American Journal of Industrial Medicine 17:217-223 (1990)
Risk for Cancer of the Urinary Bladder Among Hairdressers in the Nordic Countries Torsten Skov, MD,Aage Andersen, MD, Hans Malker, PhD, Eero Pukkala, PhD, Jan Weiner, MS, and Elsebeth Lynge, MD
Several studies have indicated an increased risk for cancer of the urinary bladder among hairdressers. In a Danish linkage between census data and cancer register data both male and female hairdressers have an elevated risk for bladder cancer. The risk for lung cancer is close to unity, indicating that occupational factors rather than smoking, may be responsible lor the increased risk for bladder cancer among hairdressers. To evaluate this hypothesis we conducted a collaborative analysis of data from similar linkages in Finland, Norway, and Sweden. The combination of high risk for bladder cancer and low or no risk for lung cancer was not found in the other Nordic countries; however, statistically significant increased risks for both bladder and lung cancer were found among male hairdressers in both Norway and Sweden. The relative risks for bladder cancer were of the same magnitude as the relative risks for lung cancer. Key words: occupational cancer register, hair dyes, bladder cancer risk, occupational exposure
INTRODUCTION
Several hair dye ingredients are carcinogenic to animals [IARC, 1982; Flamm, 19851. The impact of the widespread non-occupational use of hair dye preparations has been extensively studied with special attention to cancer of the breast and, to a lesser extent, cancer of the bladder [Shafer and Shafer, 1976; Kinlen et al., 1977; Hennekens et al., 1979; Shore et al., 1979; Nasca et al., 1980; Wynder and Goodman, 1983; Green et al., 1987; Jain et al., 1977; Neutel et al., 1978; Hartge et al., 19821. Taken together these studies do not show any excess risk for cancer from non-occupational use of hair dyes. Several studies have shown elevated risk for bladder cancer among hairdressers, barbers, or beauticians [Wynder et al., 1963; Dunham et al., 1968; Anthony and Thomas, 1970; Howe et al., 1980; Silverman et al., 1983; Malker and Weiner, 1984; Dubrow and Wegman, 1984; Gubkran et al., 1985; Baxter and McDowall, 1986; Malker et al., 19871, but other studies have been
Danish Cancer Society, Danish Cancer Registry, Copenhagen, Denmark (T.S., E.L.). Norwegian Cancer Registry, Oslo, Norway (A.A.). National Board of Occupational Safety and Health, Solna, Sweden (H.M., J.W.). Finnish Cancer Registry, Helsinki, Finland (E.P.). Address reprint requests to Dr. T. Skov, Danish Cancer Society, Danish Cancer Registry, Rosenvaengets Hovedvej 35, Box 839, DK-2100 Copenhagen, Denmark. Accepted for publication September 13, 1989.
0 1990 Wiley-Liss, Inc.
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TABLE I. Design of the Nordic Occupational Cancer Studies
Country Census
Population studied
Norway
1960 15-69 years, economically active at census Sweden 1960 All ages, economically active at census Finland 1970 25-64 years at some time during follow-up, economically active at census Denmark 1970 20-64 years, economically active at census
Birth cohorts covered
Follow-~p period
Reference population
1891-1945
1961-84
All economically active
No restriction
1961-79
1906-1955”
1971-80
Total population in same region All economically active
1906-1950
1970-80
All economically active
“Birth cohorts 1906-1915 and 1946-1955 only partially covered, see “Materials and Methods.”
negative [Cole et al., 1972; Vineis and Magnani, 19851. Data from the Danish occupational cancer register-a linkage between census information and cancer register information-show that both male and female hairdressers experience an increased risk for bladder cancer and a risk for lung cancer close to unity [Lynge and Thygesen, 19881. The lack of an excess in the lung cancer risk indicates that factors other than smoking may be responsible for the excess risk for bladder cancer among Danish hairdressers. Linkage of census data with data from the national cancer registers has been undertaken in Finland, Sweden, Norway, and Denmark. The existence of these linked data offered an exellent opportunity to examine whether the pattern of cancer risk found among Danish hairdressers could also be found in the other Nordic countries. MATERIALS AND METHODS In four of the Nordic countries, Denmark, Finland, Norway, and Sweden, cross-sectionally registered census populations have been followed up for cancer incidence by individual record linkage. The census populations and follow-up periods of the study populations in the four countries are shown in Table I. Industry and occupation refer to the status at the time of the census [Pukkala et al., 1983; Malker, 1988; Lynge and Thygesen, 1988; Andersen et al., 19891. Hairdressers were identified by combining codes for occupation and industry (see Table 11). In all four countries all cancer cases during the follow-up period were coded according to ICD-7 [World Health Organization, 19571. Lung cancer includes only primary lung cancer (ICD-7 162.0,1), and bladder cancer includes invasive carcinoma (ICD-7 181.O) and papilloma, whether benign or malignant. The completeness of reporting of papillomas may vary among countries [Jensen et al., 1988aI. In Denmark the study population was restricted to persons aged 20-64 years at the 1970 census, in Norway to persons aged 15-69 years at the 1960 census, and in Finland to persons aged 25-69 years at any time during the follow-up period. In these countries the expected number of bladder cancer and lung cancer cases was calculated by multiplying the person-years at risk for each of the 5-year birth cohorts of male and female hairdressers with the sex-specific incidence rate for the equivalent 5-year birth
Occupational Risk for Cancer in Hairdressers
219
TABLE 11. Number of Hairdressers in the Nordic Studies ~~
Countrv
Industry code
Occupation code and descriution
No. of males
No. of females
941 hairdressers and beauticians 941 hairdressers and beauticians 840 hairdressers and barbers 395 hairdressers and barbers 01 1-040 self-employed
2, I49 6,522 428 1,177 3,697
4,356 16,942 9,138 4,160 5,337
13,973
39,933
~~
Norway Sweden Finland Denmark Denmark Total
All All All All 86 1 hairdresser
