Dec 27, 2005 - Occupational cancer risks suggested among food industry workers are inconclusive. The objective of our study was to assess associa-.
Int. J. Cancer: 118, 2567–2571 (2006) ' 2005 Wiley-Liss, Inc.
Cancer risk among Finnish food industry workers Aarne Laakkonen1*, Timo Kauppinen1 and Eero Pukkala2 1 Finnish Institute of Occupational Health, Helsinki, Finland 2 Finnish Cancer Registry, Institute for Statistical and Epidemiological Cancer Research, Helsinki, Finland Occupational cancer risks suggested among food industry workers are inconclusive. The objective of our study was to assess associations between different cancers and working in the food industry in Finland. The carcinogenic exposures are mainly inhalatory, and we were therefore interested in respiratory cancers in particular. We followed up a cohort of all economically active Finns born between 1906 and 1945 for 30 million person-years during 1971–95. The 1970 Census data on occupations were linked with data on subsequent incident cancer cases. Standardized incidence ratios (SIR) and 95% confidence intervals (CI) were calculated for each occupation using the economically active population as the reference. A total of 2,526 incident cancer cases were observed. Elevated risks were observed among male food industry workers for pancreatic (SIR 5 1.50, CI 5 1.13–1.96) and kidney cancers (1.51, 1.16–1.94). With respect to specific occupations, there was an excess of lung cancer among female bakers (1.38, 1.01–1.85) and laryngeal cancer among male grain millers (2.60, 1.05–5.36). Occupational exposure is unlikely to be a major risk factor for cancer among Finnish workers employed in typical food industry occupations. ' 2005 Wiley-Liss, Inc. Key words: cancer; food industry; occupational exposure
The food industry covers a series of industrial activities involving processing, conversion, preparation, preservation and packaging of foodstuffs. The raw materials used are generally of vegetable or animal origin and produced by farming, breeding and fishing. Respiratory disorders, skin diseases and contact allergies, hearing impairment and musculoskeletal disorders are among the most common occupational health problems in the food industry.1 There were 4.4 million workers in the food industries in the European Union (EU25, population 459 million2) in 2001, and with a value added of EUR 175.6 billion recorded by structural business statistics, it was the second largest manufacturing sector after metal industry.3 At the same time, there were 19,000 Finns employed in typical food industry occupations.4,5 According to the International Information System on Occupational Exposure to Carcinogens (CAREX), 12% of food manufacturing employees and 14% of beverage industry employees in EU (EU15) were potentially exposed to carcinogens in 1990–93.6 CAREX includes exposure data on agents evaluated by the International Agency for Research on Cancer (IARC) displayed across 55 industrial classes. The major carcinogenic exposures in the food manufacturing industry according to CAREX were asbestos, chromium VI compounds, environmental tobacco smoke, nickel compounds, polycyclic aromatic hydrocarbons, radon and solar radiation. Carcinogens are seldom used in the actual manufacturing processes, except in the production of smoked foods, but exposure takes place mainly in service and maintenance activities (chromium, nickel, and asbestos) or as an environmental exposure (radon in indoor work in some regions and solar radiation in regular outdoor work). Several studies on the relationship between occupations in the food industry and cancer have been performed, but only suggestions of occupational exposure as a causal factor have been found. The objective of the present study was to assess associations between different cancers and working in typical food industry occupations in Finland. The possible carcinogenic exposures in the food industry are predominantly inhalatory, and we were therefore particularly interested in respiratory cancers. We also investigated all main other sites of cancer among food industry workers as hypothesis generation. Publication of the International Union Against Cancer
