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. 2006 Apr 6;63(11):726–733. doi: 10.1136/oem.2005.025825

Occupational exposure to eight organic dusts and respiratory cancer among Finns

A Laakkonen 1,2, P Kyyrönen 1,2, T Kauppinen 1,2, E I Pukkala 1,2
PMCID: PMC2077994  PMID: 16601013

Abstract

Background

There is inconclusive evidence concerning cancer risks of organic dusts.

Aim

The carcinogenic exposures are mainly inhalatory and the authors therefore studied associations between occupational exposure to eight different organic dusts and respiratory cancers in Finland.

Methods

The authors followed up a cohort of all economically active Finns born between 1906 and 1945 for 30 million person‐years during 1971–95. Incident cases of nasal, laryngeal, and lung cancer and mesotheliomas were identified through a record linkage with the Finnish Cancer Registry. Occupations from the population census in 1970 were converted to exposures to eight organic dusts with a job‐exposure matrix (FINJEM). Cumulative exposure (CE) was calculated as a product of prevalence, level, and estimated duration of exposure. Standardised incidence ratios (SIR) and 95% confidence intervals (CI) adjusted for age, period, and social class were calculated for each organic dust using the economically active population as the reference.

Results

A total of 20 426 incident cases of respiratory cancer were observed. Slightly increased risk was observed among men exposed to wood dust for nasal cancer (SIR 1.42, 95% CI 0.79 to 2.44). For laryngeal cancer, men exposed to plant dust (mainly grain millers) had a raised SIR in the high exposure class (SIR 3.55, 95% CI 1.30 to 7.72). Men exposed to wood dust had a raised SIR for lung cancer, but only in the low exposure class (SIR 1.11, 95% CI 1.04 to 1.18). Women exposed to wood dust showed an increased SIR for mesotheliomas in the low exposure class (SIR 4.57, 95% CI 1.25 to 11.7) and some excess in the medium exposure category.

Conclusions

Exposure to organic dusts is unlikely to be a major risk factor of respiratory cancer. Even exposure to wood dust which is a major exposure in Finland seems to have minor effect for nasal cancer. The authors found suggestive evidence that exposure to grain dust may increase the risk of laryngeal cancer, and some support to the hypothesis that exposure to textile dust, and to plant and animal dust (agricultural dusts) may decrease the risk of lung cancer.

Keywords: cancer, organic dust, occupational exposure, job‐exposure matrix

Organic dusts are established causes of respiratory tract irritation and allergy1 but their significance as occupational carcinogens is mostly unknown. Exposure to organic dusts occurs in many industries and occupations, and the number of people exposed is high. The International Agency for Research on Cancer (IARC) has published monographs on cancer risks in the textile, leather, and wood industries where exposure to organic dusts is frequent.2,3,4 Textile manufacturing industry has been classified as possibly carcinogenic to humans (group 2B) by the IARC. There is limited evidence that the risk of cancer of the nasal cavity among weavers is increased. There is no evidence to suggest an association between work in the leather industry and respiratory cancer according to the IARC monograph. Wood dust has been classified as carcinogenic to humans (group 1) by the IARC, mainly based on evidence on nasal cancer among workers predominantly exposed to hardwood dusts. Excesses of lung cancer have been reported among bakers and tailors.5 An increased risk of lung cancer and pleural mesothelioma has been found in some studies also among furniture workers6 and in the pulp and paper industry.7 An increased risk of lung cancer has been found among cardboard workers.8 Finnish sawmill workers have been found to have an excess of pharyngeal cancer.9 However, there are also studies suggesting no excess risk of respiratory cancer among woodworkers,10,11 pulp mill workers,12 or paper mill workers.13

Because of inconclusive evidence concerning cancer risks of organic dusts, the objective of the present study was to assess associations between occupational exposure to eight different organic dusts and four types of respiratory cancer in Finland.

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.14 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 Labour Organization (ILO).15 The socioeconomic status (SES) for each subject was based on the subject's own, or in some cases the spouse's, occupation. In our analyses, the SESs were categorised as farmers, higher white‐collar, clerical, skilled blue‐collar, and unskilled workers. FINJEM also includes alcohol (g/week) and smoking data (daily smokers) by occupation. These data were obtained from annual surveys carried out on the health behaviour of the Finnish adult population by the Finnish National Public Health Institute during 1978–91.16 For rare occupations in which the number of respondents in the surveys was below 20, we estimated the values by using data of larger proxy occupations. The smoking index indicated the effect of a 10% increase in the daily smoking prevalence of an occupation and alcohol index the effect of one additional drink/day. 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 pathological, cytological, and haematological laboratories in the country must notify the FCR of all cancer cases that come to their attention. In addition, Statistics Finland annually provides a computerised file on death certificates in which cancer is mentioned. The FCR coverage is virtually complete and the data accuracy high.17,18

In this study the incident cases of respiratory cancers diagnosed during 1971–95 among people 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 computerised record linkages. The researchers had only data in which no individuals could be recognised.

Occupational exposures of the cohort were assessed by using FINJEM,19,20 which covers major occupational exposures in Finland since 1945 by occupation and calendar time. Exposure is characterised 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 estimates for 1960–84 were used. The number of workers potentially exposed to organic dusts in Finland is estimated to be about 200 000 according to FINJEM, which is 8% of the employed population. The main organic dusts are plant dust, animal dust, wood dust, and textile dust. The occupations with organic dust exposure in Finland according to FINJEM are presented in table 1.

Table 1 Occupations with exposure to eight organic dusts, proportion of exposed persons (P) in %, and average exposure level (L) in 1960–84 according to FINJEM.

