incidence of occupational asthma by occupation and industry in finland
TRANSCRIPT
AMERICAN JOURNAL OF INDUSTRIAL MEDICINE 37:451±458 (2000)
Incidence of Occupational Asthmaby Occupation and Industry in Finland
Antti Karjalainen, MD, PhD,1� Kari Kurppa, MD, PhD,1 Simo Virtanen, PhD,1
Helena Keskinen, MD,2 and Henrik Nordman, MD, PhD2
Background Systematic research on occupation or industry-speci®c incidence ofoccupational asthma (OA) is sparse. We calculated the incidence of noti®ed OA byoccupation, industry and causative agent in Finland for the years 1989±95.Methods The numbers of cases of reported OA were retrieved from the Finnish Registryof Occupational Diseases for the population between 20 and 64 years of age. Thenumbers of employed workers were retrieved from Statistics Finland. Incidence rateswere calculated for each occupation, industry and the total workforce.Results Altogether 2602 cases of OA were noti®ed and the mean annual incidence ratewas 17.4 cases/100,000 employed workers. The incidence rate was the highest in bakers,other painters and lacquerers, veterinary surgeons, chemical workers, farmers, animalhusbandry workers, other food manufacturing workers, welders, plastic product workers,butchers and sausage makers, and ¯oor layers. Cases caused by animal epithelia, hairsand secretions or ¯ours, grains, and fodders accounted for 60% of the total.Conclusions Estimation of occupation and industry-speci®c incidence rates forms thebasis for successful prevention of OA, but necessitates collection of data over severalyears from well-established surveillance systems. Am. J. Ind. Med. 37:451±458,2000. ß 2000 Wiley-Liss, Inc.
KEY WORDS: occupational asthma; incidence; occupation; industry; surveillance;work-related
INTRODUCTION
Asthma is the most common occupational lung disease
in high-income countries [Venables and Chan-Yeung,
1997]. It affects economically active populations and has
important socioeconomic consequences [Ameille et al.,
1997]. Estimates of the fraction of occupational asthma
(OA) from within the total asthma category vary from
around 3±6% [Kogevinas et al., 1996, 1999; Reijula et al.,
1996; Fishwick et al., 1997] to 15±20% [Kobyashi S, 1974;
Blanc PD, 1987].
Systematic research on incidence rates of OA is sparse.
Such information is laborious to collect because the an-
nual incidence is typically well below 1% even in high-risk
occupations. At present, best overall estimates of OA
incidence in various sectors of working life are based on
surveillance systems which have collected morbidity data
over several years. The accumulation of cases over several
years provides data for risk estimation on occupations and
industrial sectors where OA is relatively rare. Noti®cation
systems have acknowledged weaknesses in coverage and
case ascertainment, typically resulting in underestimates
of occurrence but may also contain a bias towards
overestimation in some circumstances. One of the most
complete national OA noti®cation systems is in Finland (see
Meredith and Nordman [1996]). In Finland asthma is con-
sidered an occupational disease if its speci®c etiology is an
1Department of Epidemiology and Biostatistics, Finnish Institute of Occupational Health2Department of Occupational Medicine, Finnish Institute of Occupational Health*Correspondence to: Antti Karjalainen, Finnish Institute of Occupational Health,
Topeliuksenkatu 41aA, FIN-00250 Helsinki, Finland.E-mail: [email protected]
Accepted13 December1999
ß 2000Wiley-Liss, Inc.
exposure at work, but not in case of just work-related
exacerbation of an existing disease. We report the incidence
of noti®ed OA by occupation, industry and causative agent
in Finland for the years 1989±95.
MATERIAL AND METHODS
The Finnish Registry of Occupational Diseases (FROD)
was established in 1964. The registry is maintained by the
Finnish Institute of Occupational Health. Reporting of all
known or suspected occupational diseases to provincial
labor protection authorities is compulsory for Finnish
physicians. In addition to the reports forwarded by the
labor protection authorities, FROD receives noti®cations of
every new case reported to the insurance companies as an
occupational disease. Information from these two sources is
combined so that each new occupational disease is recorded
only once.
