Environmental Health
Refer to: Mahoney LE: Air pollution and respiratory mortality in Los Angeles (Environmental Health). West J Med 124:159-166, Feb 1976
Air Pollution and Respiratory Mortality in Los Angeles LOUIS E. MAHONEY, MD, Dr PH, San Bernardino
An epidemiologic study in Los Angeles showed a regular statistical association between respiratory mortality and the spatial distributions of ozone and particulate matter. There was an irregular association of respiratory mortality with maximum temperature. These findings are consistent with those of other studies relating respiratory morbidity to oxidant and particulate air pollution, and suggest that these pollutants may be health hazards.
AIR POLLUTION in Los Angeles has caused considerable political and technical concern for a generation. Despite 25 years of research, however, no consistent studies have appeared to describe the effects of the city's oxidant air pollution on human health. Mills",2 suggested a significant influence of oxidant air pollution on daily mortality from cardiac and respiratory causes; results in studies by a group from the California State Health Department3-5 do not confirm this finding. Sterling and others6-8 have reported that increases in hospital admissions for a number of diseases were related to daily concentrations of oxidants and other pollutants. Findings in a preliminary study of respiratory mortality in Los Angeles9 showed that death rates from respiratory disease were increased in downwind areas of the city. The increase was indeFrom the School of Public Health, University of California, Los Angeles, and the Los Angeles County Health Services Department. This work was supported by Public Health Services Training Grant GM-1141. Computing assistance was obtained from the Health Services Computing Faculty, UCLA, supported by Grant FR-3 from the National Institutes of Health. Reprint requests to: Louis E. Mahoney, MD, Dr PH, Director of Public Health, County of San Bernardino, 351 N. Mountain View Avenue, San Bernardino, CA 92415.
pendent of different age, sex and income characteristics of different "wind zones" within the city. These findings were consistent with an effect of air pollution or of some meteorologic factor associated with wind flow. Sources of air pollution in Los Angeles are predominantly diffuse. The troublesome primary pollutants of other areas-principally sulfur oxides and particulates-are less prominent in Los Angeles because of economic and climatic differences. Oxidant, however, accumulates within masses of air as they move across the city. This secondary pollutant could be responsible for the mortality increase associated with wind flow. In order to shed more light on respiratory disease in Los Angeles, it seemed reasonable to examine mortality for association with each of the "classical" air pollutants known to be associated with respiratory disease elsewhere, and for association with oxidant. The principal climatologic covariates of oxidant-maximum and minimum temperature-were examined at the same time. A spatial model was tested, rather than the temporal models studied by other investigations. THE WESTERN JOURNAL OF MEDICINE
159
AIR POLLUTION AND RESPIRATORY MORTALITY ABBREVIATIONS USED IN TEXT DMHA=daily maximum hourly averages 1DM=instantaneous daily maximum
Methods Statistical considerations mandated a study period closely related to a decennial census. The study was begun in 1968, when data from the 1969-1971 pericensal period were not yet available. Inconsistencies in tabulation of 1959-1960 and 1961 data prevented merger of these years. The 1961 data set was chosen therefore in order to use the more detailed geographical divisions of the 1960 census. Lack of funding has prevented repetition of the study with 1969-1971 data. Methods of investigation were essentially the same as those of the wind flow study.9 Charts of the spatial distribution of suspected pollutant or meteorologic variables were used to assign a representative level of exposure for each variable to all census tracts of the city. The populations of these tracts were then pooled by levels of each variable under consideration, and mortality rates were computed for each level, adjusted for different age, sex and income characteristics of the different groups. A chi-square statistic was used to test the hypothesis that there was no difference in mortality between levels of exposure. Pollutant data. The Los Angeles County Air Pollution Control District provided charts of isopleths of 90th percentile daily maximum values of ozone, sulfur dioxide and suspended particulates for the year 1961. These charts were enlarged onto standard census tract maps using a TABLE 1.-Selected Respiratory Deaths by Cause, Los Angeles White Study Population, 1961 Cause of Death