Code Occupation Exposure (unit mg/m3)
Wood dust Pulp or paper dust Flour dust Plant dust Textile dust Leather dust Animal dust Synthetic polymer dust
P L P L P L P L P L P L P L P L
024 Veterinarians 100 0.05
052 Secondary school rectors, teachers, and instructors 1 0.25
300 Farmers, silviculturists, horticulturists 89 0.51 74 0.02
305 Livestock breeders 29 0.60 100 0.02
306 Fur farmers 100 0.38
310 Farm workers 80 0.66 62 0.03
312 Fur farm workers 100 0.38
319 Occupations in agriculture, horticulture, and animal husbandry, nec 63 0.05
600 Fibre processors 44 3.13 11 1.00 22 0.20
601 Spinning machine operators 45 1.57 100 1.00 5 1.00
602 Wearing machine operators 61 0.71 26 0.40
603 Textile machine setter operators 6 1.60 100 0.80
604 Knitting machine operators 100 0.7
605 Textile finishers, dyers 29 0.50 9 0.10
606 Textile inspectors 100 0.50
609 Occupations in textiles, nec 19 0.30 19 0.35
610 Tailors, salon seamstresses 100 0.15
611 Furriers 100 0.70
612 Milliners and hatmakers 73 0.20
613 Upholsterers 65 0.05 43 0.08
614 Patternmakers and cutters (also leather garments and gloves) 76 0.70 4 0.20 22 0.40
615 Industrial sewers etc (also leather garments and gloves) 77 0.60 4 0.60 19 0.40
619 Cutting, sewing, and upholstering occupations, nec 58 0.70 29 0.50
621 Leather cutters for footwear 74 0.70
623 Lasters and sole fitters, etc 17 0.15
625 Leather sewers, etc 18 0.50
670 Timbermen 56 0.68
671 Sawyers 100 0.75
672 Plywood and fibreboard workers 66 1.02
673 Construction carpenters 100 0.08
674 Wooden boatbuilders, coach‐body builders, etc 90 0.20
675 Bench carpenters 100 1.14
676 Cabinetmakers and joiners etc 100 1.00
677 Woodworking machine operators, etc 100 2.50
678 Wooden surface finishers 80 0.10
679 Woodworking occupations, nec 100 0.10
680 Painters, lacquerers, and floor layers 18 2.98
703 Bookbinders 100 0.10
720 Grain millers 45 17.25 67 3.22
721 Bakers 87 3.20 9 1.00
722 Chocolate and confectionery manufacturers 4 1.00
723 Brewers, beverage makers, and kilnmen 3 5.00
725 Butchers and sausage makers 2 10.00
727 Processed food workers 16 5.00
729 Occupations in the food industry, nec 12 10.00 33 1.00
735 Paper and cardboard mill workers 47 0.80
740 Tobacco industry workers 82 0.38
751 Rubber products workers 10 1.00
752 Plastic product workers 2 0.92
753 Tanners, fellmongers, and pelt dressers 23 1.00
757 Paper products workers 49 0.50
760 Packers and labellers etc 5 0.50 5 1.19 1 3.57 5 0.60
811 Cooks etc 4 0.25
831 Charworkers 1 4.00 1 0.50 1 8.24
850 Laundry workers 6 0.20
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The respiratory cancers studied were nasal cancer (ICD10 C30, C31), laryngeal cancer (C32), lung cancer (C34), and mesotheliomas (C45). The observed and expected numbers of respiratory cancer cases for every organic dust class were calculated for each five year calendar period, five year birth cohort, gender, and SES. The expected number in each stratum was calculated by multiplying the number of person‐years with the cancer incidence rate of the entire economically active Finnish population in the respective stratum. The standardised 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 with adjustments for confounding factors. Poisson regression analysis of the stratum specific observed numbers of cases and person‐years at risk was used in internal comparison to further study dose‐response patterns and the effects of confounding factors. We calculated agent specific cumulative exposure (CE) estimates to every five year birth cohort (1906–10, …, 1941–45) and every five year calendar period of observation (1971–75, ..., 1991–95). Exposure for each birth cohort was assumed to start in the year when the average age of the birth cohort was 20 and to end in the mid‐year of the observation period, or at 65 years of age, whichever came first. If the exposure took place before 1960, we used the FINJEM estimates for the period 1945–59; otherwise the estimates for the period 1960–84 were applied in the analyses. A lag period was incorporated into the CE by omitting exposure years before the mid‐point of the observation period. A 20 year lag period was applied. For instance, when studying cancer risk in 1971–75, only exposures until 1953 were taken into account. The exposure class limits for organic dusts in FINJEM were set a priori so that the “high” CE class was rather small, and included as far as possible long term workers with high exposure. The rest of the potentially exposed subjects were divided into “medium” and “low” CE classes.

Results

Men exposed to wood dust had an increased SIR for nasal cancer (table 2); the SIR for all exposed men was 1.42 (95% CI 0.79 to 2.44). The number of cases among exposed women was only two. The other organic dusts did not show significant differences from the entire economically active Finnish population for nasal cancer, although SIRs related to exposure to flour dust tended to be above 1.0.

Table 2 Standardised incidence ratio (SIR) of nasal and laryngeal cancers in 1971–95 by gender and cumulative exposure (CE) to eight organic dusts among economically active Finns born 1906–45.

