Work-Related Asthma in Washington State


Asthma is a serious, common, and costly lung disease. Workplace exposures likely cause a large proportion of new onset asthma cases in adults. Over 350 workplace substances are known sensitizers for occupational asthma. Occupational asthma is more severe than non-occupational asthma leading to higher health care utilization and poorer asthma control.

The Washington State Department of Labor and Industries Safety and Health Assessment and Research for Prevention (SHARP) program, conducts work-related asthma surveillance for Washington State. From October 2001 through December 2008, there were a total of 1,343 work-related asthma claims captured by the surveillance system (which includes both workers' compensation claims and physician reporting). SHARP conducted follow-up telephone interviews for 604 of these 1,343 cases. The total cost of the 1,285 workers' compensation claims captured by the surveillance system was approximately $11 million dollars.


Most claimants (89%) were between 25-64 years old and slightly more than half (57%) were female.

Accepted claims can be categorized into compensable and noncompensable claims. Compensable claims are those with the claim status codes "compensable", "kept on salary", "total permanent disability", "fatal", or "loss of earning power." Accepted claims that are noncompensable are medical-only claims. Among the 1,285 workers' compensation asthma claims, 37% were rejected by L&I, 40.1% were non-compensable, and 17.8% were compensable.

By occupation, the majority of asthma claimants were Production workers (14%) and Office & Administrative Support (13%). Healthcare and Healthcare support occupations totaled (11%) collectively, followed by occupations related to Transportation (8%) and Construction (7%). By 2-digit North American Industry Classification System (NAICS) Industry Sector codes (see Table 1), most claims filed were from the Manufacturing Sector (16%) followed by Health Care and Social Assistance (15%). Educational Services and Public Administration each represent 10% of the claims while all other 2-digit sectors make up less than nine percent of the remaining claims (see Table 1). The source agent(s) causing most of the asthma differs between industries. The Manufacturing sector has the most diverse list of asthma sources. Asthma in Manufacturing predominantly resulted from exposure to Plant Material such as Western Red Cedar & Wood Dust NOS (Not Otherwise Specified), reflecting the role of the wood products industry in Washington. In Health Care, asthma claims were dominated by Miscellaneous Chemicals more than in other industries. The predominant asthma sources in Educational Services and Public Administration were very similar to those in Health Care and driven by exposure to NOS Mold, NOS Dust, Indoor Air Pollutants and Indoor Air Pollutants from Building Renovation. Plant Material and Miscellaneous Chemicals were the predominant asthma sources in Agriculture. In Construction, Plant Material (wood dust) and Mineral & Inorganic Dusts are the predominate sources, followed by Miscellaneous Chemicals.

The exposure sources for all asthma claims are summarized here grouped at the 3 digit AOEC code level (see Table 2). This hierarchy shows the dominant exposure source in WA is 2 "Miscellaneous Chemicals and Materials, Referenced by Use." This makes sense as this category includes a large number of generic exposure subcategories such as: Indoor Air Pollutants, Indoor Air Pollutants from Building Renovation, NOS Chemicals, NOS Paints, NOS Perfume, and NOS Cleaning Materials.

Asthma was classified for claims with a follow-up interview (n=604). Approximately 55% of interviewed workers suffered from New Onset Asthma (NOA, asthma caused solely by exposures in the workplace). Nearly 80% of these NOA cases (44% of the total) would be characterized as occupational asthma with latency and the remaining 20% (11% of total cases) would be characterized as occupational asthma without latency or Reactive Airways Dysfunction Syndrome (new-onset asthma caused by a one-time high-dose workplace irritant exposure). Another 44% of cases were classified as Work-Aggravated Asthma (WAA, pre-existing asthma that is made worse by workplace exposures).

Focus on Plant Material Exposures and Isocyanates

There were a total of 134 claims filed for exposure to plant material. Asthma from Plant Materials occurs in 15 out of 20 NAICS Sectors in Washington. Plant Materials are the dominant asthma source for Agriculture, Forestry, Fishing & Hunting; Construction; Manufacturing; and Transportation & Warehousing. It is the second most common asthma agent in Wholesale Trade. Washington State also has perhaps more industries that involve the manufacturing, processing, and handling of plant asthmagens compared to other states. Western Red Cedar is the most common plant asthmagen with 41 cases and exposure is occurring across 5 different sectors. There were 8 cases reported for asthma to Hops in Agriculture, with 5 additional Hops cases reported by the agriculture-related industries of Wholesale Trade and Transportation and Warehousing. Other plant materials causing asthma include NOS Wood Dust, Paper Dust, Hay, and Capsicum. In compensable claims the median claim cost and median time loss days were significantly higher for plant material related claims than for claims with other exposure sources (both p<0.01). For non-compensable claims, the median claim costs were not significantly higher for plant material claims than claims with other exposure sources. Because they can cost more in both claim costs and days of time loss, reducing the number of these claims through prevention would be beneficial both for workers and employers.

In addition to Plant Materials, we chose an in-depth focus on Isocyanate asthma. The SHARP program has been conducting research on isocyanates in the Collision Repair Industry since 2005. In addition, L&I's DOSH program has conducted local emphasis enforcement inspections on methylene diisocyanate (MDI) exposures in the truck bed lining industry. There were a total of 24 claims filed for exposure to isocyanates. Most claims were filed by Automotive Body industry. A total of 10 isocyanate asthma claims were filed from the Manufacturing sector.