cohort of all persons who were economically active at the time of the census. In Sweden the study population was not age restricted. The expected number of bladder and lung cancer cases was calculated by multiplying the number of male and female hairdressers in a given region of Sweden in each 5-year birth cohort at the time of the census, with the sex-specific estimated disease probability for the equivalent 5-year birth cohort of all persons in the region. National figures were obtained by aggregating both observed and expected numbers across the 27 Swedish regions (24 counties and 3 largest cities). The observed number of cases divided by the expected number was used as an index of the relative risk (RR) in all four countries. Confidence intervals (CIS), 95%, were calculated under the assumption that the observed numbers of cancer cases followed a Poisson distribution [Bailar and Ederer, 19641. RESULTS The total number of hairdressers in the study series was 54,000 (Table 11). In Finland, hairdressing is clearly a woman’s job with 96% of hairdressers being female; in the other Nordic countries, at least two-thirds of the hairdressers were women. Male hairdressers in Norway and Sweden experienced a significantly increased relative risk for both bladder and lung cancer (Table 111). Among Danish male hairdressers the risk for bladder cancer was significantly increased, whereas the risk for lung cancer was 1.1. Finnish male hairdressers were so few that they had only three cases of lung cancer and no cases of bladder cancer. Table IV shows that the risk for bladder and lung cancer among female Norwegian hairdressers resembled that of their male counterparts, namely RRs for both cancers around 1.5. Swedish female hairdressers experienced a significantly increased risk for lung cancer and a decreased risk for bladder cancer. The numbers of cancer cases among Finnish female hairdressers were small, but the risks bear resemblance to those in Denmark, with increased risk for bladder cancer and decreased or unity risk for lung cancer. DISCUSSION
The combination observed among Danish hairdressers of low or unity risk for lung cancer and increased risk for bladder cancer was not found in the other Nordic countries except for female hairdressers in Finland where the numbers were small. The incidence of bladder cancer varies greatly among the Nordic countries; among men, it ranges from an age-standardized rate of 22.9 per 100,000 in Denmark
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Skov et al.
TABLE 111. Incidence of Lung and Bladder Cancer in Male Hairdressers in the Nordic Countries ~
~
Lung Norway Sweden Finland Denmark
~
~
Bladder
Obs
EXP
RR (95% CI)
Obs
EXP
RR (9.5%CI)
47 98 3 56
29.2 67.2 2.0 50.5
1.6 (1.2-2.1) 1.5 (1.2-1.8) 1.5 (0.3-4.4) 1.1 (0.9-1.4)
23 54 0 41
15.1 36.6 0.3 20.0
I .5 ( I .O-2.3) 1.5 (1.1-1.9) -~
2.1 (1.5-2.8)
TABLE IV. Incidence of Lung and Bladder Cancer in Female Hairdressers in the Nordic Countries ~~
Lung Norway Sweden Finland Denmark
~
Bladder
Oba
EXP
RR (95% CI)
Obs
EXP
RR (95% CI)
16
11.1 20.0 4.4 11.0
I .4 (0.8-2.3) 1.6 ( I . 1-2.2) 0.5 (0.1-1.7) 1.1 (0.6-1.9)
11
1.2 13.5 1.8 4.0
I.5 (0.8-2.8) 0.4 (0.2-1 .O) 1.7 (0.4-5.1) 1.8 (0.7-3.6)
31 2 12
6 3 7
to a rate of 12.4 per 100,000 in Finland, and among women, from 5.8 per 100,000 in Denmark to 2.7 per 100,000 in Finland [Jensen et al., 1988al. As the expected numbers of cancers for hairdressers are computed from national rates, this should not introduce bias. Smoking could not be controlled for on an individual basis, but the lack of excess risk for lung cancer among Danish hairdressers indicates that smoking is not the explanation for the excess risk of bladder cancer. In Sweden, survey data from 1963 indicate that smoking is more frequent among male barbers and beauticians than among Swedish males in general (74% vs. 46% in the age group 50-69 years) (J. Carstensen, personal communication). In accordance with this, we found increased risks for both lung and bladder cancer among male Swedish hairdressers. The same pattern was found among Norwegian male hairdressers, but here we have no survey data about smoking. In both countries RRs were around 1.5 for both cancers. If, for the sake of example, we assume that the relative risk for lung cancer among smokers compared to non-smokers is 10 and the relative risk for bladder cancer among smokers compared to non-smokers is 2, and furthermore that in a study group 74% are smokers and that in the reference group 46% are smokers, then this difference in smoking habits would give rise to a relative risk of 1.5 for lung cancer and 1.2 for bladder cancer [Axelson, 19781. Although the difference is not large, the finding among male hairdressers in Norway and Sweden of RRs around 1.5 for both cancers might indicate that bladder cancer risk slightly exceeds what can be ascribed to smoking. Hairdressing is a craft that is typically entered shortly after basic school education, i.e., at age 15-20 years. Few enter the craft after that age, whereas many leave thc craft and become housewives or take other jobs. Thus, age at census could be taken as a proxy for latency and duration of exposure, and the analysis could be restricted to thc age groups above 25 or 30 years. An analysis along these lines on the Danish bladder cancer data did not change the SMRs much, since no bladder cancer cases occurred in the younger age groups and the expected numbers of cancer cases
Occupational Risk for Cancer in Hairdressers
221
were low. By the same token, age at census could reflect changes in exposure over time, but the size of the study did not allow a detailed breakdown by age groups. The low risk for bladder cancer observed among female Swedish hairdressers may be a chance finding, even though a decreased RR of 0.6 (based on four cases) was already present in the 1973 follow-up [Malker and Weiner, 19841 and the RR for the period 1974-1979 is as low as 0.3 (based on two cases). There is a large turnover of female hairdressers in Sweden. More than one-half of the female hairdressers in Sweden at the time of the 1960 census were below 25 years of age. Thus, the duration of occupational exposure will be limited for most of the female hairdressers in Sweden, and selection in the turnover may also have lowered the RR. Still, the RR is low, since survey data from 1963 show a higher than average frequency of smokers among female hairdressers in Sweden (49% vs. 30% in the age group 18-49 years and 20% vs. 11% in the age group 50-69 years) (J. Carstensen, personal communication). Studies of Bladder Cancer Among Hairdressers