ICD* Code
241 470-475 480-483 490-493 500-502 510-517 518-521 525 526 527
Asthma .61
9 Upper respiratory infections Influenza .29 Pneumonia .597 Bronchitis .49 Other upper respiratory diseases 8 Pleurisy, empyema, pneumothorax, and lung abscess .14 Other nonoccupational interstitial pneumonias .48 Bronchiectasis .33 Other diseases of lung and pleura ... 198 All selected deaths ............. 1,046
*International
160
Deaths
Classification of Diseases, 7th Revision, 1957
FEBRUARY 1976 * 124 * 2
pantograph, with an estimated mechanical accuracy of half a mile. Six to nine pollutant stations were used to estimate pollution distributions; two stations 13 miles apart provide the only data for the San Fernando Valley, while up to eight stations generally about 5 miles apart provide data for the remainder of the city. This potential source of error is partly counterbalanced by the larger area and lower population density of census tracts in the San Fernando Valley, which tend to minimize the effect of malpositioning of boundaries between pollutant levels. Temperature data. Temperature data were obtained from routine publications of the Weather Bureau'0 in the form of charts of isotherms of January mean minimum temperature and July mean maximum temperatures for the years 19311952. These charts were reproduced photographically and projected on census tract maps by a camera-lucida arrangement, with an estimated error in position of a quarter mile. These charts represent 21 year means from 18 data collecting stations generally less than five miles apart. The precision of estimates is somewhat lower in mountainous areas than on the plain, but this is of slight effect because the mountainous areas are very sparsely populated. These data need not specifically refer to the year 1961, as the spatial distribution of maximum and minimum temperatures does not change radically from year to year. Data processing. The census tract maps thus obtained for pollutant and temperature variables were examined, and each tract was assigned the value shown by the immediately lower isopleth or isotherm. Intermediate values were not interpolated. Between isopleths representing 20 and 22.5 parts per 100 million (pphm) of ozone, for instance, all tracts would be assigned the value 20. These values were keypunched in sets for each variable and screened on the computer for duplicate or missing values, and a sample was then manually rechecked for accuracy. They were then copied onto online disk storage along with 1960 census data by tract to facilitate further processing. Census and death data utilized were identical to those used in the pilot study,9 except that all census tracts of the city were available for analysis. The white population of the city at the time of the 1960 census was again taken as the study population. Death certificates from the year 1961 were obtained on magnetic tape, and sorted for respiratory deaths due to causes coded 241, 470-
AIR POLLUTION AND RESPIRATORY MORTALITY TABLE 2.-Respiratory Mortality by Age and Sex, Los Angeles City White Residents, 1961 Female
Male
Rate/lOOM
Population
Rate/lOOM
... 98,226 0-4 5-14 ... 170,403 15-24 ... 113,813 25-34 ... 137,967
74.3 3.5 1.8 4.3
94,983 165,385 125,100 135,762
57.9 3.0 2.4 2.9
... ... ... ... ... ...
13.4 28.8 64.7 140.2 225.8 380.5
156,873 136,412 60,253 54,869 49,360 39,276
4.5 16.9 36.5 45.6 46.6 109.5
734.7
49,746
375.9
Population
Age
35-44 45-54 55-59 60-64 65-69 70-74 75+
149,653 128,408 54,115 44,951 37,636 28,120 29,265
TABLE 3.-Standardized Mortality Ratios (SMR) and Mortality Rates for Respiratory Diseases by Level of Income, Adjusted for Age and Sex, Los Angeles City Whites, 1961 Income Level*
Deaths Population Expected Actual
$8,430 + ..... 517,870
$7,350-8,429 $6,228-7,349 $5,153-6,227
$
0-5,152
482,414 471,134 362,862
Mortality SMR Rate/lOOM
202
145
72
36.4
198 248 230
151 224 244
76
38.7 45.8 54.0
90
106
168 226,296 168 282 x2= 108.0, 4df, P
Refer to: Mahoney LE: Air pollution and respiratory mortality in Los Angeles (Environmental Health). West J Med 124:159-166, Feb 1976
Air Pollution and Respiratory Mortality in Los Angeles LOUIS E. MAHONEY, MD, Dr PH, San Bernardino
An epidemiologic study in Los Angeles showed a regular statistical association between respiratory mortality and the spatial distributions of ozone and particulate matter. There was an irregular association of respiratory mortality with maximum temperature. These findings are consistent with those of other studies relating respiratory morbidity to oxidant and particulate air pollution, and suggest that these pollutants may be health hazards.
