a lot of peer reviewed information of the monitoring of air pollution levels which is tracked by the day and hour in most cities.

WHO outdoor air pollution website

WHO health impacts for outdoor air pollution

The WHO maintains that reducing the average outdoor air pollution in a city can lead to substantial long term reductions in mortality.

By reducing the annual mean outdoor concentration of PM10 from 70 to 20 µg/m3, the target level set out in the 2005 WHO Air Quality Guidelines, WHO estimates that 15% of long term mortality (i.e. deaths) from air pollution can be averted. Reaching these lower levels of air pollution will also reduce respiratory and cardiovascular diseases as well as increase life expectancy among local populations.

In addition, action to reduce urban air pollution will also cut emissions of greenhouse gases and other pollutants contributing to climate change. Climate change produces a number of adverse effects on health (other health impacts). This includes those from drought and extreme weather events (e.g. windstorms, floods), such as water-borne and food-borne diseases. It also increases the prevalence of vector-borne diseases like dengue or malaria

WHO database on outdoor air pollution health impacts

The burden of disease attributable to urban outdoor air pollution can be expressed as :

Number of deaths
Death rate
Number of DALYs (YLLs part of the DALYs only)
DALYs rate (YLLs part of the DALYs only)

Disability -Adusted Life Years (or DALYs) are a summary measure of population health that combine (i) the years of life lost (YLL) as a result of premature death and (ii) the years lived with a disease (YLD). In the case of outdoor air pollution, the DALYs consist of the YLL part only, as there is currently no adequate information on the morbidity part.

Death and DALY rates are calculated by dividing the number of deaths, resp. DALYs, by the total population (or indicated if a different population group is used, e.g. children under 5 years).

Evidence from epidemiological studies have shown that exposure to urban air pollution is linked, among others, to three important diseases taken into account in this estimate:

Respiratory infections in young children (estimated in under 5 years of age);
Cardiopulmonary disease in adults (estimated above 30 years); and
Lung cancer in adults (estimated above 30 years).

Burden of disease is calculated by first combining information on the increased (or relative) risk of a disease resulting from exposure, with information on how widespread the exposure is in the population (in this case, the annual mean concentration of particulate matter in the urban population of cities above 100'000 inhabitants).

This allows calculation of the 'population attributable fraction' (PAF), which is the fraction of disease seen in a given population that can be attributed to the exposure, in this case the annual mean concentration of particulate matter.

Applying this fraction to the total burden of disease (e.g. cardiopulmonary disease expressed as deaths or DALYs), gives the total number of deaths or DALYs that results from urban outdoor air pollution.

Calculate the population attributable fractions - Use the formula for estimating the population attributable fraction (PAF) for each health outcome:

PAF = [p(RR − 1)]/[p(RR − 1) + 1]

where: p = proportion exposed to the risk factor in the specified age group; RR = relative risk for outcome in a specified population group

Relative risk is in the charts above 1.17 for PM10.

The RR factors and standard deviations are listed in summary charts for all causes 1.17 for PM10.

There are some other studies and different estimates of concentrations or in assumptions of how much pollution is reduced to get the baseline of not excess deaths changes the numbers of deaths.

Outdoor Air Pollution Deaths for 2008 by Country
China      470649
India      168601
Russia      68827
USA         56618
Pakistan    45300
Ukraine     31765
Nigeria     25474
Indonesia   25315
Turkey      24797
Brazil      23723
Japan       23253
Iran        17947
Mexico      14734
Egypt       13992
UK          13604
Germany     11629
Philippines 11012
Italy       10370
Vietnam     10312
France       7535

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