A cohort study of hairdressers from Geneva showed excess risk for bladder cancer among both males and females, although it was statistically significant for males only. The risk for lung cancer among the men was below unity [Gubkran et al., 19851. In a death certificate study of occupation and cancer, significantly elevated risk for bladder cancer was found among male hairdressers and cosmetologists [Dubrow and Wegman, 19841. Smoking was not controlled for. Six case-control studies of bladder cancer showed relative risks in the range 1.5 to 4.3, but none differed statistically significantly from unity [Wynder et al., 1963; Dunham et al., 1968; Anthony and Thomas, 1970; Howe et al., 1980; Silverman et al., 1983; Baxter and McDowall, 19861. Smoking was controlled for in three of these studies [Anthony and Thomas, 1970; Howe et al., 1980; Silverman et al., 19831. Two case-control studies of occupation and bladder cancer and cancer of the lower urinary tract showed relative risks among hairdressers below unity, although not statistically significant [Cole et al., 1972; Vineis and Magnani, 19851. Jensen et al. studied cancer of the urinary bladder and cancer of the renal pelvis and the ureter in the Copenhagen area in 1979-1982 separately. The relative risk for bladder cancers was 1.4 among male and 1.2 among female hairdressers (non-significant, smoking not controlled for, personal communication). The relative risk for cancer of the renal pelvis and ureter was 3.0 for female hairdressers (non-significant, smoking controlled for) [Jensen et al., 1987, 1988b1. In 1982, the International Agency for Research on Cancer surveyed the epidemiological evidence relevant to hair dyes and cancer. Studies of hairdressers were included in the survey because it was assumed that hairdressers constitute a group with high exposure to hair dyes. IARC concluded that the evidence relating bladder cancer or any other cancer to the occupation of hairdressing or to personal use of hair dyes was inconclusive [IARC, 19821. Hair dyes may not be the only potentially carcinogenic substances to which hairdressers have been exposed. Clemmesen drew attention to the content of butter yellow (para-Dimethylaminoazobenzene) in brillantine [Clemmesen, 1981; Williams, 19621. The so-called liquid brillantines consist for the major part of mineral, vegetable, or animal oil and deodorized kerosene, to which are added small quantities of
222
Skov et al.
color, perfume, and antioxidants. In the solid brilliantines, kerosene is substituted with various waxes. Para-Dimethylaminoazobenzene is carcinogenic in animals and is classified in group 2B by the International Agency for Research on Cancer [IARC, 1975, 19871. Reanalysis of data from a Danish case-control study of bladder cancer shows statistically significant excess risk (RR = 1.7) among users of brillantine as a hair lotion [Lockwood, 19611. Gubkran stated that application of brillantine after men’s haircut was customary among hairdressers in the Geneva area until about 1950 [Gubbran et al., 19851, but the study did not provide firm evidence to confirm a hypothesis relating bladder cancer to professional exposure to brillantine. Style of hairdressing and habits in relation to hairdressing is a part of national culture and, as such, subject to variation in time and among countries. Unfortunately all studies are based on the occupational title, and limited information is given on the specific occupational exposures. CONCLUSIONS
The risk of bladder cancer experienced by hairdressers in the Nordic countries adds to the unclear picture emerging from previous studies, possibly with some indication that the bladder cancer risk slightly exceeds what can be ascribed to smoking. As the occupational exposures involved in hairdressing may vary in time and between countries, it is conceivable that the lack of consistency among studies of bladder cancer among hairdressers, including the inconsistencies among the Nordic countries found in our study, may be due to differences in exposures at the work place. If these inconstencies are to be resolved, better smoking and exposure data are mandatory in future epidemiological studies. REFERENCES Andersen A, Bjelke E, Langmark F (1989): Cancer in waiters. Br J Cancer 60:112-115. Anthony HM, Thomas GM (1970): Tumors of the urinary bladder: An analysis of the occupations of 1,030 patients in Leeds, England. JNCI 455379-895. Axelson 0 (1978): Aspects on confounding in occupational health epidemiology. Scand J Work Environ Health 4:85-89. Bailar JC, Ederer F (1964): Significance factors for the ratio of a Poisson variable to its expectation. Biometrics 20:639-643. Baxter PJ, McDowall ME (1986): Occupation and cancer in London: An investigation into nasal and bladder cancer using the Cancer Atlas. Br J Ind Med 43:44-49. Clemmesen J (1981): Epidemiological studies into the possible carcinogenicity of hair dyes. Mutat Res 87:65 -79. Cole P, Hoover R, Friedell GH (1972): Occupation and cancer of the lower urinary tract. Cancer 29: 1250-1260. Dubrow R, Wegman DH (1984): Cancer and occupation in Massachusetts: A death certificate study. Am J Ind Med 6207-230. Dunham LJ, Rabson AS, Stewart HL, Frank AS (1968): Rates, interview, and pathology study of cancer of the urinary bladder in New Orleans, Louisiana. JNCI 41:683-709. Flamm WG (1985): Hair dyes: Laboratory evidence. In Wald NJ, Doll R (ed): ‘‘Interpretation of Negative Epidemiological Evidence for Carcinogenicity.” Lyon: IARC Scientific Publications Vol 65, pp 53-68. Green A, Willett WC, Colditz GA, Stampfer MJ, Bain C, Rosner B, Hennekens CH, Speizer FE (1987): Use of permanent hair dyes and risk of breast cancer. JNCI 79:253-257. Gubbran E, Raymond L, Sweetnam PM (1985): Increased risk for male bladder cancer among a cohort of male and female hairdressers from Geneva. Int J Epidemiol 14549-554.
