Environmental chromium dust and lung cancer mortality

ENVIRONMENTAL

RESEARCH

23, 469-476 (1980)

Environmental

Chromium Dust and Lung Cancer Mortality

GOSTAAXELSSON Department

ANDRAGNARRYLANDER

of Environmental Hygiene, 400 33 Gothenburg,

University Sweden

of Gothenburg.

Received June 9, 1980 A register study was performed in a Swedish county to investigate lung cancer mortality in a population exposed to air pollutants from ferro-alloy industries. During 1961- 1975, 810 lung cancer deaths were analyzed. A strong relation between population density and lung cancer mortality was found. When this factor was controlled no differences in mortality rates were found between the communities with ferro-alloy industry and the remainder of the county. A general increase in lung cancer mortality most marked for males was found over this time period.

INTRODUCTION

The study of the geographical distribution of diseases is a useful epidemiological tool for the formulation of hypotheses concerning the influence of environmental factors. Results from geographical distribution studies of lung cancer in the United States have demonstrated an accumulation of cases in certain industrial areas (Blot and Fraumeni, 1976), and, in particular, near areas with a heavy concentration of ship-building industries or oil refineries (Rothschild et al., 1979; Blot et al., 1977). Metals have been suggested as a risk factor for the development of malignant pulmonary disease. In a rural county in the west of Sweden (Alvsborg) are situated two ferro-alloy industries, one plant started in 1913 in Trollhattan and one started in 1912 in Vanersborg. The plants are located at a distance of about 10 km from one another. The dusts emitted from the industries contain chromium and manganese and between 1976 and 1979 the emissions were measured in an air pollution control program. The average monthly values of chromium dust in the air were determined at five measuring stations in the communities of Trollhattan and Vanersborg. The concentration of chromium in the air in the most polluted areas varied between 100 and 400 ng/m3, which is SO- 100 times higher than the concentration in a rural area without industrial emissions. Chromates have been related to the development of lung cancer among industrial populations (Enterline, 1974), although exposure to trivalent chromium in ferrochromium industries does not seem to increase the lung cancer risk (Axelsson et al., 1980). However, a synergistic effect of other air pollutants in the surroundings of the plants cannot be excluded. It was therefore considered of interest to study the lung cancer mortality rate among the population around the ferro-alloy plants. 469 0013-9351/80/060469-08$02.00/O Copyright @ 1!330 by Academic Press, Inc. All rights of reproduction in any form reserved

470

AXELSSON

AND

RYLANDER

A register study was undertaken in the county where the industries were located and mortality from lung cancer was analyzed for the years 1961-1975 for the whole county and was compared to the mortality rates in different regions of the county, and Sweden as a whole. MATERIAL

AND METHODS

The investigation was performed using data from the National Central Bureau of Statistics on Causes of Death. The data were collected for the county of Alvsborg for the time periods 1961- 1969 and 1970- 1975. The diagnoses included in the study were ICD 162- 164 (7th revision) during 1961- 1968 and ICD 162 and 163 (8th revision), 1969- 1975. A manual search of the register for all cases in the county was done for the period 1961- 1969. For the time period 1970- 1975, the information for ICD 162 was received from computerized data files, while deaths from ICD 163 were obtained from death certificates. The birth numbers (year/month/day/registration number), dates of death, and home parishes were obtained for the manually obtained data. The search of the computerized data register gave only the age-stratified number of cases in each of the 18 communities in the county. From this information the cases were traced in local parish death registers. Several changes in the county’s division of communities had been made during the time period which was covered in the study. Data were adjusted to relate to the situation as of January 1977. The age structure and size of the population were estimated from the National Censuses of 1960, 1965, and 1970. The age specific mortality in five-year classes was calculated for both sexes in each community during the periods 1961- 1964, 1965-1969, and 1970-1975. As the age distribution of the population varied between different communities within the county, the mortality rate was ageadjusted and related to a standard population of the whole county. The mean lung cancer mortality rate for the population in each community was calculated for the whole period. For the three periods the material on the county level was divided into three groups according to the population size of the parishes in 1965. Three parishes had 20,000 or more inhabitants. Seven had 5000- 19,999 inhabitants, and 205 had less than 5000 inhabitants. The age-adjusted lung cancer mortality rate in each group of parishes was calculated for both sexes during these periods. Trollhattan community consists of one parish with approximately 40,000 inhabitants and seven parishes, mainly rural, each with less than 5000 inhabitants. Vanersborg community also has seven parishes with less than 5000, and one parish with 19,000 inhabitants. The mortality rates in the two communities were compared to the remaining parishes in the county of the same population size. The lung cancer mortality rate in the county was also related to the figures for Sweden as a whole. The rate difference between 1961- 1964 and 1970- 1975 was calculated for Sweden, Alvsborg county, Trollhattan, and Vanersborg. The 95% confidence limits for the rate difference and a x2 test for differences in mortality rates between communities were calculated according to the method described by Miettinen (1976).