In Finland, all employees must be insured against
occupational diseases and accidents at work. Since 1982, the
insurance also covers farmers, regardless of their profes-
sional status. According to the 1995 Labour Force Survey,
these occupational groups cover 91% of the active Finnish
workforce [Eurostat, 1997]. In addition, according to data
from the Federation of Accident Insurance Institutions
about 75,000 of the non-agricultural self-employed workers
are insured on a voluntary basis, i.e., about 95% of the total
active workforce (about 2 million) are covered by the
insurance system.
The compensation for a con®rmed occupational disease
is relatively generous; it includes costs of treatment, medical
examinations and retraining as well as various allowances
and pensions. There is, therefore, an incentive for people
whose health has been affected by their job to come
forward. On the other hand, insurance companies require
good evidence of the diagnosis and the causal link before
paying compensation. The diagnosis of OA is carried out by
lung specialists in the Central or University Hospitals or
at the Finnish Institute of Occupational Health. In most
cases, serial respiratory function tests, allergological
tests and inhalation challenge tests are performed. In case
of chemicals or new sensitizing agents, the diagnosis of OA
is centralized to the Finnish Institute of Occupational
Health.
For the years 1989±95, the numbers of cases of
reported OA were retrieved from the Finnish Registry of
Occupational Diseases for each 3-digit level group of the
classi®cation of occupations [Statistics Finland, 1987a] and
each 2-digit level group of the classi®cation of industries
[Statistics Finland, 1987b]. These classi®cations are based
on the International Standard Classi®cation of Occupations,
ISCO [International Labour Of®ce, 1978] and the Interna-
tional Standard Industrial Classi®cation of all Economic
Activities, ISIC [United Nations, 1968]. The numbers of
employed workers in these occupations and industries were
retrieved from Statistics Finland according to the same
classi®cations for each of the years 1989±95. The incidence
rate was calculated by dividing the number of reported cases
by the number of employed workers for each occupation,
industry and the total workforce. The study was restricted to
the population between 20 and 64 years of age. The 95%
con®dence intervals (95% CI) were calculated according to
Poisson distribution.
The noti®cation reports also include information on the
primary causative agent and up to two secondary causative
agents. The causative agents are coded according to a 6-digit
level exposure classi®cation which has been developed at
the Finnish Institute of Occupational Health.
RESULTS
Altogether 2602 cases of OA were noti®ed during
1989±95 (Table I). The median age at noti®cation was 43
years. The mean annual incidence rate was 17.4 cases/
100,000 employed workers. In those aged 20±44 years, the
incidence rate was 14.7 (95% CI 13.7±15.8)/100,000 for
men and 14.2 (13.1±15.3)/100,000 for women. In those
aged 45±64 years, the incidence rate was 21.7 (19.9±23.6)/
100,000 for men and 24.9 (23.0±27.0) for women.
Occupation
In men, the incidence rate was the highest in bakers,
followed by other painters and lacquerers (includes spray
painters) (Table I). The incidence rate exceeded 40/100,000/
yr also for male veterinary surgeons, chemical workers,
farmers, animal husbandry workers, other food manufactur-
ing workers, welders, plastic product workers, butchers and
sausage makers, and ¯oor layers.
In women the incidence rate was highest in bakers
followed by plywood and ®berwood workers and several
farming occupations (Table I).
Industry
Both in men and in women about half of the cases were
reported from agriculture and one-third from manufacturing
(Table II). In addition to these main industries and their
subcategories, high incidence rates were observed in women
in retail trade of special products (includes pharmacies,
¯ower shops etc.) and in other services (includes hair-
dressing).
Agents
Cases caused by animal epithelia, hairs and secretions
or ¯ours, grains, and fodders accounted for 60% of the cases
(Table III).