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Hartge P, Hoover R, Altman R, Austin DF, Cantor KP, Child MA, Key CR, Mason TJ, Marrett LD, Myers MH, Narayana AS, Silverman DT, Sullivan JW, Swanson GM, Thomas DB, West DW (1982): Use of hair dyes and risk of bladder cancer. Cancer Res 42:4784-4787. Hennekens CH, Rosner B, Belanger C, Speizer FE, Bain CJ, Pet0 R (1979): Use of permanent hair dyes and cancer among registerd nurses. Lancet i: 1390-1393. Howe GR, Burch JD, Miller AB, Cook GM, Esteve J, Morrison B, Gordon P, Chambers LW, Fodor G , Winsor GM ( 1980): Tobacco use, occupation, coffee, various nutrients, and bladder cancer. JNCI 64:70 1-7 13. International Agency for Research on Cancer (1975): Some Aromatic Azo Compounds. In “IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans, 8.” Lyon: IARC, pp 56-61, International Agency for Research on Cancer (1982): Epidemiological evidence relating to the possible carcinogenic effects of hair dyes in hairdressers and users of hair dyes. In “IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans” 27: Appendix 1. Lyon: IARC, pp 307-3 18. International Agency for Research on Cancer (1987): Overall evaluations of carcinogenicity: An updating of IARC Monographs volumes 1 to 42. “IARC Monographs on the Evaluation of Carcinogenic Risks to Humans:” suppl 7. Lyon: IARC, p 390. Jain M, Morgan RW, Elinson L (1977): Hair dyes and bladder cancer. Can Med Assoc J 117:1131-1133. Jensen OM, Wahrendorf J, Knudsen JB, Sorensen BL (1987): The Copenhagen case-referent study on bladder cancer: Risk among drivers, painters and certain other occupations. Scand J Work Eviron Health 13:129-134. Jensen OM, Carstensen B, Glattre E, Malker B, Pukkala E, Tulinius H (1988a): “Atlas of Cancer Incidence in the Nordic Countries. ” Copenhagen: Nordic Cancer Union. Jensen OM, Knudsen JB, McLaughlin JK, Sorensen BL (1988b): The Copenhagen case-control study of renal pelvis and ureter cancer: Role of smoking and occupational exposures. Int J Cancer 41: 557-561. Kinlen LJ, Harris R, Garrod A, Rodrequez K (1977): Use of hair dyes by patients with breast cancer: A case-control study. Br Med [Clin Res] J 2:366-368. Lockwood K (1961): On the etiology of bladder tumors in Kobenhavn-Frederiksberg. An inquiry of 369 patients and 369 controls. Acta Path01 Microbiol Immunol Scand [Suppl] 145:1-165. Lynge E, Thygesen L (1988): Use of surveillance systems for occupational cancer: Data from the Danish national system. Int J Epidemiol 17:493-500. Malker H (1988): Register-epidemiology in the identification of cancer risks. Arbete och Halasa 21: 1-50. Malker H, Weiner J (1984): The Cancer-Environment Registry 1961-1973. Examples of the use of register epidemiology in studies of the work environment. Arbete och Halsa 9: 1-107 (in Swedish). Malker HSR, McLaughlin JK, Silverman DT, Ericsson JLE, Stone BJ, Weiner JA, Malker BK, Blott JW (1987): Occupational risk for bladder cancer among men in Sweden. Cancer Res 47:6763-6766. Nasca PC, Lawrence CE, Greenwald P, Chorost S , Arbuckle JT, Paulson A (1980):Relationship of hair dye use, benign breast disease, and breast cancer. JNCI 64:23-28. Neutel CI, Nair RC, Last JM (1978): Are hair dyes associated with bladder cancer? Can Med Assoc J 119:307,308. Pukkala E, Teppo L, Hakulinen T, Rimpela M (1983): Occupation and smoking as risk determinants of lung cancer. Int J Epidemiol 12:290-296. Shafer N, Shafer RW (1976): Potential of carcinogenic effects of hair dyes. NY State J Med 76:394-396. Shore RE, Pasternack BS, Thiessen EU, Sadow M, Forbes R, Albert RE (1979): A case-control study of hair dye use and breast cancer. JNCl 62:277-283. Silverman DT, Hoover RN, Albert S, Graff KM (1983): Occupation and cancer of the lower urinary tract in Detroit. JNCI 70:237-245. Vineis P, Magnani C (1985): Occupation and bladder cancer in males: A case-control study. Int J Cancer 35:599-606. Williams MHC (1962): Environmental and industrial bladder cancer. Preventative measures. Acta Unio Internationalis Contra Cancrum 18:676-683. World Health Organization (1957): “International Classification of Diseases. ” Geneva: WHO. Wynder EL, Goodman M (1983): Epidemiology of breast cancer and hair dyes. JNCI 71(3):481-488. Wynder EL, Onderdonk J, Mantel N (1963): An epidemiological investigation of cancer of the bladder. Cancer 16:1388-1407.