AIR POLLUTION in Los Angeles has caused considerable political and technical concern for a generation. Despite 25 years of research, however, no consistent studies have appeared to describe the effects of the city's oxidant air pollution on human health. Mills",2 suggested a significant influence of oxidant air pollution on daily mortality from cardiac and respiratory causes; results in studies by a group from the California State Health Department3-5 do not confirm this finding. Sterling and others6-8 have reported that increases in hospital admissions for a number of diseases were related to daily concentrations of oxidants and other pollutants. Findings in a preliminary study of respiratory mortality in Los Angeles9 showed that death rates from respiratory disease were increased in downwind areas of the city. The increase was indeFrom the School of Public Health, University of California, Los Angeles, and the Los Angeles County Health Services Department. This work was supported by Public Health Services Training Grant GM-1141. Computing assistance was obtained from the Health Services Computing Faculty, UCLA, supported by Grant FR-3 from the National Institutes of Health. Reprint requests to: Louis E. Mahoney, MD, Dr PH, Director of Public Health, County of San Bernardino, 351 N. Mountain View Avenue, San Bernardino, CA 92415.
pendent of different age, sex and income characteristics of different "wind zones" within the city. These findings were consistent with an effect of air pollution or of some meteorologic factor associated with wind flow. Sources of air pollution in Los Angeles are predominantly diffuse. The troublesome primary pollutants of other areas-principally sulfur oxides and particulates-are less prominent in Los Angeles because of economic and climatic differences. Oxidant, however, accumulates within masses of air as they move across the city. This secondary pollutant could be responsible for the mortality increase associated with wind flow. In order to shed more light on respiratory disease in Los Angeles, it seemed reasonable to examine mortality for association with each of the "classical" air pollutants known to be associated with respiratory disease elsewhere, and for association with oxidant. The principal climatologic covariates of oxidant-maximum and minimum temperature-were examined at the same time. A spatial model was tested, rather than the temporal models studied by other investigations. THE WESTERN JOURNAL OF MEDICINE
159
AIR POLLUTION AND RESPIRATORY MORTALITY ABBREVIATIONS USED IN TEXT DMHA=daily maximum hourly averages 1DM=instantaneous daily maximum
Methods Statistical considerations mandated a study period closely related to a decennial census. The study was begun in 1968, when data from the 1969-1971 pericensal period were not yet available. Inconsistencies in tabulation of 1959-1960 and 1961 data prevented merger of these years. The 1961 data set was chosen therefore in order to use the more detailed geographical divisions of the 1960 census. Lack of funding has prevented repetition of the study with 1969-1971 data. Methods of investigation were essentially the same as those of the wind flow study.9 Charts of the spatial distribution of suspected pollutant or meteorologic variables were used to assign a representative level of exposure for each variable to all census tracts of the city. The populations of these tracts were then pooled by levels of each variable under consideration, and mortality rates were computed for each level, adjusted for different age, sex and income characteristics of the different groups. A chi-square statistic was used to test the hypothesis that there was no difference in mortality between levels of exposure. Pollutant data. The Los Angeles County Air Pollution Control District provided charts of isopleths of 90th percentile daily maximum values of ozone, sulfur dioxide and suspended particulates for the year 1961. These charts were enlarged onto standard census tract maps using a TABLE 1.-Selected Respiratory Deaths by Cause, Los Angeles White Study Population, 1961 Cause of Death