452 Karjalainen et al.
TABLE I. Number of Cases andMeanAnnual Incidence Rate (/100,000) of Occupational Asthma by Occupationa and Gender in1989^95 in Finland
Men Women
Code Occupation or occupational group N Incid (95%CI) Popul N Incid (95%CI) Popul
0 Professional technical and relatedwork 33 3 (2^4) 185,400 46 5 (4^7) 128,200005 Chemical engineers and technicians 5 8 (3^19) 8594 0 0 (0^28) 1524007 Engineers and technicians in other branches 9 10 (5^19) 12,633 0 0 (0^26) 1656012 Laboratory assistants 1 4 (0^24) 3357 17 28 (16^45) 8641022 Agricultural research and consultativework 2 14 (2^49) 2108 5 43 (14^101) 1647032 Secondary school teachers 6 5 (2^12) 15,687 10 5 (2^9) 29,722035 Kindergarten teachers 0 0 (0^68) 631 6 8 (3^18) 10,457
1 Health care and social work 10 5 (3^10) 26,811 52 3 (2^4) 224,680103 Nurses 0 0 (0^32) 1321 8 3 (1^6) 38,779108 Technical nursing assistants 0 0 (0^118) 363 9 6 (3^11) 22,997121 Dentists 2 20 (2^73) 1409 6 29 (11^64) 2927122 Dental assistants 0 0 (0^5350) 8 6 15 (5^32) 5775141 Veterinary surgeons 5 171 (56^400) 417 1 34 (1^192) 414154 Nurses etc in social welfare institutions 0 0 (0^22) 1914 6 4 (2^10) 19,556
2 Managerial, administrative and clerical work 18 2 (1^3) 129,539 19 1 (1^2) 236,067211 Managers of business enterprises 16 4 (2^6) 64,229 7 6 (2^12) 17,027242 Office personnel 0 0 (0^9) 4552 6 1 (0^3) 66,177
3 Commercial work 16 2 (1^4) 92,446 38 5 (3^7) 110,898332 Sales agency work 3 3 (1^8) 16,643 5 10 (3^24) 6972341 Wholesalers and retailers 0 0 (0^3) 13,757 5 6 (2^14) 12,156343 Shop assistants, shop cashiers 4 3 (1^7) 20,202 24 6 (4^9) 56,986
4 Agricultural, forestry and fishingwork 650 82 (76^89) 112,743 683 162 (150^175) 60,218400 Farmers 591 120 (111^131) 70,121 562 191 (176^208) 41,962406 Animal husbandry work 52 116 (87^152) 6410 104 191 (156^231) 7788409 Other farming and animal husbandry work 1 66 (2^367) 217 6 173 (63^376) 497
5 Transport and communicationwork 11 2 (1^3) 100,958 1 1 (0^3) 25,929541 Lorry and articulated vehicle drivers 10 3 (1^5) 48,546 0 0 (0^51) 837
6^8 Manufacturing,machinery operationwork, etc. 550 21 (19^22) 381,739 322 53 (48^60) 86,040621 Carpenters 14 7 (4^12) 27,746 0 0 (0^810) 53624 Buildingworkers 9 9 (4^16) 15,096 1 23 (1^127) 628625 Floor layers 5 54 (18^126) 1322 0 0 (0^362) 118716 Industrial sewers etc. 0 0 (0^286) 150 21 33 (20^50) 9087751 Turners,mechanists and tool makers 16 15 (8^24) 15,497 0 0 (0^59) 721752 Machine fitters etc. 10 9 (4^16) 16373 0 0 (0^196) 218753 Machine and enginemechanics etc. 25 10 (7^15) 34,556 2 28 (3^100) 1035754 Platers and sheetmetal workers 34 33 (23^46) 14,773 1 72 (2^401) 199755 Plumbers 9 10 (5^20) 12,384 0 ^ ^ 0756 Welders, flame cutters etc. 68 76 (59^96) 12,762 0 0 (0^75) 572757 Machine andmetal product assemblers 2 17 (2^60) 1711 6 49 (18^107) 1740759 Other engineering and structural metal work 8 12 (5^24) 9265 0 0 (0^41) 1043761 Electrical fitters 5 3 (1^7) 22,834 0 0 (0^150) 285765 Electrical equipment assemblers etc. 5 29 (9^67) 2477 31 65 (44^92) 6848772 Sawyers 8 16 (7^32) 7018 1 11 (0^63) 1254773 Plywood and fiberboardworkers 6 64 (23^138) 1348 20 214 (131^331) 1333776 Cabinetmakers and joiners 5 12 (4^29) 5769 1 35 (1^194) 410777 Woodworkingmachine operators 18 33 (20^52) 7795 5 75 (24^174) 958781 Building painters 13 23 (12^39) 8236 0 0 (0^110 390782 Other painters and lacquerers 45 223 (163^299) 2878 4 144 (39^368) 397
Occupational Asthma in Finland 453
Of the 1153 cases in farmers, animal epithelia, etc.