Risk for Cancer of the Urinary Bladder Among Hairdressers in the Nordic Countries Torsten Skov, MD,Aage Andersen, MD, Hans Malker, PhD, Eero Pukkala, PhD, Jan Weiner, MS, and Elsebeth Lynge, MD
Several studies have indicated an increased risk for cancer of the urinary bladder among hairdressers. In a Danish linkage between census data and cancer register data both male and female hairdressers have an elevated risk for bladder cancer. The risk for lung cancer is close to unity, indicating that occupational factors rather than smoking, may be responsible lor the increased risk for bladder cancer among hairdressers. To evaluate this hypothesis we conducted a collaborative analysis of data from similar linkages in Finland, Norway, and Sweden. The combination of high risk for bladder cancer and low or no risk for lung cancer was not found in the other Nordic countries; however, statistically significant increased risks for both bladder and lung cancer were found among male hairdressers in both Norway and Sweden. The relative risks for bladder cancer were of the same magnitude as the relative risks for lung cancer. Key words: occupational cancer register, hair dyes, bladder cancer risk, occupational exposure
INTRODUCTION
Several hair dye ingredients are carcinogenic to animals [IARC, 1982; Flamm, 19851. The impact of the widespread non-occupational use of hair dye preparations has been extensively studied with special attention to cancer of the breast and, to a lesser extent, cancer of the bladder [Shafer and Shafer, 1976; Kinlen et al., 1977; Hennekens et al., 1979; Shore et al., 1979; Nasca et al., 1980; Wynder and Goodman, 1983; Green et al., 1987; Jain et al., 1977; Neutel et al., 1978; Hartge et al., 19821. Taken together these studies do not show any excess risk for cancer from non-occupational use of hair dyes. Several studies have shown elevated risk for bladder cancer among hairdressers, barbers, or beauticians [Wynder et al., 1963; Dunham et al., 1968; Anthony and Thomas, 1970; Howe et al., 1980; Silverman et al., 1983; Malker and Weiner, 1984; Dubrow and Wegman, 1984; Gubkran et al., 1985; Baxter and McDowall, 1986; Malker et al., 19871, but other studies have been
Danish Cancer Society, Danish Cancer Registry, Copenhagen, Denmark (T.S., E.L.). Norwegian Cancer Registry, Oslo, Norway (A.A.). National Board of Occupational Safety and Health, Solna, Sweden (H.M., J.W.). Finnish Cancer Registry, Helsinki, Finland (E.P.). Address reprint requests to Dr. T. Skov, Danish Cancer Society, Danish Cancer Registry, Rosenvaengets Hovedvej 35, Box 839, DK-2100 Copenhagen, Denmark. Accepted for publication September 13, 1989.
0 1990 Wiley-Liss, Inc.
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TABLE I. Design of the Nordic Occupational Cancer Studies
Country Census
Population studied
Norway
1960 15-69 years, economically active at census Sweden 1960 All ages, economically active at census Finland 1970 25-64 years at some time during follow-up, economically active at census Denmark 1970 20-64 years, economically active at census
Birth cohorts covered
Follow-~p period
Reference population
1891-1945
1961-84
All economically active
No restriction
1961-79
1906-1955”
1971-80
Total population in same region All economically active
1906-1950
1970-80
All economically active
“Birth cohorts 1906-1915 and 1946-1955 only partially covered, see “Materials and Methods.”
negative [Cole et al., 1972; Vineis and Magnani, 19851. Data from the Danish occupational cancer register-a linkage between census information and cancer register information-show that both male and female hairdressers experience an increased risk for bladder cancer and a risk for lung cancer close to unity [Lynge and Thygesen, 19881. The lack of an excess in the lung cancer risk indicates that factors other than smoking may be responsible for the excess risk for bladder cancer among Danish hairdressers. Linkage of census data with data from the national cancer registers has been undertaken in Finland, Sweden, Norway, and Denmark. The existence of these linked data offered an exellent opportunity to examine whether the pattern of cancer risk found among Danish hairdressers could also be found in the other Nordic countries. MATERIALS AND METHODS In four of the Nordic countries, Denmark, Finland, Norway, and Sweden, cross-sectionally registered census populations have been followed up for cancer incidence by individual record linkage. The census populations and follow-up periods of the study populations in the four countries are shown in Table I. Industry and occupation refer to the status at the time of the census [Pukkala et al., 1983; Malker, 1988; Lynge and Thygesen, 1988; Andersen et al., 19891. Hairdressers were identified by combining codes for occupation and industry (see Table 11). In all four countries all cancer cases during the follow-up period were coded according to ICD-7 [World Health Organization, 19571. Lung cancer includes only primary lung cancer (ICD-7 162.0,1), and bladder cancer includes invasive carcinoma (ICD-7 181.O) and papilloma, whether benign or malignant. The completeness of reporting of papillomas may vary among countries [Jensen et al., 1988aI. In Denmark the study population was restricted to persons aged 20-64 years at the 1970 census, in Norway to persons aged 15-69 years at the 1960 census, and in Finland to persons aged 25-69 years at any time during the follow-up period. In these countries the expected number of bladder cancer and lung cancer cases was calculated by multiplying the person-years at risk for each of the 5-year birth cohorts of male and female hairdressers with the sex-specific incidence rate for the equivalent 5-year birth
Occupational Risk for Cancer in Hairdressers
219
TABLE 11. Number of Hairdressers in the Nordic Studies ~~
Countrv
Industry code
Occupation code and descriution
No. of males
No. of females
941 hairdressers and beauticians 941 hairdressers and beauticians 840 hairdressers and barbers 395 hairdressers and barbers 01 1-040 self-employed
2, I49 6,522 428 1,177 3,697
4,356 16,942 9,138 4,160 5,337
13,973
39,933
~~
Norway Sweden Finland Denmark Denmark Total
All All All All 86 1 hairdresser