Agent CE class Nasal cancer Laryngeal cancer
Men Women Men Women
O SIR 95% CI O SIR 95% CI O SIR 95% CI O SIR 95% CI
Wood dust None (0) 259 0.96 0.85–1.09 118 1.00 0.83–1.20 1965 1.02 0.97–1.06 128 0.99 0.83–1.18
Low (<3 mg/m3‐year) 15 1.57 0.88–2.58 1 1.74 0.04–9.69 76 1.06 0.83–1.32 1 1.22 0.03–6.80
Medium (3–50 mg/m3‐year) 17 1.29 0.75–2.07 1 0.80 0.02–4.43 77 0.71 0.56–0.88 3 2.09 0.43–6.11
High (>50 mg/m3‐year) 1 1.24 0.03–6.89 0 0.00 0.00–9.70 1 0.13 0.00–0.74 0 0.00 0.00–7.79
Pulp or paper dust None (0) 290 1.00 0.89–1.12 118 1.00 0.83–1.20 2097 1.00 0.96–1.04 130 1.00 0.84–1.19
Low (<10 mg/m3‐year) 1 0.70 0.02–3.88 1 1.42 0.04–7.89 12 1.32 0.68–2.31 2 1.97 0.24–7.11
Medium (10–15 mg/m3‐year) 1 1.03 0.03–5.76 1 0.95 0.02–5.27 10 1.15 0.55–2.12 0 0.00 0.00–3.22
High (>15 mg/m3‐year) 0 0.00 0.00–131 0 0.00 0.00–66.4 0 0.00 0.00–11.4 0 0.00 0.00–134
Flour dust None (0) 290 1.00 0.89–1.12 102 0.96 0.78–1.17 2102 1.00 0.96–1.04 120 1.05 0.87–1.26
Low (<5 mg/m3‐year) 0 0.00 0.00–5.65 15 1.22 0.69–2.02 3 0.68 0.14–1.99 10 0.62 0.30–1.13
Medium (5–50 mg/m3‐year) 0 0.00 0.00–6.62 3 3.96 0.82–11.6 4 0.96 0.26–2.46 0 0.00 0.00–5.63
High (>50 mg/m3‐year) 2 2.45 0.30–8.83 0 0.00 0.00–3.98 10 1.51 0.72–2.78 2 1.81 0.22–6.54
Plant dust None (0) 233 1.02 0.89–1.16 80 0.99 0.79–1.23 1677 1.01 0.96–1.06 99 1.05 0.86–1.28
Low (<10 mg/m3‐year) 27 0.85 0.56–1.23 23 1.06 0.67–1.59 219 0.96 0.84–1.10 18 0.77 0.46–1.22
Medium (10–40 mg/m3‐year) 32 1.01 0.69–1.43 17 0.97 0.57–1.55 217 0.95 0.83–1.09 15 1.02 0.57–1.68
High (>40 mg/m3‐year) 0 0.00 0.00–18.7 0 0.00 0.00–49.9 6 3.55 1.30–7.72 0 0.00 0.00–96.8
Textile dust None (0) 288 1.00 0.88–1.12 117 1.04 0.86–1.25 2099 1.00 0.96–1.04 122 0.99 0.82–1.18
Low (<5 mg/m3‐year) 2 1.40 0.17–5.07 0 0.00 0.00–1.28 8 0.74 0.32–1.46 4 1.15 0.31–2.94
Medium (5–20 mg/m3‐year) 1 1.19 0.03–6.63 2 0.49 0.06–1.77 7 1.09 0.44–2.24 3 0.65 0.13–1.90
High (>20 mg/m3‐year) 1 3.34 0.08–18.6 1 1.23 0.03–6.87 5 1.83 0.59–4.26 3 3.71 0.77–10.8
Leather dust None (0) 291 1.00 0.89–1.12 120 1.00 0.83–1.20 2112 1.00 0.96–1.04 132 1.01 0.84–1.19
Low (<5 mg/m3‐year) 1 2.01 0.05–11.2 0 0.00 0.00–7.83 5 1.30 0.42–3.04 0 0.00 0.00–6.61
Medium (5–20 mg/m3‐year) 0 0.00 0.00–18.6 0 0.00 0.00–31.9 2 1.22 0.15–4.42 0 0.00 0.00–29.8
High (>50 mg/m3‐year) 0 0.00 0.00–1080 0 0.00 0.00–728 0 0.00 0.00–94.0 0 0.00 0.00–1460
Animal dust None (0) 241 1.01 0.88–1.14 96 1.01 0.82–1.23 1760 1.01 0.97–1.06 112 1.00 0.82–1.20
Low (<0.5 mg/m3‐year) 36 0.92 0.64–1.27 8 0.81 0.35–1.59 300 0.95 0.85–1.07 8 1.04 0.45–2.06
Medium (0.5–1.5 mg/m3‐year) 14 1.07 0.58–1.79 16 1.10 0.63–1.79 53 0.83 0.62–1.08 12 1.03 0.53–1.80
High (>1.5 mg/m3‐year) 1 2.22 0.06–12.4 0 0.00 0.00–22.7 6 1.90 0.70–4.14 0 0.00 0.00–24.0
Synthetic polymer dust None (0) 291 1.00 0.89–1.12 118 1.02 0.85–1.22 2105 1.00 0.96–1.04 129 1.02 0.85–1.21
Low (<5 mg/m3‐year) 1 0.55 0.01–3.08 2 0.45 0.05–1.61 14 1.03 0.56–1.72 3 0.61 0.13–1.79
Medium (5–20 mg/m3‐year) 0 0.00 0.00 0 0.00 0.00 0 0.00 0.00 0 0.00 0.00
High (>20 mg/m3‐year) 0 0.00 0.00 0 0.00 0.00 0 0.00 0.00 0 0.00 0.00
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O, observed number of cases; CI, confidenceinterval; SIRs adjusted for age and social class, exposure lag period 20 years.

For laryngeal cancer, men exposed to plant dust had a statistically elevated SIR in the highest exposure class (SIR 3.55, CI 1.30 to 7.72) (table 2). Women did not show elevated SIRs for plant dust and laryngeal cancer. The most exposed men were mainly grain millers. Flour dust suggested an exposure response trend among men. Textile dust also showed minor suggestions of a similar trend.