was the primary cause in 798 (69%), ¯ours, grains, and
fodders in 225 (20%) and storage mites in 104 (9%) of
cases. Cow dander (609 cases) was the most common of the
primary causative animal epithelia and barley (108) the
most common of the primary causative ¯ours in farmers.
Two causative agents were mentioned in 12% and three
causative agents in 1% of the noti®cations among farmers.
Animal epithelia etc. was more commonly noti®ed as the
primary cause in female (77% of all) than in male farmers
(62%).
In 211 (97%) of the cases in bakers, ¯ours were
reported as the primary causative agent. In 47% (100 cases)
of these, the type of ¯our was not speci®ed. Among the
remaining cases rye ¯our (55) and wheat ¯our (44) were the
most commonly reported as the primary causative agent.
Only occasionally were enzymes (3), storage mites (2) or
milk powder (2) reported as primary causative agents. Two
causative agents were mentioned in 14% and three causative
agents in 2% of the noti®cations among bakers.
Spray painters are included in the job category ` Other
painters and lacquerers,'' which includes all other painters,
except construction painters. Of the 49 cases in this job
category 65% (32) were due to isocyanates. The remaining
primary causes in this job category were mainly epoxy
resins or epoxy paints (eight cases).
DISCUSSION
The coverage of the Finnish occupational disease
system is quite complete. Nevertheless, about 5% of the
total workforce is not covered by the system, and
noncovered workers may slightly bias the incidence rates
in some risk trades where self-employed workers are
common (e.g., hairdressers, spray painters, dentists). No
quantitative data are available on the fraction of noninsured
workers by occupation or industry. The insurance, however,
offers a relatively good level of social security, which
motivates even self-employed workers to insure themselves
in the high-risk trades. Therefore, the above bias is probably
not important. At least none of the other surveillance
schemes cited in Table IV and with data on occupation or
industry-speci®c rates, have reported higher rates for the
above occupations.