cohort of all persons who were economically active at the time of the census. In Sweden the study population was not age restricted. The expected number of bladder and lung cancer cases was calculated by multiplying the number of male and female hairdressers in a given region of Sweden in each 5-year birth cohort at the time of the census, with the sex-specific estimated disease probability for the equivalent 5-year birth cohort of all persons in the region. National figures were obtained by aggregating both observed and expected numbers across the 27 Swedish regions (24 counties and 3 largest cities). The observed number of cases divided by the expected number was used as an index of the relative risk (RR) in all four countries. Confidence intervals (CIS), 95%, were calculated under the assumption that the observed numbers of cancer cases followed a Poisson distribution [Bailar and Ederer, 19641. RESULTS The total number of hairdressers in the study series was 54,000 (Table 11). In Finland, hairdressing is clearly a woman’s job with 96% of hairdressers being female; in the other Nordic countries, at least two-thirds of the hairdressers were women. Male hairdressers in Norway and Sweden experienced a significantly increased relative risk for both bladder and lung cancer (Table 111). Among Danish male hairdressers the risk for bladder cancer was significantly increased, whereas the risk for lung cancer was 1.1. Finnish male hairdressers were so few that they had only three cases of lung cancer and no cases of bladder cancer. Table IV shows that the risk for bladder and lung cancer among female Norwegian hairdressers resembled that of their male counterparts, namely RRs for both cancers around 1.5. Swedish female hairdressers experienced a significantly increased risk for lung cancer and a decreased risk for bladder cancer. The numbers of cancer cases among Finnish female hairdressers were small, but the risks bear resemblance to those in Denmark, with increased risk for bladder cancer and decreased or unity risk for lung cancer. DISCUSSION
The combination observed among Danish hairdressers of low or unity risk for lung cancer and increased risk for bladder cancer was not found in the other Nordic countries except for female hairdressers in Finland where the numbers were small. The incidence of bladder cancer varies greatly among the Nordic countries; among men, it ranges from an age-standardized rate of 22.9 per 100,000 in Denmark
220
Skov et al.
TABLE 111. Incidence of Lung and Bladder Cancer in Male Hairdressers in the Nordic Countries ~
~
Lung Norway Sweden Finland Denmark
~
~
Bladder
Obs
EXP
RR (95% CI)
Obs
EXP
RR (9.5%CI)
47 98 3 56
29.2 67.2 2.0 50.5
1.6 (1.2-2.1) 1.5 (1.2-1.8) 1.5 (0.3-4.4) 1.1 (0.9-1.4)
23 54 0 41
15.1 36.6 0.3 20.0
I .5 ( I .O-2.3) 1.5 (1.1-1.9) -~
2.1 (1.5-2.8)
TABLE IV. Incidence of Lung and Bladder Cancer in Female Hairdressers in the Nordic Countries ~~
Lung Norway Sweden Finland Denmark
~
Bladder
Oba
EXP
RR (95% CI)
Obs
EXP
RR (95% CI)
16
11.1 20.0 4.4 11.0
I .4 (0.8-2.3) 1.6 ( I . 1-2.2) 0.5 (0.1-1.7) 1.1 (0.6-1.9)
11
1.2 13.5 1.8 4.0
I.5 (0.8-2.8) 0.4 (0.2-1 .O) 1.7 (0.4-5.1) 1.8 (0.7-3.6)
31 2 12
6 3 7
to a rate of 12.4 per 100,000 in Finland, and among women, from 5.8 per 100,000 in Denmark to 2.7 per 100,000 in Finland [Jensen et al., 1988al. As the expected numbers of cancers for hairdressers are computed from national rates, this should not introduce bias. Smoking could not be controlled for on an individual basis, but the lack of excess risk for lung cancer among Danish hairdressers indicates that smoking is not the explanation for the excess risk of bladder cancer. In Sweden, survey data from 1963 indicate that smoking is more frequent among male barbers and beauticians than among Swedish males in general (74% vs. 46% in the age group 50-69 years) (J. Carstensen, personal communication). In accordance with this, we found increased risks for both lung and bladder cancer among male Swedish hairdressers. The same pattern was found among Norwegian male hairdressers, but here we have no survey data about smoking. In both countries RRs were around 1.5 for both cancers. If, for the sake of example, we assume that the relative risk for lung cancer among smokers compared to non-smokers is 10 and the relative risk for bladder cancer among smokers compared to non-smokers is 2, and furthermore that in a study group 74% are smokers and that in the reference group 46% are smokers, then this difference in smoking habits would give rise to a relative risk of 1.5 for lung cancer and 1.2 for bladder cancer [Axelson, 19781. Although the difference is not large, the finding among male hairdressers in Norway and Sweden of RRs around 1.5 for both cancers might indicate that bladder cancer risk slightly exceeds what can be ascribed to smoking. Hairdressing is a craft that is typically entered shortly after basic school education, i.e., at age 15-20 years. Few enter the craft after that age, whereas many leave thc craft and become housewives or take other jobs. Thus, age at census could be taken as a proxy for latency and duration of exposure, and the analysis could be restricted to thc age groups above 25 or 30 years. An analysis along these lines on the Danish bladder cancer data did not change the SMRs much, since no bladder cancer cases occurred in the younger age groups and the expected numbers of cancer cases
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were low. By the same token, age at census could reflect changes in exposure over time, but the size of the study did not allow a detailed breakdown by age groups. The low risk for bladder cancer observed among female Swedish hairdressers may be a chance finding, even though a decreased RR of 0.6 (based on four cases) was already present in the 1973 follow-up [Malker and Weiner, 19841 and the RR for the period 1974-1979 is as low as 0.3 (based on two cases). There is a large turnover of female hairdressers in Sweden. More than one-half of the female hairdressers in Sweden at the time of the 1960 census were below 25 years of age. Thus, the duration of occupational exposure will be limited for most of the female hairdressers in Sweden, and selection in the turnover may also have lowered the RR. Still, the RR is low, since survey data from 1963 show a higher than average frequency of smokers among female hairdressers in Sweden (49% vs. 30% in the age group 18-49 years and 20% vs. 11% in the age group 50-69 years) (J. Carstensen, personal communication). Studies of Bladder Cancer Among Hairdressers