For lung cancer, men exposed to wood dust had a significantly elevated SIR for lung cancer, but only in the low exposure class (SIR 1.11, CI 1.04 to 1.18) (table 3). The excess cases were mainly squamous cell carcinomas (SIR 1.14, CI 1.06 to 1.22). No other organic dust showed increased SIRs for lung cancer, but numerous worker groups with dust exposure had lung cancer incidence significantly below the national average (table 3).

Table 3 Standardised incidence ratio (SIR) of lung cancer and mesotheliomas in 1971–95 by gender and cumulative exposure (CE) to eight organic dusts among economically active Finns born 1906–45.

Agent CE class Lung cancer Mesotheliomas
Men Women Men Women
O SIR 95% CI O SIR 95% CI O SIR 95% CI O SIR 95% CI
Wood dust None (0) 27309 1.00 0.98–1.01 3446 1.00 0.97–1.03 408 1.01 0.91–1.11 135 0.97 0.81–1.14
Low (<3 mg/m3‐year) 936 1.11 1.04–1.18 21 0.92 0.57–1.41 12 0.83 0.43–1.46 4 4.57 1.25–11.7
Medium (3–50 mg/m3‐year) 1784 1.02 0.97–1.06 48 1.03 0.76–1.37 28 0.98 0.65–1.41 4 2.10 0.57–5.37
High (>50 mg/m3‐year) 108 0.85 0.70–1.02 12 0.95 0.49–1.66 2 1.06 0.13–3.84 0 0.00 0.00–7.67
Pulp or paper dust None (0) 29933 1.00 0.99–1.01 3477 1.00 0.97–1.04 449 1.01 0.92–1.11 139 0.99 0.83–1.17
Low (<10 mg/m3‐year) 102 0.82 0.67–1.00 25 0.97 0.62–1.43 0 0.00 0.00–1.42 3 2.97 0.61–8.67
Medium (10–15 mg/m3‐year) 100 0.82 0.66–0.99 23 0.71 0.45–1.07 1 0.43 0.01–2.38 1 0.80 0.02–4.44
High (>15 mg/m3‐year) 2 1.22 0.15–4.42 2 1.08 0.13–3.89 0 0.00 0.00–31.8 0 0.00 0.00–65.2
Flour dust None (0) 29944 1.00 0.99–1.01 3116 1.00 0.97–1.04 448 1.00 0.91–1.10 132 1.03 0.87–1.23
Low (<5 mg/m3‐year) 54 0.86 0.65–1.13 350 0.97 0.87–1.07 0 0.00 0.00–3.13 10 0.78 0.37–1.43
Medium (5–50 mg/m3‐year) 50 0.89 0.66–1.18 17 0.68 0.40–1.10 1 0.83 0.02–4.60 0 0.00 0.00–3.55
High (>50 mg/m3‐year) 89 0.95 0.77–1.18 44 1.20 0.87–1.61 1 0.63 0.02–3.50 1 0.66 0.02–3.66
Plant dust None (0) 23211 1.03 1.02–1.05 2684 1.00 0.97–1.04 409 1.01 0.91–1.11 106 1.00 0.82–1.21
Low (<10 mg/m3‐year) 2555 0.86 0.82–0.89 495 0.99 0.90–1.08 20 0.93 0.57–1.43 20 0.90 0.55–1.39
Medium (10–40 mg/m3‐year) 4340 0.93 0.90–0.96 347 0.98 0.88–1.09 21 0.98 0.60–1.49 17 1.16 0.68–1.86
High (>40 mg/m3‐year) 31 1.06 0.72–1.51 1 0.55 0.01–3.05 0 0.00 0.00–8.50 0 0.00 0.00–50.1
Textile dust None (0) 29867 1.00 0.99–1.01 3288 1.01 0.98–1.05 449 1.01 0.92–1.11 131 0.99 0.83–1.18
Low (<5 mg/m3‐year) 162 1.08 0.92–1.26 95 0.99 0.80–1.21 0 0.00 0.00–1.43 4 1.15 0.31–2.94
Medium (5–20 mg/m3‐year) 82 0.87 0.69–1.08 125 0.79 0.66–0.95 1 0.61 0.02–3.42 4 0.62 0.17–1.59
High (>20 mg/m3‐year) 26 0.66 0.43–0.97 19 0.60 0.36–0.94 0 0.00 0.00–5.24 4 3.18 0.87–8.15
Leather dust None (0) 30069 1.00 0.99–1.01 3511 1.00 0.97–1.04 450 1.00 0.91–1.10 143 1.01 0.85–1.19
Low (<5 mg/m3‐year) 47 0.85 0.62–1.13 12 0.66 0.34–1.15 0 0.00 0.00–4.04 0 0.00 0.00–5.14
Medium (5–20 mg/m3‐year) 20 0.88 0.54–1.36 4 0.90 0.24–2.30 0 0.00 0.00–8.58 0 0.00 0.00–19.4
High (>20 mg/m3‐year) 1 1.00 0.03–5.55 0 0.00 0.00–28.1 0 0.00 0.00–263 0 0.00 0.00–728
Animal dust None (0) 24237 1.03 1.01–1.04 3105 1.01 0.97–1.05 420 1.00 0.91–1.10 122 1.01 0.84–1.20
Low (<0.5 mg/m3‐year) 4519 0.89 0.87–0.92 136 0.95 0.79–1.12 22 0.98 0.61–1.49 6 0.63 0.23–1.37
Medium (0.5–1.5 mg/m3‐year) 1321 0.92 0.87–0.97 284 0.93 0.83–1.05 8 0.99 0.43–1.96 15 1.21 0.68–2.00
High (>1.5 mg/m3‐year) 60 1.22 0.93–1.57 2 0.46 0.06–1.65 0 0.00 0.00–10.2 0 0.00 0.00–18.5
Synthetic polymer dust None (0) 29877 1.00 0.99–1.01 3392 1.01 0.98–1.04 448 1.00 0.91–1.10 138 1.01 0.85–1.20
Low (<5 mg/m3‐year) 204 0.94 0.82–1.08 135 0.81 0.68–0.96 2 0.54 0.07–1.96 5 0.75 0.24–1.75
Medium (5–20 mg/m3‐year) 46 0.68 0.49–0.90 0 0.00 0.00 0 0.00 0.00 0 0.00 0.00
High (>20 mg/m3‐year) 10 1.23 0.59–2.26 0 0.00 0.00 0 0.00 0.00 0 0.00 0.00
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O, observed number of cases; CI, confidence interval; SIRs adjusted for age and social class, exposure lag period 20 years.