Material and methods The study cohort comprised all economically active Finns born between 1906 and 1945 who participated in the national population census on 31 December 1970 (667,121 men; 513,110 women). The census files are maintained at Statistics Finland and updated for vital status to allow exact person-year calculation. Data on the occupation held for the longest period in 1970 were obtained from the Population Census records.7 The occupational classification is based on the Nordic Classification of Occupations, which is compiled on the basis of the International Standard Classification of Occupations (ISCO) published in 1958 by the International Labor Organization (ILO).8 The socioeconomic status (SES) for each subject was based on the subject’s own occupation. In our analyses, the SES was categorized as farmers, higher whitecollar, clerical, skilled blue-collar and unskilled workers. The Finnish Cancer Registry (FCR) has collected data on all cancer cases diagnosed in Finland since 1953. All physicians, hospitals and other institutions, and all pathologic, cytological and hematological laboratories in the country must notify the FCR of all cancer cases that come to their attention. In addition, Statistics Finland annually provides a computerized file on death certificates in which cancer is mentioned. The FCR coverage is virtually complete and the data accuracy high.9,10 In this study, the incident cases of all cancers diagnosed during 1971–95 among persons born 1906–45 were extracted from the FCR and linked with the Statistics Finland Population Census 1970 file. Since 1967, every person residing in Finland has been assigned a unique 11-digit personal identifier (PID), which facilitates reliable computerized record linkages. Occupational exposure of the cohort was described by using Finnish job-exposure Matrix (FINJEM),4,5 which covers major occupational exposures in Finland since 1945 by occupation and calendar time. Exposure is characterized by the proportion of exposed persons (P) and the average level of exposure (L) among the exposed persons in each occupation. The estimates are based on exposure measurements, hazard surveys and the judgements by occupational hygienists. In the present study, the exposure period of FINJEM used was 1960–84. The occupations in the food industry and their major FINJEM-exposures are presented in Table I. The observed and expected numbers of all cancer cases of all sites for every occupation in the food industry were calculated for
Abbreviations: CAREX, International Information System on Occupational Exposure to Carcinogens; CI, confidence interval; CLL, chronic lymphatic leukaemia; EU15, European Union with 15 member states; EU25, European Union with 25 member states; FCR, Finnish Cancer Registry; FINJEM, Finnish Job-Exposure Matrix; IARC, The International Agency for Research on Cancer; ILO, International Labour Organization; L, average level of exposure among exposed persons; N, number of persons; O, observed number of cases; P, proportion of exposed persons; PID, personal identifier; SES, socioeconomic status; SIR, standardized incidence ratio. Grant sponsor: Finnish Work Environment Fund; Grant number: 105037. *Correspondence to: Finnish Institute of Occupational Health, Department of Epidemiology and Biostatistics, Topeliuksenkatu 41 a A, FIN00250 Helsinki, Finland. Fax: 1358 10 381 2711. E-mail: aarne.laakkonen@kolumbus.fi Received 31 May 2005; Accepted after revision 12 October 2005 DOI 10.1002/ijc.21702 Published online 27 December 2005 in Wiley InterScience (www. interscience.wiley.com).
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LAAKKONEN ET AL. TABLE I – OCCUPATION, NUMBER OF EMPLOYED IN CENSUS 1970 (N), MAJOR CHEMICAL AND BIOLOGICAL INHALATORY EXPOSURES, PROPORTION OF EXPOSED PERSONS (P; %) AND AVERAGE EXPOSURE LEVEL (L) IN 1960–84, ACCORDING TO FINJEM4 Occupation
N
Grain millers
Agent
Dairy workers Processed food workers Sugar processing workers Other occupations in the food industry
Unit
1391
45 67 87 9 4
17 3 3 1 1
mg/m3 mg/m3 mg/m3 mg/m3 mg/m3
1398
Plant dust
3
5
mg/m3
1263 5136
None Flour dust Carbon monoxide None Flour dust None Flour dust Plant dust Moulds Bacteria
2 2
10 5
mg/m3 Ppm
16
5
mg/m3
12 33 10 10
10 1 100 7700
mg/m3 mg/m3 cfu/m3 cfu/m3
11488
Chocolate and confectionery manufacturers Brewers, beverage makers and kilnmen Cannery workers Butchers and sausage makers