In Finland, the incidence rate of OA is exceptionally
high in farmers. Finnish farmers are exposed to high
airborne concentrations of organic dusts, especially during
winter when the cattle are kept in the cow-houses for 5±8
months. It is also a common practice to brush the cows,
which further increases the exposure levels. About half of
the cases of OA are reported among farmers. The incidence
rates from the national surveillance schemes of OA differ
less for trades other than farming (Table IV). Unfortunately
TABLE I. (continued)
Men Women
Code Occupation or occupational group N Incid (95%CI) Popul N Incid (95%CI) Popul
822 Bakers 101 444 (362^540) 3248 117 408 (337^489) 4101826 Butchers and sausagemakers 14 57 (31^95) 3531 0 0 (0^42) 1017828 Processed foodpreparers 1 137 (3^764) 104 6 138 (51^301) 620829 Other food andbeveragemanufacturingwork 7 99 (40^203) 1015 1 11 (0^60) 1334839 Other chemical processingworkers 12 146 (76^256) 1171 9 143 (66^272) 897852 Plastic product workers 18 68 (40^107) 3782 9 63 (29^120) 2040861 Cast concrete product workers 7 29 (12^61) 3405 0 0 (0^259) 165881 Packers 6 21 (8^46) 4088 31 49 (33^69) 9061882 Warehousemen 7 6 (2^12) 16,694 8 22 (10^44) 5144
9 Serviceworketc. 24 5 (3^7) 74,391 124 11 (9^13) 156,784911 Housekeepingmanagers, snackbarmanagers 0 0 (0^16) 2653 14 16 (9^27) 12,355912 Chefs, cooks and cool buffetmanagers 8 32 (14^64) 3541 22 18 (12^28) 16,998913 Kitchen assistants, restaurantworkers etc. 0 0 (0^38) 1130 9 6 (3^12) 20,527942 Cleaners etc. 1 4 (0^25) 3237 31 8 (6^12) 53,123951 Hairdressers, beauticians etc. 1 33 (1^186) 427 37 37 (26^51) 14,409981 Officers etc. 5 9 (3^20) 8401 0 0 (0^2539) 17
Z Unknown 2 8 (1^29) 3570 3 19 (4^54) 2309All 1314 17 (16^18) 1,107,586 1288 18 (17^19) 1,031,178
aFinnish Classification of Occupations 1987 [Statistics Finland 1987a]. Allmajor categories, and 3-digit categorieswith at least 5 notifications in either sex in 1989^95.
454 Karjalainen et al.
TABLE II. Numberof Cases andMean Annual Incidence Rate (/100,000) of Occupational Asthma by Industry a and Gender in1989^95 in Finland
Men Women
Code Industry N Incid (95%CI) Popul N Incid (95%CI) Popul
A Agriculture, fishing and trapping 649 109 (101^118) 85,100 677 168 (156^181) 57,54301 Agriculture 649 112 (103^121) 82,876 676 169 (157^183) 57,029
B Forestry and logging 0 0 (0^2) 26,839 0 0 (0^18) 2409C Mining and quarrying 1 4 (0^21) 3757 1 36 (1^199) 400D Manufacturing 474 23 (21^25) 293,318 358 35 (31^39) 146,63111 Food, beverage and tobaccomanufacture 145 75 (64^89) 27,516 176 94 (81^109) 26,69712 Textilesmanufacture 3 13 (3^39) 3243 12 24 (12^42) 714913 Wearing apparel, leather goods and footwear manufacture 4 20 (5^51) 2848 27 23 (15^34) 16,59114 Wood andwoodproductsmanufacture 48 25 (18^33) 27,367 36 71 (50^98) 725215 Pulp, paper andpaper productsmanufacture 12 5 (3^9) 33,436 6 8 (3^17) 10,68016 Publishing andprinting 2 1 (0^5) 20234 6 5 (2^10) 18,63717 Furnituremanufacture 11 19 (9^34) 8332 5 18 (6^42) 396418 Chemicals and chemical productsmanufacture 21 24 (15^37) 12,387 19 36 (22^56) 751721 Rubber andplastic productsmanufacture 25 38 (25^57) 9322 9 28 (13^53) 463122 Glass, clay and stone productsmanufacture 14 14 (8^24) 13,976 4 14 (4^37) 396823 Basic metal industries 16 19 (11^31) 11,792 3 17 (3^49) 255224 Fabricatedmetal productsmanufacture 81 35 (28^44) 32,928 10 21 (10^39) 669825 Machinery and equipmentmanufacture 44 16 (11^21) 39,857 4 8 (2^20) 725926 Electrical products and instrumentsmanufacture 19 11 (6^17) 25,328 36 32 (22^44) 16,17527 Transport equipmentmanufacture 22 17 (11^26) 18,378 4 18 (5^45) 326129 Other manufacturing industries 5 18 (6^42) 3943 0 0 (0^16) 2758
E Energy andwater supply 6 4 (2^9) 20,464 0 0 (0^9) 479631 Electricity supply 5 4 (1^9) 18,116 0 0 (0^10) 4292
F Construction 57 6 (5^8) 136,770 2 2 (0^7) 14,04135 Building construction 32 7 (5^9) 68,059 2 5 (1^16) 633536 Building installation and finishingwork 18 8 (4^12) 34,065 0 0 (0^12) 344437 Land andwater construction 6 3 (1^6) 31,456 0 0 (0^18) 2322
G Wholesale and retail trade 47 5 (4^7) 127,936 32 4 (2^5) 129,01541 Wholesale trade 5 2 (0^4) 47,016 4 2 (1^6) 24,89743 Retail trade 2 1 (0^2) 41,637 20 3 (2^5) 92,94544 Retail trade 4 22 (6^57) 2546 7 326 (131^672) 30645 Wholesale and retail trade, service and repair ofmotor vehicles 34 15 (10^21) 32,772 1 2 (0^10) 8366
H Hotels and restaurants 15 15 (8^24) 14,734 29 9 (6^13) 45,40847 Hotel and other accommodation industry 1 3 (0^18) 4337 10 14 (7^27) 989348 Restaurant industry 14 19 (11^32) 10,396 19 8 (5^12) 35,515
I Transport 8 1 (1^2) 93,151 2 1 (0^4) 24,550J Communication 1 1 (0^3) 27,106 1 1 (0^4) 19,153K Finance and insurance 0 0 (0^2) 18,377 2 1 (0^2) 54,327L Real estate, cleaning and rental services 4 2 (1^5) 26,606 11 5 (3^10) 28,99166 Cleaning and laundry services 2 3 (0^9) 11,329 8 6 (3^13) 17,713
M Technical andbusiness services 6 2 (1^4) 49,624 6 3 (1^6) 33,47276 Other business services 4 7 (2^19) 7629 6 13 (5^28) 6731
N Public administration and defense 15 3 (2^6) 61,865 23 6 (4^8) 59,31281 Public administration 4 2 (1^5) 27,085 10 3 (1^6) 46,47182 Public order and safety 8 5 (2^11) 20,826 12 21 (11^37) 8137
O Education and research 17 5 (3^7) 53,510 29 4 (3^6) 96,51285 Education 14 4 (2^7) 45,736 24 4 (2^6) 90,50986 Research and development 3 6 (1^16) 7774 5 12 (4^28) 6002
Occupational Asthma in Finland 455
TABLE II. (continued)
Men Women
Code Industry N Incid (95%CI) Popul N Incid (95%CI) Popul
P Health and social welfare services 7 3 (1^7) 30,431 64 4 (3^5) 252,64387 Health andmedical services 7 4 (2^9) 22,307 52 6 (4^7) 134,33788 Social welfare services 0 0 (0^5) 8124 12 1 (1^3) 118,306
R Recreational and cultural services 5 3 (1^8) 20,953 7 5 (2^10) 20,963S Organizational and religious services 1 1 (0^7) 11,471 5 3 (1^8) 20,850T Other services 1 5 (0^26) 3116 39 31 (22^42) 18,262X Unknown industry 0 0 (0^17) 2449 0 0 (0^23) 1892
All 1314 17 (16^18) 1,107,586 1288 18 (17^19) 1,031,178
aClassification of Industries 1988 [Statistics Finland 1987b]. Allmajor categories, and 2-digit categorieswith at least 5 notifications in either sex in 1989^95.