CHROMIUM

AGE-ADJUSTED

AMONG MALES,

DUST

AND

LUNG

471

CANCER

TABLE 1 LUNG CANCER MORTALITY RATES (DEATHS PER MILLION INHABITANTS) 1961- 1975, IN ~~LVSBORGCOUNTY AND IN THE Two COMMUNITIESEXPOSED

TO EMISSIONS FROM FERRO-ALLOY INDUSTRIES Period 1961-1975 Sweden Alvsborg county Trollhittan Vanersborg n Number

of lung cancer

1961-1964

19655 1969

1970-

1975

326

243

305

400

194(580)n 253 (73) 161 (40)

136(102) 171 (12) 177 (11)

183(180) 263 (24) 157 (13)

243(298) 299 (37) 154 (16)

deaths

in parentheses.

RESULTS

The lung cancer mortality rate in the 18 communities in the county varied between 115 and 254 per million among males and 40 and 132 among females. The complete data are reported in the Appendix. Table 1 reports the age-adjusted lung cancer mortality rate for males as deaths per million inhabitants and the number of cases during the three different time periods in the county and communities where the ferro-alloy industries are located. The mortality rate in the county was 194 per million during the whole time period studied which was significantly lower than the rate for Sweden as a whole (P < 0.001). The rate in Trollhattan was higher than for the county (Z’ < 0.05) but still lower than the rate for Sweden. The mortality in Vanersborg was low. Over the time period studied the mortality rate in the county increased from 136 during 1961-1964 to 243 during 1970-1975. This increase is statistically significant (x2 = 21.8, P < 0.001) but is significantly less (P < 0.05) than the increase for Sweden as a whole during the same period (243 to 400). The increase in Trollhattan paralleled the increase in the county, whereas no increase over time was found in Vanersborg. TABLE

2

AGE-ADJUSTED LUNCCANCERMORTALITY RATES(DEATHS PER MILLION INHABITANTS)AMONG FEMALES, 1961-1975, IN ALVSBORG COUNTY AND IN THE Two COMMUNITIES EXPOSEDTO EMISSIONS FROM FERRO-ALLOY INDUSTRIES Period 1961Sweden Alvsborg county Trollhattan Vanersborg o Number

of lung cancer

1975

1961-1964

1965-

1969

88

67

75

78(230)” 74 (20) 80 (20)

69(52) 62 (4) 65 (4)

75(73) 57 (5)

deaths

in parentheses.

96 (8)

1970-

1975

112 86( 105) 95 (11) 76 (8)

472

AXELSSON

AND RYLANDER

OGSSO <50005000-19999

3 20000

400 5 a3

300-

E cn

zoo-

5

loo-

x 1961-1964

865-1969

1970-1975

1961-1975

FIG. 1. Age-adjusted lung cancer mortality rates for males in parishes with different population sizes in Alvsborg county during three time periods. The number of cases in each class is shown on the columns.