L
Flour dust Plant dust Flour dust Plant dust Plant dust
1343
Bakers
P
5230 962 495 851
TABLE II – OCCUPATIONS IN THE FOOD INDUSTRY, OBSERVED (O) AND EXPECTED (E) NUMBERS OF ALL CANCERS, AND OF LUNG CANCERS, STANDARDIZED INCIDENCE RATIO (SIR) AND ITS 95% CONFIDENCE INTERVAL (CI) IN 1971–95 All sites Occupation
Grain millers Bakers Chocolate and confectionery manufacturers Brewers, beverage makers and kilnmen Cannery workers Butchers and sausage makers Dairy workers Processed food workers Sugar processing workers Other occupations in the food industry
Lung cancer
Men
Women
Men
Women
O
E
SIR
95% CI
O
E
SIR
95% CI
O
E
SIR
95% CI
O
E
SIR
95% CI
173 235 24
152.7 230.3 25.5
1.13 1.02 0.94
0.97–1.31 0.89–1.16 0.60–1.40
11 683 106
8.1 731.7 100.7
1.36 0.93 1.05
0.68–2.43 0.86–1.00 0.86–1.26
41 53 6
39.2 55.2 6.7
1.05 0.96 0.90
0.75–1.42 0.72–1.25 0.33–1.95
0 45 4
0.4 32.6 4.4
0 1.38 0.91
0.00–10.2 1.01–1.85 0.25–2.33
56
51.7
1.08
0.82–1.41
75
69.8
1.07
0.85–1.35
12
13.6
0.88
0.46–1.54
3
3.0
0.99
0.20–2.88
36 257
40.3 253.6
0.89 1.01
0.63–1.24 0.89–1.14
80 151
76.4 137.8
1.05 1.10
0.83–1.30 0.93–1.28
6 65
10.5 65.3
0.57 1.00
0.21–1.24 0.77–1.27
7 9
3.5 6.1
1.99 1.47
0.80–4.10 0.67–2.79
101 5 47 55
122.9 4.8 44.1 40.8
0.82 1.03 1.07 1.35
0.67–0.99 0.34–2.41 0.78–1.42 1.02–1.76
301 82 9 39
326.0 72.6 12.5 40.9
0.92 1.13 0.72 0.95
0.82–1.03 0.90–1.40 0.33–1.37 0.68–1.30
23 2 10 13
32.3 1.3 12.0 10.9
0.71 1.51 0.84 1.19
0.45–1.07 0.18–5.46 0.40–1.54 0.63–2.03
7 2 2 1
13.9 3.2 0.6 1.8
0.50 0.62 3.51 0.55
0.20–1.04 0.07–2.24 0.42–12.7 0.01–3.04
each 5-year calendar period, 5-year birth cohort, gender and SES. The expected number in each stratum was calculated by multiplying the number of person-years with the incidence rate of each cancer site of the entire economically active Finnish population in the respective stratum. The standardized incidence ratio (SIR) was defined as the ratio of observed to expected number of cases. The 95% confidence interval (CI) was calculated for the SIR. The respiratory cancers studied were nasal cancer, laryngeal cancer and lung cancer. Our selection of all sites included 32 main categories of cancer. Results There were 989 cases of cancer among men and 1537 cases among women of the cohort. The SIR for all cancers was 1.02 (CI 5 0.96–1.09) for men and 0.97 (0.93–1.02) for women. There was an excess of pancreatic cancer (SIR 5 1.50, CI 5 1.13–1.96) and kidney cancer (1.51, 1.16–1.94) among male food industry workers, but no statistically significant excesses among female food industry workers. Among specific occupations in the food industry, the only significant excess in overall cancer incidence (SIR 5 1.35, CI 5 1.02–1.76) was found in men (but not in women) belonging to ‘‘other occupations in the food industry’’ (Table II). This class covers jobs in the processing of margarine, yeast, cocoa, coffee, spice, macaroni, fish and poultry products and in the refrigeration
personnel. There was an excess of kidney cancer (4.20, 1.69–8.65) among men. There was an excess of lung cancer among female bakers (1.38, 1.01–1.85), but not among male bakers (Table II). The only other significantly elevated SIR in respiratory tract cancers was the one for laryngeal cancer among male grain millers (2.60, 1.05–5.36) (Table III). Among the cancers not related to the respiratory tract, pancreatic, urinary tract, skin melanoma, and leukemias showed elevated SIRs in certain occupations (Table IV). Elevated risks of esophageal and stomach cancer and different types of leukemia among many occupations in the food industry have been reported in several studies. The SIRs of these cancers for all occupations in the food industry are presented in Table IV. We found no statistically significantly elevated SIRs among chocolate and confectionery manufacturers, cannery workers and processed food workers. Discussion Food industry workers as an undivided occupational group have shown an elevated risk of cancer of the oesophagus,11 stomach,12–14 small intestine,15 gall bladder16 and pancreas.16 We only found an excess of pancreas cancer among Finnish male food industry workers. Male food and beverage workers have been found to have an elevated incidence of sinonasal,17 laryngeal16 and lung16 cancer.