Women exposed to wood dust showed a significantly increased SIR for mesotheliomas in the low exposure class (SIR 4.57, CI 1.25–11.7) and also some excess in the middle exposure category (table 3). The total number of cancer cases was eight. The cases were saw mill workers, plywood and wooden board makers, bench carpenters, cabinetmakers and joiners, and woodworking machine operators.

We analysed further some of our suggestive findings by Poisson regression modelling. The significance of plant dust exposure as a risk factor for laryngeal cancer remained in the high exposure class in a Poisson regression analysis where smoking and alcohol exposure was added to the model (table 4).

Table 4 Relative risk (RR) and confidence interval (CI) of laryngeal cancer by cumulative exposure (CE) to plant dust, smoking and alcohol consumption among Finns in 1971–95 adjusted by each other, age, social class and period, lag time 10 years.

Agent/confounder CE class Men Women
RR 95% CI RR 95% CI
Plant dust High (>40 mg/m3‐year) 2.89 1.50–5.57 0 0
Medium (10–40 mg/m3‐year) 0.91 0.72–1.14 0.86 0.23–3.16
Low (<10 mg/m3‐year) 1.03 0.82–1.30 0.65 0.36–1.21
None (reference) 1.00 (reference) 1.00 (reference)
Smoking index Effect of 10% increase in daily smoking prevalence of an occupation 1.12 1.04–1.21 1.45 1.03–2.05
Alcohol index Effect of one additional drink/day 1.31 1.06–1.61 1.65 0.25–10.8
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Varying the lag time from 10 to 20 years or the middle/high cumulative exposure value from 30 mg/m3/year to 40 mg/m3/year did not change the values significantly. The risk was not increased in the lower exposure classes among either men or women. Farmers had a significantly reduced risk of laryngeal cancer.

We also performed a Poisson regression analysis for lung cancer and exposure to plant dust, asbestos, quartz dust, and smoking for methodology control reasons. Increased risks for lung cancer and asbestos and quartz dust exposure and smoking were found as expected but not for plant dust (table 5).

Table 5 Relative risk (RR) and confidence interval (CI) of lung cancer by cumulative exposure (CE) to plant dust, asbestos, quartz dust, and smoking among Finns in 1971–95 adjusted by each other, age, social class, and period, lag time 10 years.

Agent/confounder CE class Men Women
RR 95% CI RR 95% CI
Plant dust High (>40 mg/m3‐year) 1.06 0.80–1.40 0.84 0.40–1.77
Medium (10–40 mg/m3‐year) 0.78 0.73–0.83 0.95 0.72–1.26
Low (<10 mg/m3‐year) 0.94 0.88–1.01 1.02 0.91–1.16
None (reference) 1.00 (reference) 1.00 (reference)
Asbestos High (>10 f/cm3‐year) 1.24 1.15–1.34 1.10 0.69–1.75
Medium (2–10 f/cm3‐year) 1.22 1.15–1.29 0.91 0.54–1.54
Low (<2 f/cm3‐year) 1.06 1.00–1.12 0.75 0.46–1.22
None (reference) 1.00 (reference) 1.00 (reference)
Quartz dust High (>10 mg/m3‐year) 1.24 1.09–1.41 1.18 0.78–1.79
Medium (1–10 mg/m3‐year) 0.98 0.92–1.05 1.23 0.85–1.78
Low (<1 mg/m3‐year) 1.04 0.98–1.09 0.96 0.68–1.34
None (reference) 1.00 (reference) 1.00 (reference)
Smoking index Effect of 10% increase in daily smoking prevalence of an occupation 1.18 1.16–1.21 1.39 1.31–1.47
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Discussion

There is comprehensive evidence on wood dust exposure and sinonasal cancer.21,22,23,24,25,26 Exposure to wood dust has been reported to also increase the risk of laryngeal27,28 and lung cancer.29 The risk of laryngeal cancer was not observed in some other studies.30,31 No risks of upper respiratory and lung cancer was found for endemic wood dusts among Finnish woodworkers in a case control study within a cohort.10 A major part of the excesses of lung and pleural mesothelioma among pulp and paper industry workers can be explained by smoking and asbestos exposure, but the role of sulphur compounds, chloride compounds, and wood dust cannot be excluded.7 We found a slight excess of nasal cancer among men exposed to wood dust. The wood dust exposure in Finland is mainly to softwood dust (pine, spruce), which may explain the smaller risk as compared to many other studies.32 A suggestion of an increased risk of lung cancer among men was found in the low exposure class comprising mainly carpenters. However, the excess was small and it may be explained by slightly higher prevalence of smoking among carpenters as compared to all economically active men.

An excess of lung cancer has been associated with paper dust exposure among maintenance workers in paper mills in Sweden.33 There is potential coexposure—for example, to asbestos and welding fumes in the paper industry.34 We did not find any excesses of respiratory cancers among those exposed to paper or pulp dust.