Table 2 presents the lung cancer mortality data for females. The mortality rate in the county was slightly lower than the rate in Sweden but the difference was not statistically significant. The rate in the two exposed communities was close to the rate for the county. Over the time period studied the mortality rate in the county increased from 69 to 86 per million inhabitants. This increase was not statistically significant, nor was the increase found in Trollhattan. The increase in female lung cancer mortality in Sweden over the same period was from 67 to 112 (P < 0.001). Figure 1 shows the age-adjusted lung cancer mortality rates in parishes according to population size in iilvsborg county during the three time periods 1961-1964, 1965-1969, and 1970-1975. Over the whole time period studied the lung cancer mortality was related to the population size. If the different time periods were compared an increase in the mortality rate was seen in parishes with less than 5000 and in those with more than 20,000 inhabitants. Figure 2 shows the corresponding data for females. The relation between population size and lung cancer mortality was less clear-only parishes with less than 5000 inhabitants showed a slightly lower rate. Over the time period studied this was also found for 1961- 1964 and 1965- 1969. During 1970-1975 no relation could be found between population size and female lung cancer mortality. Table 3 shows the lung cancer mortality rates in Trollhattan and Vanersborg compared to those of the other parishes with the same population size in the

0GS-D. <50005000-19999

z

c-l

1961-1964

1965-1969

220000

19703975

1961-1975

2. Age-adjusted lung cancer mortality rates for females in parishes with different population sizes in Alvsborg county during three time periods. The number of cases in each class is shown on the columns. FIG.

CHROMIUM

473

DUST AND LUNG CANCER TABLE

3

LUNG CANCER MORTALITY RATES, 1961- 1975, IN TROLLHATTAN AND VANERSBORG COMPARED TO THE OTHER PARISHES IN THE COUNTY WITH THE SAME POPULATION SIZE

Population 4,000 5,000- 19.999 ~20,000

Sex M F M F M F

Trollhattan 141(10)0 34 (2) -1’ 288(63) 8318)

a Number of lung cancer deaths in parentheses. b-’ Indicates that no parish with corresponding population

Vanersborg

Other parishes

9W)

144(229) 69 (99) 247( 103) 95 (43) 278( 135) 93 (48)

76(8) 227(31) 80( 12) -

size was present.

county. The mortality rate in Trollhattan was very close to the other parishes with the same population size for both sexes. In Vanersborg the mortality rate was slightly lower than those of the other parishes in Alvsborg county, although the difference was not statistically significant. Figure 3 illustrates the age-specific mortality rate from lung cancer for males in the two parishes in which the ferro-alloy industries were located and in the remaining parishes in the county with the same population size. The age-specific mortality rate of Trollhattan did not exceed that for the corresponding parishes in any age group. In Vanersborg, the mortality rate was higher (547 per million) than that in other parishes of the same size (179 per million) in the age interval 55-59 years. DISCUSSION

The results of the study are influenced by the completeness and accuracy of the death register data and the number of persons who moved after a possible exposure causing lung cancer took place, but before the cancer developed. In Sweden, a death certificate is issued for all deaths. These are collected at the National Central Bureau of Statistics, where the underlying cause of death is codified. A certain number of persons with diagnosed lung cancer who were alive at the time of the study were not included in the registers used. In order to include such persons it would have been necessary to use the Swedish Cancer Register. This register has technical limitations, however, in that complete information on the

FIG. 3. Age-specific mortality rates from lung cancer for males in Trollhattan the other parishes in the county with the same population size.