The surveillance of work-related asthma in Washington suggests that prevention resources are required in a wide variety of industries and for exposure to a wide variety of sources.

  • From an industry perspective, Manufacturing and Health Care have the highest number of asthma cases. Manufacturing requires prevention from sources such as Miscellaneous Chemicals and Plant Materials while Health Care requires asthma prevention from sources including Molds, Indoor Environmental Quality (i.e. Perfume), and Cleaning Materials.
  • There were some differences noted in industry sector and exposure agents between asthma classifications. Prevention efforts should address agents causing NOA, and the most frequent sources causing NOA include: Minerals & Inorganic Dusts, Isocyanates, and Plant Materials.
  • Unlike other U.S. States conducting work-related asthma surveillance, Plant Materials are a major source of work-related asthma in Washington. They are seen in Agriculture (Hops production) and Agriculture-related Warehouse and Transportation industries. Plant materials are also a frequent exposure source in Manufacturing, due to red cedar and other wood dust exposures in primary and secondary wood processing. Plant Materials, along with a high number of cases for exposure to Mold, reflect the nature of Washington's industries and climate.
  • An in-depth focus on isocyanate exposures revealed that prevention is needed for paint spray application on large or awkward objects that do not fit inside a spray booth; six isocyanate claims referenced working on objects like aircraft parts or fire engines at the time of exposure.


Washington's work-related asthma surveillance system provides insight into causative agents, many of which are unique or commonly handled in our geographic region, that cause respiratory illness in our state. The system can help direct prevention resources to workers who, because of their occupation or the materials they handle, are at high risk for the burden of work-related asthma.

Want More Information?

Please contact SHARP for a complete copy of the most-recent asthma Technical Report (2010), or see: Work-Related Asthma in Washington State: A summary of SHARP's asthma surveillance data 2001-2008 (39 KB PDF) summary only.

See the Work-related asthma section on the SHARP's publications page for links to other asthma information.

Contact SHARP for questions about SHARP's work‑related asthma program.

Table 1
Number of Claims by 2-Digit NAICS Industry Sector
Industry Sector # %
11 — Agriculture, Forestry, Fishing and Hunting 61 4.7.
21 — Mining, Quarrying, and Oil and Gas Extraction 1 <1.
22 — Utilities 4 <1.
23 — Construction 86 6.61.
31-33 — Manufacturing 210 16.13.
42 — Wholesale Trade 47 3.61.
44-45 — Retail Trade 110 8.45.
48-49 — Transportation and Warehousing 36 2.76.
51 — Information 16 1.23.
52 — Finance and Insurance 31 2.38.
53 — Real Estate and Rental and Leasing 24 1.84.
54 — Professional, Scientific, and Technical Services 29 2.23.
56 — Administrative and Support and Waste Management and Remediation Services 96 7.37.
61 — Educational Services 131 10.06.
62 — Health Care and Social Assistance 189 14.52.
71 — Arts, Entertainment, and Recreation 9 <1.
72 — Accommodation and Food Services 53 4.07.
81 – Other Services (except Public Administration) 38 2.92.
92 — Public Administration 131 10.06.
Total 1302 100.

An additional 41 claims had no industry information reported (13 physician reported cases, 1 Self-Insured without claim information and 27 workers' compensation claims that lacked any NAICS information). One industry sector, NAICS 55 – Management of Companies and Enterprises, did not appear in our data. Not all claims with a reported industry sector had agent/source information, and claims may report multiple sources.

Table 2
Frequency of Major Groups of Exposure Agents
Rank AOEC* Code — Description All primary sources
1 320 — Miscellaneous Chemicals and Materials, Referenced By Use 494.
2 010 — Mineral and Inorganic Dusts 182.
3 370 — Plant Material 164.
4 390 — Microorganisms 142.
5 330 — Pyrolysis Products 111.
6 170 — Hydrocarbons, Not Otherwise Specified 85.
7 020 — Metals and Metalloids 50.
8 380 — Animal Material 48.
9 060 — Aliphatic and Alicyclic Hydrocarbons 44.
10 360 — Ergonomic Factors (Exercise) 36.
11 050 — Acids, Bases, and Oxidizing Agents 27.
12 220 — Isocyanates 27.
13 040 — Miscellaneous Inorganic Compounds 24.
14 270 — Polymers 23.
15 130 — Ketones 18.
16 030 — Halogens (Inorganic) 16.
17 350 — Physical Factors 14.
18 160 — Aromatic Hydrocarbons 11.
19 110 — Epoxy Compounds 9.
20 120 — Aldehydes and Acetals 9.
21 070 — Alcohols 6.
22 190 — Halogenated Aliphatic Hydrocarbons (except Organochlorine Pesticides) 4.
23 140 — Esters 3.
24 090 — Glycol Ethers 2.
25 180 — Phenols and Phenolic Compounds 2.
26 080 — Glycols 1.
27 150 — Carboxylic Acids and Anhydrides 1.
28 250 — Aromatic Nitro and Amino Compounds (including Heterocyclic) 1.
29 310 — Organic Sulfur Compounds 1.
Grand Total 1,555.

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