A cohort study of hairdressers from Geneva showed excess risk for bladder cancer among both males and females, although it was statistically significant for males only. The risk for lung cancer among the men was below unity [Gubkran et al., 19851. In a death certificate study of occupation and cancer, significantly elevated risk for bladder cancer was found among male hairdressers and cosmetologists [Dubrow and Wegman, 19841. Smoking was not controlled for. Six case-control studies of bladder cancer showed relative risks in the range 1.5 to 4.3, but none differed statistically significantly from unity [Wynder et al., 1963; Dunham et al., 1968; Anthony and Thomas, 1970; Howe et al., 1980; Silverman et al., 1983; Baxter and McDowall, 19861. Smoking was controlled for in three of these studies [Anthony and Thomas, 1970; Howe et al., 1980; Silverman et al., 19831. Two case-control studies of occupation and bladder cancer and cancer of the lower urinary tract showed relative risks among hairdressers below unity, although not statistically significant [Cole et al., 1972; Vineis and Magnani, 19851. Jensen et al. studied cancer of the urinary bladder and cancer of the renal pelvis and the ureter in the Copenhagen area in 1979-1982 separately. The relative risk for bladder cancers was 1.4 among male and 1.2 among female hairdressers (non-significant, smoking not controlled for, personal communication). The relative risk for cancer of the renal pelvis and ureter was 3.0 for female hairdressers (non-significant, smoking controlled for) [Jensen et al., 1987, 1988b1. In 1982, the International Agency for Research on Cancer surveyed the epidemiological evidence relevant to hair dyes and cancer. Studies of hairdressers were included in the survey because it was assumed that hairdressers constitute a group with high exposure to hair dyes. IARC concluded that the evidence relating bladder cancer or any other cancer to the occupation of hairdressing or to personal use of hair dyes was inconclusive [IARC, 19821. Hair dyes may not be the only potentially carcinogenic substances to which hairdressers have been exposed. Clemmesen drew attention to the content of butter yellow (para-Dimethylaminoazobenzene) in brillantine [Clemmesen, 1981; Williams, 19621. The so-called liquid brillantines consist for the major part of mineral, vegetable, or animal oil and deodorized kerosene, to which are added small quantities of
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color, perfume, and antioxidants. In the solid brilliantines, kerosene is substituted with various waxes. Para-Dimethylaminoazobenzene is carcinogenic in animals and is classified in group 2B by the International Agency for Research on Cancer [IARC, 1975, 19871. Reanalysis of data from a Danish case-control study of bladder cancer shows statistically significant excess risk (RR = 1.7) among users of brillantine as a hair lotion [Lockwood, 19611. Gubkran stated that application of brillantine after men’s haircut was customary among hairdressers in the Geneva area until about 1950 [Gubbran et al., 19851, but the study did not provide firm evidence to confirm a hypothesis relating bladder cancer to professional exposure to brillantine. Style of hairdressing and habits in relation to hairdressing is a part of national culture and, as such, subject to variation in time and among countries. Unfortunately all studies are based on the occupational title, and limited information is given on the specific occupational exposures. CONCLUSIONS
The risk of bladder cancer experienced by hairdressers in the Nordic countries adds to the unclear picture emerging from previous studies, possibly with some indication that the bladder cancer risk slightly exceeds what can be ascribed to smoking. As the occupational exposures involved in hairdressing may vary in time and between countries, it is conceivable that the lack of consistency among studies of bladder cancer among hairdressers, including the inconsistencies among the Nordic countries found in our study, may be due to differences in exposures at the work place. If these inconstencies are to be resolved, better smoking and exposure data are mandatory in future epidemiological studies. REFERENCES Andersen A, Bjelke E, Langmark F (1989): Cancer in waiters. Br J Cancer 60:112-115. Anthony HM, Thomas GM (1970): Tumors of the urinary bladder: An analysis of the occupations of 1,030 patients in Leeds, England. JNCI 455379-895. Axelson 0 (1978): Aspects on confounding in occupational health epidemiology. Scand J Work Environ Health 4:85-89. Bailar JC, Ederer F (1964): Significance factors for the ratio of a Poisson variable to its expectation. Biometrics 20:639-643. Baxter PJ, McDowall ME (1986): Occupation and cancer in London: An investigation into nasal and bladder cancer using the Cancer Atlas. Br J Ind Med 43:44-49. Clemmesen J (1981): Epidemiological studies into the possible carcinogenicity of hair dyes. Mutat Res 87:65 -79. Cole P, Hoover R, Friedell GH (1972): Occupation and cancer of the lower urinary tract. Cancer 29: 1250-1260. Dubrow R, Wegman DH (1984): Cancer and occupation in Massachusetts: A death certificate study. Am J Ind Med 6207-230. Dunham LJ, Rabson AS, Stewart HL, Frank AS (1968): Rates, interview, and pathology study of cancer of the urinary bladder in New Orleans, Louisiana. JNCI 41:683-709. Flamm WG (1985): Hair dyes: Laboratory evidence. In Wald NJ, Doll R (ed): ‘‘Interpretation of Negative Epidemiological Evidence for Carcinogenicity.” Lyon: IARC Scientific Publications Vol 65, pp 53-68. Green A, Willett WC, Colditz GA, Stampfer MJ, Bain C, Rosner B, Hennekens CH, Speizer FE (1987): Use of permanent hair dyes and risk of breast cancer. JNCI 79:253-257. Gubbran E, Raymond L, Sweetnam PM (1985): Increased risk for male bladder cancer among a cohort of male and female hairdressers from Geneva. Int J Epidemiol 14549-554.