and Vanersborg and

474

AXELSSON

AND

RYLANDER

community level was available only for 1971- 1973. It was thus preferable to use the data from official death certificates. Taking into consideration that a patient with lung cancer has a relatively short survival time, the errors caused by the omission of living lung cancer cases should be small. Also, there is no reason to believe that the number of living lung cancer cases is unevenly distributed in the county or related to the presence of the ferro-alloy industry. The proportion of the population which moved out of the county varied between 4 and 6% per year and the proportion from the communities where the ferro-alloy industries were located did not exceed this figure. Population migration could thus not influence the comparison in lung cancer mortality between the communities with fen-o-alloy industry and the rest of the county. The results demonstrate that the mortality rate from respiratory tumors among males in the county increased during the time period studied. The same tendency was found for females. This development had been seen earlier for Sweden as a whole (Edling, 1978) and for other countries (Waterhouse ef al., 1976). During the last period of the investigation, the female death rate showed a greater tendency to increase, which also corresponds to observations in other countries (Devesa and Silverman, 1978; Adelstein, 1978). A relationship between the population size of the parishes and lung cancer death rate was demonstrated for both sexes. A similar finding was reported in a study on the geographical variation of respiratory cancer in the United States (Blot and Fraumeni, 1979). In that study, a positive gradient was found with urbanization, where rates in highly urban areas exceeded those in rural areas by 50% or more. An evaluation of a possible increase in lung cancer mortality in communities with the ferro-alloy industry must thus be made between parishes with the same population size. This analysis could not demonstrate a higher lung cancer mortality among the populations exposed to exhaust from the ferro-alloy industry. If a particular exposure causing lung cancer was present in a given community it could, apart from causing a general increase in lung cancer mortality, result in the development of lung cancer at earlier ages. No such tendency was demonstrated when the age-specific lung cancer mortality rates in the two parishes with ferroalloy industries were compared to the rates of other parishes of the same size in the county. The general increase in lung cancer mortality rate over time has often been interpreted as being caused by an augmented consumption of cigarettes since the time of the second world war. Additional factors could be an increase in industrialization with a correspondingly increased occupational air pollution exposure and an increase in the amount of urban air pollution. The reason for the higher lung cancer rate in urban areas may, apart from smoking habits, also be related to exposure to occupational or urban air pollution. Areas with large population size are generally more industrialized than small towns and rural areas. For instance, in Trollhattan, mechanical, chemical, and machinery industries engage about 50% of the working population, as compared to 20% in Vanersborg. Considerable use of asbestos has taken place in heavy industry in Trollhattan. In a previous investigation, an accumulation of employees with

CHROMIUM

DUST

AND

APPENDIX AGE-ADJUSTED

LUNG

1961-

County

CANCER

COMMUNITIES

475

CANCER

TABLE 1 RATES (DEATHS

MORTALITY

1975, IN ALL

LUNG

WITHIN

PER MILLION)

ALVSBORG

Community

1961-1964

1965-

1969

1970-

Dals-Ed Fargelanda Ale Lerum Vargarda Tranemo Bengtsfors Mellerud Lilla Edet Mark Svenljunga Herrljunga Vanersborg Trollhattan Alingsas Boras Ulricehamn Amal

147 108 123 145 173 118 100 71

168

(3)

128 146 291 349 172 282 299 186 292 204 231 182 154 299 141 336 90 269

56 82 89 0 177 171 82 172 249 93

total

n Number

(2)” (2) (3) (4) (3) (3) (3) (2) (1) (5) (2) (0) (11) (12) (4) (29) (13) (3)

136(102) of lung cancer

deaths

83 (2) 293 172 40 211 123 179 182 171 168 171 157 263 185 220 63 252

183(180)

FEMALES, Community Dals-Ed Fargelanda Ale Lerum Vargtlrda Tranemo Bengtsfors Mellerud Lilla Edet Mark Svenljunga Herrljunga Vatrersborg Trollhattan Alingsas Boras Ulricehamn Amal County

total

LUNG

1961-

MALES,

1975 (2) (4) (13) (16) (5) (10) (15) (8) (10) (21) (8) (6) (16) (37) (11) (96) (7) (13)

243(298)

1961-

1975

146 (7) 115 (8) 247 (27) 236 (26) 128 (9) 215 (19) 187 (23) 153 (16) 192 (16) 160 (39) 172 (15) 130 (11) 161 (40) 253 (73) 140 (26) 254(175) 123 (24) 216 (26) 194(580)

in parentheses.