No associations between exposure to flour dust and laryngeal cancers31 or lung cancer29 have been found with the exception of a suggestive finding of lung cancer among bakers.5 We found only suggestions of an increased risk of laryngeal cancer in the high cumulative exposure class, which mainly includes bakers. Smoking and alcohol consumption among male bakers is more common than among the economically active male Finnish population,16 which may confound this result. We did not find excesses of lung cancer among workers exposed to flour dust. The main flours used in Finland are wheat, rye, and oats.

No excesses of respiratory cancers among those exposed to grain dust were found in Canada.29 Farmers have multiple exposures—for example, to plant dust and animal dust. Farmers have significantly less lung cancer than expected.35 The reduced risk of lung cancer may be due to endotoxin exposure, which occurs in dairy farming.36,37 We also found significantly reduced lung cancer SIRs among those exposed to plant dust and animal dust which are predominantly farmers. We found an excess of laryngeal cancer among men in the high cumulative exposure class of plant dust. The majority in the heavily exposed group were grain millers whereas farmers were the majority in lower exposure categories. The significance of high exposure to plant dust exposure as a separate risk factor for laryngeal cancer remained in Poisson regression analysis model where known risk factors of laryngeal cancer smoking and alcohol were added. The main field crops in Finland are wheat, barley, rye, oats, turnip rape, sugar beet, and timothy, and grains are milled wheat, barley, rye, and oats.

Exposure to textile dust may increase the risk of sinonasal cancer according to some studies38,39,40 but not according to others.21 The mortality from lung cancer has been found to be lower than expected among cotton industry workers and it has been assumed that exposure to cotton dust may reduce the risk of lung cancer.41 No significant excess of lung cancer has been found among glass filament textile workers.42 We found only suggestions of an increased risk of laryngeal cancer among men and women in the highest exposure class. The result may be confounded by smoking and alcohol use or it may be a chance finding. We found a significantly decreased risk of lung cancer in the high exposure category, which supports the hypothesis that endotoxins in textile dust may prevent textile workers from contracting lung cancer.41

Exposure to leather dust may increase the risk of cancer of the nose and paranasal sinuses.43,44 Leather dust particles contain numerous chemicals acquired during the process of leather tanning and finishing (chromium salts, vegetable dye extracts, mineral oils), which may contribute to the carcinogenic effect. An association between leather dust from vegetable tanning and lung cancer has been reported in Swedish leather tanneries.45 We did not find any excesses of respiratory cancer among those exposed to leather dust.

Animal dust is not usually considered as a cause of respiratory cancer. However there are some suggestions that animal origin microbe exposures may increase the risk of lung cancer among farmers46 and butchers.47 Previous studies have reported that endotoxin and other microbial products are inherent elements of farm dusts, particularly in cowsheds, where faeces of animals contaminate organic dusts on which bacteria and fungi adhere and grow.48,49 The job title “farmer” is a crude proxy for exposure to farm dust containing endotoxin‐like substances. A reduced risk of lung cancer has been found among dairy farmers but not among crop/orchard farmers.50,51 Fur farmers are exposed to higher levels of animal dust but lower levels of endotoxins compared to dairy farmers.49,52 We did not find any excess of respiratory cancer among workers exposed to animal dust. Farmers, many of whom are exposed to animal dust, had a significantly low incidence of lung cancer. The heterogeneity of the jobs with animal dust exposure probably explains why lung cancer SIR does not decrease with increasing level of “animal dust”.

Painters (and spray painters in particular) may be exposed to synthetic polymers in paints (polyurethane, epoxy‐ and polyacrylic compounds, etc). These synthetic polymers are not suspected to cause cancers of the respiratory tract according to an IARC monograph.53 We did not find any excesses of respiratory cancer among those exposed to synthetic polymer dust.

To date there is no paradigm providing a base from which the protective effects afforded by an exposure can be confirmed. In a case control study nested in a cohort of Italian farmers, there was evidence for an exposure dependent reduction of lung cancer risk in farmers who ceased working on dairy farms less than 15 years previously.36 Thus protection afforded by exposure to endotoxin‐containing organic dust diminishes over time after removal from that exposure.36 We analysed our animal dust exposure and lung cancer data without lagging exposure and setting the follow up time to 15 years. This did not change the results.

The use of FINJEM in epidemiology has been evaluated in several studies and it has been found accurate enough to reveal established occupational cancer risks.20,54 We used cross sectional 1970 census data. FINJEM converts occupation to exposure data. The occupation at one point in time may not correspond to the lifelong occupational history of a person, although the occupational stability in the occupations with organic dust exposure is high.55 The use of 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 are likely to remain significant and show possible patterns of risk increase with increasing exposure.20,56 Multiple comparisons were made in this study, and therefore some of the findings are probably due to chance.

Occupational exposure to organic dust is unlikely to be a major risk factor of respiratory cancer in Finland. Exposure to wood dust has a minor effect on the risk of nasal cancer in Finland, possibly because this exposure is mainly to softwood dusts. We found that exposure to plant dust may increase the risk of laryngeal cancer. We found support to the finding that exposure to plant dust and animal dust (mainly among farmers) and textile dust decreases the risk of lung cancer. There were no increased risks of respiratory tract cancers among workers exposed to pulp/paper, leather, or synthetic polymer dust.

Acknowledgements

Contract grant sponsor Finnish Work Environment Fund, grant number 105037.

Abbreviations

CE - cumulative exposure

FCR - Finnish Cancer Registry

ILO - International Labour Organization

ISCO - International Standard Classification of Occupations

PID - personal identifier

SES - socioeconomic status

SIR - standardised incidence ratio

Footnotes

Competing interests: none declared.