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CANCER RISK AMONG FINNISH FOOD INDUSTRY WORKERS TABLE III – OCCUPATIONS IN THE FOOD INDUSTRY, OBSERVED (O) AND EXPECTED (E) NUMBERS OF NASAL AND LARYNGEAL CANCERS, STANDARDIZED INCIDENCE RATIO (SIR) AND ITS 95% CONFIDENCE INTERVAL (CI) IN 1971–95 Nasal cancer Occupation
Grain millers Bakers Chocolate and confectionery manufacturers Brewers, beverage makers and kilnmen Cannery workers Butchers and sausage makers Dairy workers Processed food workers Sugar processing workers Other occupations in the food industry
Laryngeal cancer
Men
Women
O
E
SIR
95% CI
O
E
0 2 0
0.4 0.6 0.1
0 3.41 0
0.00–10.4 0.41–12.3 0.00–53.5
0 0 0
0.0 1.1 0.2
0
0.1
0
0.00–28.9
1
0 0
0.1 0.7
0 0
0.00–36.4 0.00–5.42
1 0 0 0
0.3 0.0 0.1 0.1
3.10 0 0 0
0.08–17.3 0.00–286 0.00–33.0 0.00–35.5
SIR
Men
Women
95% CI
O
E
SIR
95% CI
O
E
SIR
95% CI
0 0 0
0.00–276 0.00–3.24 0.00–23.5
7 4 0
2.7 4.1 0.5
2.60 0.98 0
1.05–5.36 0.27–2.52 0.00–7.48
0 2 0
0.0 1.1 0.2
0 1.79 0
0.00–326 0.22–6.47 0.00–24.9
0.1
9.23
0.23–51.4
2
0.9
2.13
0.26–7.69
1
0.1
9.62
0.24–53.6
0 1
0.1 0.2
0 4.77
0.00–31.4 0.12–26.6
1 3
0.7 4.8
1.35 0.63
0.03–7.53 0.13–1.83
0 0
0.1 0.2
0 0
0.00–29.1 0.00–17.1
0 0 0 1
0.5 0.1 0.0 0.1
0.00–7.85 0.00–32.9 0.00–191 0.40–87.2
3 0 0 0
2.3 0.1 0.8 0.8
1.29 0 0 0
0.27–3.78 0.00–38.4 0.00–4.45 0.00–4.77
0 0 0 0
0.5 0.1 0.0 0.1
0 0 0 0
0.00–7.55 0.00–32.5 0.00–177 0.00–57.5
0 0 0 15.7
These associations were not repeated in our study. Cervical16 and testicular cancer18 has also been found in previous studies, but not in our study. An excess mortality of bladder cancer occurred among food workers in England and Wales, particularly among those employed in the bread and flour confectionary industry or involved in the extraction of animal and vegetable oils and fats.19 We found excesses of kidney cancer among men in the food industry, but not among women. Kidney cancer has not been reported in previous studies. Smoking increases the risk of kidney20 and pancreas20,21 cancers, but smoking among male food industry workers does not markedly differ from economically active men in Finland.22 Asbestos, petroleum products and dry cleaning solvents appear to be associated with kidney cancer,23 and chlorinated hydrocarbon solvents and related compounds, nickel and nickel compounds, chromium and chromium compounds, polycyclic aromatic hydrocarbons, organochlorine insecticides, silica dust and aliphatic and alicyclic hydrocarbon solvents with pancreatic cancer.24 These exposures are not common in the food industry. Working in the food industry has been suggested as a possible risk factor for uveal melanomas,25 Hodgkin’s disease, non-Hodgkin lymphomas and multiple myeloma.26 These hypotheses did not gain support in our study. Excesses of stomach cancer have been found among grain millers.27 An elevated risk for developing pancreatic cancer, non-Hodgkin lymphoma and leukemia was found in flour mills, where pesticides were used more frequently than in other segments of the industry.28 A significant excess of sinonasal cancer has been found among male grain millers in France.29 We found an excess of larynx cancer among male grain millers. An elevated risk for larynx cancer among grain millers has not been reported in previous studies. Bakers have shown an increased risk of lung cancer in Italy.30 A significant excess risk of nasophapharyngeal cancer has been found in China31 and of sinonasal cancer in France.29 Malignant pleural mesotheliomas were found among bakers that have used asbestos-insulated ovens.32 We found an excess of lung cancer among female bakers, which is consistent with the above-mentioned Italian