APPENDIX AGE-ADJUSTED

(11) (6) (1) (6) (5) (6) (5) (13) (5) (5) (13) (24) (11) (50) (4) (10)

AMONG

COUNTY

TABLE

2

CANCER MORTALITY RATES (DEATHS PER MILLION) AMONG 1975, IN ALL COMMUNITIES WITHIN ~~LVSBORG COUNTY

1961-1964 148 (2)” 115 (2) 104 (3)

78 (2)

196553 42 124 44 43 0 79 32 37 63 118 85 96 57

1969 (1) (1) (4) (2) (1) (0) (3) (1) (1) (5) (3) (2) (8) (5)

1970-

1975

44 57 86 153

(1) (1) (4) (7)

81 (2) 32 (1)

0 (0) 101 (2) 33 (1) 0 (0) 0 (0) 65 (4) 0 (0) 143 (3) 65 (4) 62 (4) 75 (4) 71(13) 166 (8) 0 (0)

92(23) 31 (2) 128 (5)

95 (11) 71 (6) 88 (28) 77 (6) 81 (4)

69(52)

75(73)

86( 105)

88 (6)

71 87 154

(3) (4) (5)

58 (6) 89 165

(3) (5)

76 (8)

1961-1975 75 67 103 97 47 40 64 45 74 62 75 132 80 74 78 85 85 70

(4) (4) (11) (11) (3) (3) (7) (5) (6) (15) (6) (10) (20) (20) (16) (64) (16) (9)

78(230)

476

AXELSSON

AND

RYLANDER

mesothelioma was demonstrated in one of the industries (Englund, personal communication). As pleural mesotheliomas are included in the present material, some of these cases are reported in the material for Trollhattan. It is thus likely that occupational asbestos exposure contributed to the lung cancer mortality rate in Trollhattan. No studies on individual cases and their occupational exposure could be performed in the study. In conclusion the results from this study could not demonstrate an increase in lung cancer mortality among a population exposed to exhaust from ferrochromium industries. An increase in lung cancer mortality rate over time was observed as well as a relation between population size and mortality rate. ACKNOWLEDGMENT Funds from the Vanersborg-Trollhattan Air Preservation Society, the County Medical Officer Organisation and the Swedish Cancer Society, are gratefully acknowledged.

REFERENCES Adelstein, H. M. (1978). Current Vital Statistics: Methods and Interpretations. &it. Med. J. 2, 983-987. Axelsson, G., Rylander, R., and Schmidt, A. (1980). Mortality and tumor incidence among ferrochromium workers. &it. J. Ind. Med. 37, 121- 127. Blot, W. J., and Fraumeni, J. F. (1976). Geographic patterns of lung cancer: Industrial correlations. Amer. .I. Epidemiol. 103, 5399550. Blot, W. J., and Fraumeni, J. F. (1979). Studies of respiratory cancer in high risk communities. J. Occup. Med. 21, 276-278. Blot, W. J., et al. (1977). Cancer mortality in the United States. Counties with petroleum industries. Science 198, 51-53. Devesa, S., and Silverman, D. (1978). Cancer incidence and mortality trends in the United States 1935-1974. J. Nat. Cancer Inst. 60, 545-571. Edling, C. (1978). Lung cancer mortality in Sweden 1964-1976. Liikartidningen 75, 3659-3661. [in Swedish]. Englund, A. Mesothelioma in an industry in Trollhattan. Personal communication. Enterline, P. E. (1974). Respiratory cancer among chromate workers. J. Occup. Med. 16, 523-526. Miettinen, 0. S. (1976). Estimability and estimation in case-referent studies. Amer. J. Epidemiof. 103, 226-235. Rothschild, H., Voors, A. W., Weed, S., Vial, L., Welsh, R. A., and Johnson, W. D. (1979). Trends in respiratory system cancer mortality in Louisiana: Geographic distributions in 1950-1969 and 1967-1976 compared. Amer. J. Pub. Health 69, 380-381. Waterhouse, J., Muir, C., Correa, P., and Powell, J. (1976). “Cancer Incidence in Five Continents,” Vol. III. IARC Scientific Publications No. 15. IARC, Lyon.