References

  • 1.Rom W N, Renzetti A D.Environmental and occupational medicine. First edition. Boston: Little Brown & Co, 1983
  • 2.IARC Wood, leather and some associated industries. Lyon: IARC, 1981 [PubMed]
  • 3.IARC Some flame retardants and textile chemicals, and exposures in the textile manufacturing industry. Lyon: IARC, 1990 [PMC free article] [PubMed]
  • 4.IARC Wood dust and formaldehyde. Lyon: IARC, 1995
  • 5.Richiardi L, Boffetta P, Simonato L.et al Occupational risk factors for lung cancer in men and women: a population‐based case‐control study in Italy. Cancer Causes Control 200415285–294. [DOI] [PubMed] [Google Scholar]
  • 6.Miller B A, Blair A, Reed E J. Extended mortality follow‐up among men and women in a U.S. furniture workers union. Am J Ind Med 199425537–549. [DOI] [PubMed] [Google Scholar]
  • 7.Langseth H, Andersen A. Cancer incidence among male pulp and paper workers in Norway. Scand J Work Environ Health 20002699–105. [DOI] [PubMed] [Google Scholar]
  • 8.Jäppinen P, Hakulinen T, Pukkala E.et al Cancer incidence of workers in the Finnish pulp and paper industry. Scand J Work Environ Health 198713197–202. [DOI] [PubMed] [Google Scholar]
  • 9.Jäppinen P, Pukkala E, Tola S. Cancer incidence of workers in a Finnish sawmill. Scand J Work Environ Health 19891518–23. [DOI] [PubMed] [Google Scholar]
  • 10.Kauppinen T P, Partanen T J, Hernberg S G.et al Chemical exposures and respiratory cancer among Finnish woodworkers. Br J Ind Med 199350143–148. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 11.Demers P, Boffetta P. eds. Cancer risk from occupational exposure to wood dust: a pooled analysis of epidemiological studies. In: Pooled analyses of epidemiologic studies. Lyon: IARC, 1998
  • 12.Andersson E, Nilsson T, Persson B.et al Mortality from asthma and cancer among sulfite mill workers. Scand J Work Environ Health 19982412–17. [DOI] [PubMed] [Google Scholar]
  • 13.Boffetta P, Colin D.IARC multicentric study on cancer risk among workers in the pulp and paper industry. Lyon: IARC, 1999
  • 14. Population Census 1970: occupation and social position: official statistics of Finland VI C:104. Helsinki: Central Statistical Office of Finland, 1974
  • 15.Classification of occupations 1980. Helsinki: Central Statistical Office of Finland, 1981
  • 16.Helakorpi S, Patja K, Prättälä R.et alHealth behaviour and health among the Finnish adult population. (in Finnish). National Public Health Institute 2003
  • 17.Korhonen P, Malila N, Pukkala E.et al The Finnish Cancer Registry as follow‐up source of a large trial cohort—accuracy and delay. Acta Oncol 200241381–388. [DOI] [PubMed] [Google Scholar]
  • 18.Teppo L, Pukkala E, Lehtonen M. Data quality and quality control of a population‐based cancer registry. Experience in Finland. Acta Oncol 199433365–369. [DOI] [PubMed] [Google Scholar]
  • 19.Kauppinen T, Toikkanen J, Pukkala E. From cross‐tabulations to multipurpose exposure information systems: a new job‐exposure matrix. Am J Ind Med 199833409–417. [DOI] [PubMed] [Google Scholar]
  • 20.Pukkala E, Guo J, Kyyronen P.et al National job‐exposure matrix in analyses of census‐based estimates of occupational cancer risk. Scand J Work Environ Health 20053197–107. [DOI] [PubMed] [Google Scholar]
  • 21.Hernberg S, Westerholm P, Schultz‐Larsen K.et al Nasal and sinonasal cancer. Connection with occupational exposures in Denmark, Finland and Sweden. Scand J Work Environ Health 19839315–326. [DOI] [PubMed] [Google Scholar]
  • 22.Magnani C, Comba P, Ferraris F.et al A case‐control study of carcinomas of the nose and paranasal sinuses in the woolen textile manufacturing industry. Arch Environ Health 19934894–97. [DOI] [PubMed] [Google Scholar]
  • 23.Nylander L A, Dement J M. Carcinogenic effects of wood dust: review and discussion. Am J Ind Med 199324619–647. [DOI] [PubMed] [Google Scholar]
  • 24.Luce D, Leclerc A, Begin D.et al Sinonasal cancer and occupational exposures: a pooled analysis of 12 case‐control studies. Cancer Causes Control 200213147–157. [DOI] [PubMed] [Google Scholar]
  • 25.'tMannetje A, Kogevinas M, Luce D.et al Sinonasal cancer, occupation, and tobacco smoking in European women and men. Am J Ind Med 199936101–107. [DOI] [PubMed] [Google Scholar]
  • 26.Hildesheim A, Dosemeci M, Chan C C.et al Occupational exposure to wood, formaldehyde, and solvents and risk of nasopharyngeal carcinoma. Cancer Epidemiol Biomarkers Prev 2001101145–1153. [PubMed] [Google Scholar]
  • 27.Elci O C, Akpinar‐Elci M, Blair A.et al Occupational dust exposure and the risk of laryngeal cancer in Turkey. Scand J Work Environ Health 200228278–284. [DOI] [PubMed] [Google Scholar]
  • 28.Berrino F, Richiardi L, Boffetta P.et al Occupation and larynx and hypopharynx cancer: a job‐exposure matrix approach in an international case‐control study in France, Italy, Spain and Switzerland. Cancer Causes Control 200314213–223. [DOI] [PubMed] [Google Scholar]
  • 29.Siemiatycki J, Richardson L, Gerin M.et al Associations between several sites of cancer and nine organic dusts: results from an hypothesis‐generating case‐control study in Montreal, 1979–1983. Am J Epidemiol 1986123235–249. [DOI] [PubMed] [Google Scholar]