study. We also found an excess of cancer of the urinary tract among male bakers not found in other studies. Our observation on nasal cancer was uninformative (observed 2 cases, expected 1.7). The flours used vary globally. The main flours used in Finland are wheat, rye and oat. Among confectionery makers, an elevated risk for nasopharyngeal and sinonasal cancer has been found.31,33 An excess of oesophageal cancer has been found among Swedish male confectionery makers.11 We did not find any excesses of cancer among the chocolate and confectionery workers in our cohort. Among beverage manufacturing workers, elevated risks for oesophageal11,34, stomach27, pancreas16 and lung cancer16 have been found. We found an excess of pancreatic and soft tissue cancer.
There were only 4 cases of soft tissue cancer vs. 0.8 expected, but our result is similar to the observation from the other Nordic countries and may indicate a real association. The category of cannery workers includes jobs in which meat, fish, fruits and other materials are prepared for preservation and preserved by sterilization, deep freezing or other methods. An excess of sinonasal cancer has been found among men employed as food preservers17 and in women employed in canning and preserving fruit and vegetables.33 An excess of nonlymphatic leukemia was found among cannery workers in the USA.35 We did not find any elevated cancer risks among the cannery workers in our study. Among butchers and meat workers, an excess of cancers of the oral cavity and pharynx,36 oesophagus,11 stomach13,36 and larynx36,37 have been found. Working in poultry slaughtering plants increased the risk of cancer of the oesophagus and liver and tumors of the haematopoietic lymphatic system in USA,38 and an excess of nonlymphatic leukemia was found among meat cutters in the USA.35 Some studies have shown an excess of lung cancer among meat workers,36,39 whereas others have not.40,41 The lung cancer risk is associated most strongly with animal slaughtering and exposure to freshly slaughtered meat or to biological material contained in blood and animal faecal matter, according to a recent literature review.42 We found an excess of skin melanoma among men and leukemia (non-CLL) among women. An excess of skin melanoma has not been found in other studies. The main animals slaughtered in Finland are cows, pigs, poultry and reindeer. An excess of non-Hodgkin lymphomas was found among dairy workers in Sweden.43 We did not find an excess in non-Hodgkin lymphomas, but we found an elevated risk of non-CLL. There is no significant benzene or ionizing radiation exposure in the Finnish dairy industry, which would explain this association. An excess of cancers of the urinary tract among men were found in our study among sugar refinery workers, but none among women were found in our study. Men also had a significant excess of CLL, but the number of cases was only 3. These kinds of findings have not been reported in previous studies. We also found an excess of kidney cancer in the group of other occupations in the food industry. The significance of this finding is difficult to evaluate due to the heterogeneity of this group. The major inhalatory exposures in the food industry are flour and plant dust (Table I). About 11,000 (40%) Finns working in the food industry were exposed to flour dust in 1960–84, according to FINJEM. Detergents are also widely used, but the exposure is mainly dermal, and the related health effects are eczemas. Bacteria and moulds are a significant exposure in certain occupations in the food industry. Some of them are intentionally cultivated and are
2570
LAAKKONEN ET AL.