ICD* Code
241 470-475 480-483 490-493 500-502 510-517 518-521 525 526 527
Asthma .61
9 Upper respiratory infections Influenza .29 Pneumonia .597 Bronchitis .49 Other upper respiratory diseases 8 Pleurisy, empyema, pneumothorax, and lung abscess .14 Other nonoccupational interstitial pneumonias .48 Bronchiectasis .33 Other diseases of lung and pleura ... 198 All selected deaths ............. 1,046
*International
160
Deaths
Classification of Diseases, 7th Revision, 1957
FEBRUARY 1976 * 124 * 2
pantograph, with an estimated mechanical accuracy of half a mile. Six to nine pollutant stations were used to estimate pollution distributions; two stations 13 miles apart provide the only data for the San Fernando Valley, while up to eight stations generally about 5 miles apart provide data for the remainder of the city. This potential source of error is partly counterbalanced by the larger area and lower population density of census tracts in the San Fernando Valley, which tend to minimize the effect of malpositioning of boundaries between pollutant levels. Temperature data. Temperature data were obtained from routine publications of the Weather Bureau'0 in the form of charts of isotherms of January mean minimum temperature and July mean maximum temperatures for the years 19311952. These charts were reproduced photographically and projected on census tract maps by a camera-lucida arrangement, with an estimated error in position of a quarter mile. These charts represent 21 year means from 18 data collecting stations generally less than five miles apart. The precision of estimates is somewhat lower in mountainous areas than on the plain, but this is of slight effect because the mountainous areas are very sparsely populated. These data need not specifically refer to the year 1961, as the spatial distribution of maximum and minimum temperatures does not change radically from year to year. Data processing. The census tract maps thus obtained for pollutant and temperature variables were examined, and each tract was assigned the value shown by the immediately lower isopleth or isotherm. Intermediate values were not interpolated. Between isopleths representing 20 and 22.5 parts per 100 million (pphm) of ozone, for instance, all tracts would be assigned the value 20. These values were keypunched in sets for each variable and screened on the computer for duplicate or missing values, and a sample was then manually rechecked for accuracy. They were then copied onto online disk storage along with 1960 census data by tract to facilitate further processing. Census and death data utilized were identical to those used in the pilot study,9 except that all census tracts of the city were available for analysis. The white population of the city at the time of the 1960 census was again taken as the study population. Death certificates from the year 1961 were obtained on magnetic tape, and sorted for respiratory deaths due to causes coded 241, 470-
AIR POLLUTION AND RESPIRATORY MORTALITY TABLE 2.-Respiratory Mortality by Age and Sex, Los Angeles City White Residents, 1961 Female
Male
Rate/lOOM
Population
Rate/lOOM
... 98,226 0-4 5-14 ... 170,403 15-24 ... 113,813 25-34 ... 137,967
74.3 3.5 1.8 4.3
94,983 165,385 125,100 135,762
57.9 3.0 2.4 2.9
... ... ... ... ... ...
13.4 28.8 64.7 140.2 225.8 380.5
156,873 136,412 60,253 54,869 49,360 39,276
4.5 16.9 36.5 45.6 46.6 109.5
734.7
49,746
375.9
Population
Age
35-44 45-54 55-59 60-64 65-69 70-74 75+
149,653 128,408 54,115 44,951 37,636 28,120 29,265
TABLE 3.-Standardized Mortality Ratios (SMR) and Mortality Rates for Respiratory Diseases by Level of Income, Adjusted for Age and Sex, Los Angeles City Whites, 1961 Income Level*
Deaths Population Expected Actual
$8,430 + ..... 517,870
$7,350-8,429 $6,228-7,349 $5,153-6,227
$
0-5,152
482,414 471,134 362,862
Mortality SMR Rate/lOOM
202
145
72
36.4
198 248 230
151 224 244
76
38.7 45.8 54.0
90
106
168 226,296 168 282 x2= 108.0, 4df, P