  • 30.Gustavsson P, Jakobsson R, Johansson H.et al Occupational exposures and squamous cell carcinoma of the oral cavity, pharynx, larynx, and oesophagus: a case‐control study in Sweden. Occup Environ Med 199855393–400. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 31.Laforest L, Luce D, Goldberg P.et al Laryngeal and hypopharyngeal cancers and occupational exposure to formaldehyde and various dusts: a case‐control study in France. Occup Environ Med 200057767–773. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 32.Andersen A, Barlow L, Engeland A.et al Work‐related cancer in the Nordic countries. Scand J Work Environ Health 199925(Suppl 2)1–116. [PubMed] [Google Scholar]
  • 33.Toren K, Sallsten G, Jarvholm B. Mortality from asthma, chronic obstructive pulmonary disease, respiratory system cancer, and stomach cancer among paper mill workers: a case‐referent study. Am J Ind Med 199119729–737. [DOI] [PubMed] [Google Scholar]
  • 34.Korhonen K, Liukkonen T, Ahrens W.et al Occupational exposure to chemical agents in the paper industry. Int Arch Occup Environ Health 200477451–460. [DOI] [PubMed] [Google Scholar]
  • 35.Pukkala E, Notkola V. Cancer incidence among Finnish farmers, 1979–93. Cancer Causes Control 1997825–33. [DOI] [PubMed] [Google Scholar]
  • 36.Mastrangelo G, Grange J M, Fadda E.et al Lung cancer risk: effect of dairy farming and the consequence of removing that occupational exposure. Am J Epidemiol 20051611037–1046. [DOI] [PubMed] [Google Scholar]
  • 37.Rylander R. Endotoxin in the environment—exposure and effects. J Endotoxin Res 20028241–252. [DOI] [PubMed] [Google Scholar]
  • 38.Mastrangelo G, Fedeli U, Fadda E.et al Epidemiologic evidence of cancer risk in textile industry workers: a review and update. Toxicol Ind Health 200218171–181. [DOI] [PubMed] [Google Scholar]
  • 39.Luce D, Gerin M, Morcet J F.et al Sinonasal cancer and occupational exposure to textile dust. Am J Ind Med 199732205–210. [DOI] [PubMed] [Google Scholar]
  • 40.Teschke K, Morgan M S, Checkoway H.et al Surveillance of nasal and bladder cancer to locate sources of exposure to occupational carcinogens. Occup Environ Med 199754443–451. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 41.Hodgson J T, Jones R D. Mortality of workers in the British cotton industry in 1968–1984. Scand J Work Environ Health 199016113–120. [DOI] [PubMed] [Google Scholar]
  • 42.Shannon H S, Jamieson E, Julian J A.et al Mortality of glass filament (textile) workers. Br J Ind Med 199047533–536. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 43.Fu H, Demers P A, Costantini A S.et al Cancer mortality among shoe manufacturing workers: an analysis of two cohorts. Occup Environ Med 199653394–398. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 44.Merler E, Baldasseroni A, Laria R.et al On the causal association between exposure to leather dust and nasal cancer: further evidence from a case‐control study. Br J Ind Med 19864391–95. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 45.Mikoczy Z, Schutz A, Stromberg U.et al Cancer incidence and specific occupational exposures in the Swedish leather tanning industry: a cohort based case‐control study. Occup Environ Med 199653463–467. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 46.Blair A, Zahm S H. Agricultural exposures and cancer. Environ Health Perspect 1995103(Suppl 8)205–208. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 47.Boffetta P, Gridley G, Gustavsson P.et al Employment as butcher and cancer risk in a record‐linkage study from Sweden. Cancer Causes Control 200011627–633. [DOI] [PubMed] [Google Scholar]
  • 48.Olenchock S A, May J J, Pratt D S.et al Presence of endotoxins in different agricultural environments. Am J Ind Med 199018279–284. [DOI] [PubMed] [Google Scholar]
  • 49.Rask‐Andersen A, Malmberg P, Lundholm M. Endotoxin levels in farming: absence of symptoms despite high exposure levels. Br J Ind Med 198946412–416. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 50.Reif J, Pearce N, Fraser J. Cancer risks in New Zealand farmers. Int J Epidemiol 198918768–774. [DOI] [PubMed] [Google Scholar]
  • 51.Mastrangelo G, Marzia V, Marcer G. Reduced lung cancer mortality in dairy farmers: is endotoxin exposure the key factor? Am J Ind Med 199630601–609. [DOI] [PubMed] [Google Scholar]
  • 52.Schimberg R, Uitti J, Kotimaa M.et al Airborne particulate matter, fungi, bacteria and endotoxins in fur farming. Staub ‐ Reinhaltung der Luft 199252457–460. [Google Scholar]
  • 53.IARC Some organic solvents, resin monomers and related compounds, pigments and occupational exposures in paint manufacture and painting. Lyon: IARC, 1989 [PMC free article] [PubMed]
  • 54.Benke G, Sim M, Fritschi L.et al Comparison of occupational exposure using three different methods: hygiene panel, job exposure matrix (JEM), and self reports. Appl Occup Environ Hyg 20011684–91. [DOI] [PubMed] [Google Scholar]
  • 55.Kolari R. Occupational mobility in Finland 1975/1980/1985 (in Finnish). Central Statistical Office of Finland 1989188
  • 56.Notkola V, Pajunen A, Leino‐Arjas P. Scaffolding, factor or office—study of mortality and disability by occupations (in Finnish). Finnish Official Statistics, Health. Helsinki: Central Statistical Office, 1995261

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