TABLE IV – OBSERVED (O) AND EXPECTED (E) NUMBERS OF OESOPHAGUS CANCER, STOMACH CANCER, CHRONIC LYMPHATIC LEUKAEMIA (CLL), AND OTHER LEUKAEMIA (NON-CLL), STANDARDIZED INCIDENCE RATIO (SIR) AND ITS 95% CONFIDENCE INTERVAL (CI) FOR ALL OCCUPATIONS IN THE FOOD INDUSTRY AND FOR THOSE CANCER SITES WITH A 95% CONFIDENCE INTERVAL OF THE STANDARDIZED INCIDENCE RATIO GREATER THAN 1.0 WITH THE ASSOCIATED OCCUPATIONS IN 1971–95 Occupation
Grain millers
Bakers
Chocolate and confectionery manufacturers Brewers, beverage makers and kilnmen
Cannery workers
Butchers and sausage makers
Dairy workers
Processed food workers
Sugar processing workers
Other occupations in the food industry
Men
Site
Oesophagus Stomach Non-CLL CLL Oesophagus Stomach Bladder, ureter and urethra Non-CLL CLL Oesophagus Stomach Non-CLL CLL Oesophagus Stomach Pancreas Soft tissue Non-CLL CLL Oesophagus Stomach Non-CLL CLL Oesophagus Stomach Skin melanoma Non-CLL CLL Oesophagus Stomach Non-CLL CLL Oesophagus Stomach Non-CLL CLL Oesophagus Stomach Bladder, ureter and urethra Non-CLL CLL Oesophagus Stomach Kidney Non-CLL CLL
Women
O
E
SIR
95% CI
O
E
SIR
95% CI
0 16 3 2 5 11 22
1.8 11.8 2.1 1.5 2.8 17.6 12.8
0 1.36 1.44 1.30 1.79 0.63 1.72
0.00–2.01 0.78–2.21 0.30–4.20 0.16–4.69 0.58–4.17 0.31–1.12 1.08–2.61
0 2 0 0 11 35 8
0.1 0.5 0.1 0.1 7.8 40.7 12.2
0 4.29 0 0 1.41 0.86 0.66
0.00–42.1 0.52–15.5 0.00–31.0 0.00–62.9 0.70–2.52 0.60–1.20 0.28–1.29
1 1 2 4 0 1 2 7 8 1 0 1 0 4 0 0 5 21 13 5 0 3 9 3 0 0 0 0 0 0 1 7
3.5 2.2 0.3 2.0 0.4 0.2 0.6 4.0 1.9 0.3 0.7 0.5 0.5 3.1 0.6 0.4 3.2 19.3 6.8 3.9 2.3 1.5 9.4 1.8 1.1 0.1 0.4 0.1 0.1 0.6 3.4 2.5
0.29 0.45 6.30 2.05 0 4.19 3.10 1.75 4.12 3.02 0 2.00 0 1.29 0 0 1.58 1.09 1.91 1.29 0 1.97 0.96 1.65 0 0 0 0 0 0 0.29 2.82
0.01–1.60 0.01–2.49 0.76–22.8 0.56–5.26 0.00–9.50 0.11–23.3 0.38–11.2 0.70–3.61 1.78–8.12 0.08–16.9 0.00–5.00 0.05–11.2 0.00–7.36 0.35–3.31 0.00–6.32 0.00–9.59 0.51–3.69 0.67–1.66 1.02–3.27 0.42–3.01 0.00–1.57 0.41–5.75 0.44–1.82 0.34–4.82 0.00–3.22 0.00–65.4 0.00–9.83 0.00–52.1 0.00–79.0 0.00–6.72 0.01–1.63 1.13–5.81
7 5 2 4 2 0 1 4 5 3 0 1 0 6 0 0 0 12 2 7 0 2 21 10 3 1 2 1 0 0 0 0
10.7 4.9 1.1 5.6 1.5 0.7 0.7 3.8 2.5 0.5 1.0 0.5 0.9 4.4 1.1 0.5 1.5 7.6 3.2 2.0 0.9 2.9 16.7 4.8 1.9 0.8 4.1 1.1 0.5 0.1 0.7 0.2
0.65 1.03 1.91 0.71 1.35 0 1.41 1.04 2.04 6.14 0 2.24 0 1.37 0 0 0 1.57 0.63 3.43 0 0.69 1.26 2.08 1.58 1.28 0.49 0.92 0 0 0 0
0.26–1.34 0.33–2.40 0.23–6.89 0.19–1.82 0.16–4.86 0.00–5.65 0.04–7.85 0.28–2.67 0.66–4.76 1.27–18.0 0.00–3.57 0.06–12.5 0.00–4.20 0.50–2.99 0.00–3.25 0.00–7.02 0.00–2.55 0.81–2.74 0.08–2.29 1.38–7.07 0.00–4.14 0.08–2.50 0.78–1.92 1.00–3.82 0.33–4.63 0.03–7.12 0.06–1.78 0.02–5.14 0.00–7.77 0.00–28.4 0.00–5.34 0.00–17.6
1 3 1 5 7 2 1
0.6 0.4 0.5 3.1 1.7 0.6 0.4
1.61 7.14 2.00 1.60 4.20 3.41 2.56
0.04–8.99 1.47–20.9 0.05–11.2 0.52–3.73 1.69–8.65 0.41–12.3 0.06–14.2
0 0 0 2 3 1 0
0.2 0.1 0.5 2.3 1.3 0.6 0.3
0 0 0 0.86 2.38 1.66 0
0.00–19.9 0.00–45.7 0.00–8.02 0.10–3.09 0.49–6.95 0.04–9.24 0.00–13.4