TABLE III. Number of Cases of Occupational Asthma by Primary Causative Agent in1989^95 in Finland
Men Women AllAgent N N N (%)
Animal epithelia, hairs or secretions 438 542 980 (37.7)Flours, grains, fodders 282 297 579 (22.3)Mites 82 55 137 (5.3)Di-isocyanates 103 21 124 (4.8)Welding fumes etc. 106 8 114 (4.4)Wood dusts 49 20 69 (2.7)Molds 13 54 67 (2.6)Formaldehyde 21 25 46 (1.8)Hairdressing chemicals 2 35 37 (1.4)Textiles 2 30 32 (1.2)Synthetic resins andplastics (e.g., epoxides) 20 11 31 (1.2)Plants 11 17 28 (1.1)Synthetic glues and acrylates 8 18 26 (1.0)Enzymes 11 13 24 (0.9)Natural resins, balsams etc. (except latex) 7 14 21 (0.8)Chromium groupmetals and their compounds 20 0 20 (0.8)Paints 14 1 15 (0.6)Carboxylic acid anhydrides 9 5 14 (0.5)Cobalt, nickel and their compounds 11 3 14 (0.5)Amines 3 8 11 (0.4)Detergents 1 9 10 (0.4)Latex 2 7 9 (0.3)Milk powder,meat, fish etc. 3 5 8 (0.3)Pharmaceuticals 1 6 7 (0.3)Cement, concrete 5 1 6 (0.2)Phtalic acid 1 4 5 (0.2)Oils and lubricants 4 1 5 (0.2)Varnishes 2 3 5 (0.2)Printing inks 1 4 5 (0.2)Unknown 42 17 59 (2.3)Others 40 54 94 (3.6)All 1314 1288 2602 (100)
456 Karjalainen et al.
many of the reports from other surveillance systems do not
present the data in a way that would enable detailed
comparison by occupation or industry. Relatively compar-
able job category-speci®c data are available from Sweden
[ToreÂn K, 1996]. Despite the very different data collection
procedures, the incidence rates in Sweden and Finland are
quite similar, except for farmers.
National surveillance systems for OA are based either
on self-reporting [ToreÂn K, 1996], reporting by trained
physicians [Gannon and Burge, 1991; Meredith and
McDonald, 1994] or data from compensation schemes
[Baur et al., 1998a] or combinations of these. The de®nition
of OA is obviously somewhat different between these
schemes. Further dif®culties for comparison of data from
the national surveillance schemes are caused by the
heterogeneity of the various classi®cations used in the
reporting of data. Standard international classi®cations
are available for occupation and economic activity (indus-
try) but are not always used in a completely standard way
due to national modi®cations. There is no widely applied
international classi®cation for the causative agent or the
industrial application of the causative product. More
data should also be available on the diagnostic criteria
used for OA and the reporting guidelines used by the
various surveillance schemes. Successful primary and
secondary prevention of OA relies on information from
surveillance systems. Therefore, harmonization of the
de®nitions and classi®cations used in the reporting should
be enhanced.
Any reporting system for occupational or work-related
diseases is inevitably in¯uenced by the national system
dealing with compensation of occupational diseases. Cases
caused by well-established causative agents are more likely
to be compensated and are, therefore, also more readily
reported. In OA further bias may result from the fact that
it is easier to justify causality at individual levels for
sensitizing than for nonsensitizing agents. The incidence
rates from OA surveillance schemes are therefore lower than
estimates calculated from the etiologic fractions of case-
control studies. In prevention of asthma, the medico-legal
de®nition of sensitization related OA is not ideal. It would
be useful to also consider asthma resulting from exposure to
irritants in the workplace as well as preexisting asthma
exacerbated by workplace environmental exposures
[Wagner and Wegman, 1998]. Such an enlargement of the
de®nition of OA may not be justi®able for medico-legal
purposes [Malo and Chan-Yeung, 1998], but surveillance
systems taking into account all components of work-related
excess of asthma should be developed to enhance prevention
and management of asthma at workplace [Baur et al.,
1998b; Milton et al., 1998]. Unlike many other chronic
conditions primarily affecting older persons, asthma dis-
proportionately affects those of working age and causes
some degree of work disability in as many as 40% of
asthmatic adults [Blanc et al., 1993, 1996].
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Incidence rate (/million/yr) Most commoncausative agent
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Occupational Asthma in Finland 457
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