Occupational Risk for Cancer in Hairdressers
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Hartge P, Hoover R, Altman R, Austin DF, Cantor KP, Child MA, Key CR, Mason TJ, Marrett LD, Myers MH, Narayana AS, Silverman DT, Sullivan JW, Swanson GM, Thomas DB, West DW (1982): Use of hair dyes and risk of bladder cancer. Cancer Res 42:4784-4787. Hennekens CH, Rosner B, Belanger C, Speizer FE, Bain CJ, Pet0 R (1979): Use of permanent hair dyes and cancer among registerd nurses. Lancet i: 1390-1393. Howe GR, Burch JD, Miller AB, Cook GM, Esteve J, Morrison B, Gordon P, Chambers LW, Fodor G , Winsor GM ( 1980): Tobacco use, occupation, coffee, various nutrients, and bladder cancer. JNCI 64:70 1-7 13. International Agency for Research on Cancer (1975): Some Aromatic Azo Compounds. In “IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans, 8.” Lyon: IARC, pp 56-61, International Agency for Research on Cancer (1982): Epidemiological evidence relating to the possible carcinogenic effects of hair dyes in hairdressers and users of hair dyes. In “IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans” 27: Appendix 1. Lyon: IARC, pp 307-3 18. International Agency for Research on Cancer (1987): Overall evaluations of carcinogenicity: An updating of IARC Monographs volumes 1 to 42. “IARC Monographs on the Evaluation of Carcinogenic Risks to Humans:” suppl 7. Lyon: IARC, p 390. Jain M, Morgan RW, Elinson L (1977): Hair dyes and bladder cancer. Can Med Assoc J 117:1131-1133. Jensen OM, Wahrendorf J, Knudsen JB, Sorensen BL (1987): The Copenhagen case-referent study on bladder cancer: Risk among drivers, painters and certain other occupations. Scand J Work Eviron Health 13:129-134. Jensen OM, Carstensen B, Glattre E, Malker B, Pukkala E, Tulinius H (1988a): “Atlas of Cancer Incidence in the Nordic Countries. ” Copenhagen: Nordic Cancer Union. Jensen OM, Knudsen JB, McLaughlin JK, Sorensen BL (1988b): The Copenhagen case-control study of renal pelvis and ureter cancer: Role of smoking and occupational exposures. Int J Cancer 41: 557-561. Kinlen LJ, Harris R, Garrod A, Rodrequez K (1977): Use of hair dyes by patients with breast cancer: A case-control study. Br Med [Clin Res] J 2:366-368. Lockwood K (1961): On the etiology of bladder tumors in Kobenhavn-Frederiksberg. An inquiry of 369 patients and 369 controls. Acta Path01 Microbiol Immunol Scand [Suppl] 145:1-165. Lynge E, Thygesen L (1988): Use of surveillance systems for occupational cancer: Data from the Danish national system. Int J Epidemiol 17:493-500. Malker H (1988): Register-epidemiology in the identification of cancer risks. Arbete och Halasa 21: 1-50. Malker H, Weiner J (1984): The Cancer-Environment Registry 1961-1973. Examples of the use of register epidemiology in studies of the work environment. Arbete och Halsa 9: 1-107 (in Swedish). Malker HSR, McLaughlin JK, Silverman DT, Ericsson JLE, Stone BJ, Weiner JA, Malker BK, Blott JW (1987): Occupational risk for bladder cancer among men in Sweden. Cancer Res 47:6763-6766. Nasca PC, Lawrence CE, Greenwald P, Chorost S , Arbuckle JT, Paulson A (1980):Relationship of hair dye use, benign breast disease, and breast cancer. JNCI 64:23-28. Neutel CI, Nair RC, Last JM (1978): Are hair dyes associated with bladder cancer? Can Med Assoc J 119:307,308. Pukkala E, Teppo L, Hakulinen T, Rimpela M (1983): Occupation and smoking as risk determinants of lung cancer. Int J Epidemiol 12:290-296. Shafer N, Shafer RW (1976): Potential of carcinogenic effects of hair dyes. NY State J Med 76:394-396. Shore RE, Pasternack BS, Thiessen EU, Sadow M, Forbes R, Albert RE (1979): A case-control study of hair dye use and breast cancer. JNCl 62:277-283. Silverman DT, Hoover RN, Albert S, Graff KM (1983): Occupation and cancer of the lower urinary tract in Detroit. JNCI 70:237-245. Vineis P, Magnani C (1985): Occupation and bladder cancer in males: A case-control study. Int J Cancer 35:599-606. Williams MHC (1962): Environmental and industrial bladder cancer. Preventative measures. Acta Unio Internationalis Contra Cancrum 18:676-683. World Health Organization (1957): “International Classification of Diseases. ” Geneva: WHO. Wynder EL, Goodman M (1983): Epidemiology of breast cancer and hair dyes. JNCI 71(3):481-488. Wynder EL, Onderdonk J, Mantel N (1963): An epidemiological investigation of cancer of the bladder. Cancer 16:1388-1407.