necessary in the preparation process, while others are a disadvantage. The inhalation of fungal spores may cause cancer.44 Some mycotoxins that are potential exposures in the food industry are carcinogenic. Employees may be exposed to aflatoxin B (IARC group 1: carcinogenic to humans) in animal feed production45 and ochratoxin A (IARC group 2B: possibly carcinogenic to humans) in coffee, cocoa and spice processing.46 The role of endotoxins as carcinogens is unknown. According to one study endotoxins might even reduce lung cancer rates in some occupational groups.47 The socioeconomic status of all occupations in the Finnish food industry is skilled blue-collar. Our results were adjusted for social class. Social class correlates well with certain lifestyle habits, such as smoking in men; and the adjustment for social class can therefore be considered as satisfactory proxy for the adjustment for some cancer-related co-factors.48,49 We had lifestyle habit data for the food industry workers from surveys. About 40% of men and 20% of women smoked daily among the occupations studied in the 1970s. This is approximately the same as in the Finnish employed population during the same period.22
Bakers, dairy workers, and butchers and sausage makers were the largest occupations in 1960–84 (Table I). The number of workers employed in the Finnish food industry has decreased by one third from those days, but the food industry still belongs to one of the largest employers in Finland. Cannery workers have replaced dairy workers as one of the major occupations. The proportions of different occupations in the Finnish food industry have otherwise remained about the same. According to FINJEM, the major chemical exposures also continue to be about the same. The occupation at one point in time may not correspond to the lifelong occupational history of a person. The occupational stability of Finnish food industry workers is high.50 The use of group level cross-sectional exposure estimates adds some misclassification and therefore dilutes the RR estimates towards unity, but because of the large size of our study even these diluted risk estimates remain significant and show possible patterns of risk increase with increasing exposure.5 Different studies on cancer risk in the food industry tend to pick up different cancer sites, and the increased cancer risks are rarely
CANCER RISK AMONG FINNISH FOOD INDUSTRY WORKERS
found consistently in many data sets. This suggests that the excesses reported may be partly chance findings attributable to multiple testing, or due to lifestyle factors that may vary widely by country. There were no statistically significant elevated site-specific cancer risks among both genders in any occupation in our cohort. We conclude that occupational exposure is thus unlikely to be a major risk
2571
factor of cancer in typical food industry occupations in Finland. We found some weak support for the previous findings, according to which exposure to flour and plant dust (grain dust) might elevate the risk of respiratory tract cancers. The occupation-specific excesses should be interpreted with caution, because the lifestyle related confounding factors may affect these results.
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