Workers' compensation insurance is mandated for all non-federal employers in Washington State unless they are covered by an alternative workers’ compensation program (e.g., Federal Employees' Compensation Act, Longshoremen's and Harbor Workers' Compensation Act). Workers' compensation insurance can be obtained through either (a) the state's industrial State Fund (SF) insurance program administered by the Department of Labor & Industries (L&I) or (b) through self-insurance. The State Fund provides coverage for approximately 1.9 million (about two-thirds) of the workers in the state and 99.7% of all employers. The remaining 450 employers self-insure for workers' compensation. To self-insure, employers must have at least $25 million in assets, an effective accident-prevention program, a minimum of 3 years of business operations, and specific liquidity requirements.⁽³⁶⁾ Specific occupations and employers that are exempted from mandatory workers' compensation include domestic workers and sole proprietors such as specialty trade contractors.⁽³⁶⁾

Distinction between State Fund and self-insured workers is made because while data from both programs are collected into L&I's Workers' Compensation database, less information about self-insurance claims (medical records and claim costs) is typically reported to the state. Because of this, the surveillance system described here reflects primarily State Fund-insured workers. Occupational asthma is a reportable condition in Washington State for health care providers and health care facilities.⁽³⁷⁾ Cases are to be reported directly to the Safety and Health Assessment and Research for Prevention (SHARP) program, regardless of the insurance source, through confidential case reporting.

Washington State's asthma surveillance system has been described in detail.⁽⁷⁾ In brief, the surveillance system extracts monthly those workers' compensation claims from the Workers' Compensation database with the word “asthma” (or its misspelling) on the Report of Industrial Injury or Occupational Disease (RIIOD) claim form. Claims are reviewed and educational materials are sent to each claimant. Cases are interviewed by telephone to obtain additional data on workplace exposures and medical history. The surveillance protocols, phone interview, and educational materials were approved by the Washington State Institutional Review Board.

Two primary goals of the surveillance system are to classify the type of asthma and to document the agent causing the asthma. This information is obtained through a questionnaire administered over the telephone with the injured worker. The questionnaire incorporates the Sentinel Event Notification System for Occupational Risks (SENSOR) case classification scheme for occupational asthma adopted by the National Institute for Occupational Safety and Health (NIOSH).⁽³⁸⁾ There are three SENSOR asthma classifications including: Work-Aggravated Asthma (WAA), New-Onset Asthma with latency (NOA), and new-onset asthma without latency known as Reactive Airways Dysfunction Syndrome (RADS).^(38,39)

Within the SENSOR case classification scheme, WAA is defined as work-related exacerbations of a preexisting asthma condition. Workers with a history of symptomatic or treated asthma within the past 2 years and who have an increase in symptoms or use of asthma medications are classified as having work-aggravated asthma.^(38,39) Workers with no history of asthma or with preexisting asthma who have been asymptomatic for the past 2 years (e.g., childhood asthma) are considered to have new-onset asthma. NOA refers to sensitizer- or irritant-induced asthma caused by agents that may or may not be previously documented (known) in the medical literature as causes of occupational asthma.

RADS refers to new-onset persistent asthma resulting from a one-time high-dose irritant exposure.⁽³⁹⁾ The agent(s) that caused the asthma is (are) described by the injured worker during the surveillance interview, and is (are) coded using the Association of Occupational and Environmental Clinics (AOEC) exposure code list.⁽⁴⁰⁾ Isocyanates, as an agent, can result in either airway sensitization or act as a respiratory irritant. For cases in which an interview cannot be obtained, medical records that sometimes include Material Safety Data Sheets (MSDS) may be used to code the agent(s) involved in the exposure.

To gain further insight into the isocyanate-induced asthma cases, surveillance interviews and medical records were reviewed by one of the authors and also by a research analyst. Additionally, information to answer the following yes/no questions was sought: 1) if a spray application, was the item large, awkwardly shaped, or a fixed outdoor structure?, and 2) did the injured worker directly handle isocyanates? When an injured worker reported during the surveillance interview or in the medical records that dermal exposure to isocyanates was a factor contributing to his or her asthma, this was noted. These questions were answered in relation to the predominant task performed, or if emergency care was sought, to the task being performed at the time of respiratory distress.

Claim costs for self-insured workers were excluded from the cost summary because these claims have incomplete cost records in the L&I's Workers' Compensation database and cannot be accurately estimated. For State Fund workers' compensation claims the costs presented are based on all costs paid to date for closed claims. For claims that were still active and open (n = 3) on the date of extraction (Dec. 15, 2011), the claim costs represent those costs paid to date as well as an estimate of future expected claim costs. Future expected claim costs are estimated by the workers' compensation case reserve unit. Reserves are based on an experienced claim adjudicator's best estimations of claim costs for the life of the claim. If appropriate, reserves are estimated for medical care by injury type, wage costs, vocational rehabilitation costs, permanent partial disability, pension, and other claim costs. Costs are not adjusted for inflation.

Claims are defined as compensable if they meet a 3-day waiting period for time loss compensation and are further classified as “compensable,” “kept-on-salary,” “total permanent disability,” “fatal,” or “loss of earning power.” Time loss payments occur over time and in some cases may extend over several years. Both compensable and medical-only (non-compensable) claims from the State Fund are included in this analysis. The indirect cost to employers (e.g., employee turnover, productivity loss, and poor employee morale), the indirect costs to workers, and the administrative costs of managing the claims are not included in the claim costs. The Kruskal-Wallis non-parametric rank test was used to compare the median costs of isocyanate-induced asthma cases with all other asthma cases.

First, the observation of respiratory disease associated with large-object spraying is supported by exposure assessment conducted by Janko et al.⁽⁴¹⁾ Janko et al. evaluated isocyanate exposures in three categories of spray finishing: continuous spray finishing, auto body repair, and large object spray operations in which the capacity of the spray facility was frequently exceeded by the size and unusual shape of the object being painted.⁽⁴¹⁾ The highest exposures to HDI polyisocyanates (HDI_p) were documented during spray painting of large objects such as coaches (buses), boats, and horse trailers.⁽⁴¹⁾ The geometric means (GM) for HDI_p during large-object spraying ranged from 2 to 16 mg/m³ with a peak of 30 mg/m³; this exceeds the Oregon Occupational Safety and Health Administration (OSHA) short-term exposure limit (STEL) of 1 mg/m³ for HDI_p by a large margin. Two contributing factors in the high exposures documented by Janko et al. are: a) the inherent difficulty in ventilating large or outdoor objects and b) team spraying, in which more than one painter is simultaneously generating isocyanate exposure.⁽⁴¹⁾ Fifty percent (n = 9) of the respiratory disease cases presented here for painting and coating processes were associated with large, awkward, or fixed outdoor objects that are difficult to ventilate. The propensity of illness described here is in agreement with Janko et al.'s documentation of high airborne isocyanate exposures from the painting of large and awkward-shaped objects.⁽⁴¹⁾

Second, six cases document new-onset asthma to isocyanates from indirect exposure. Three of the cases involve injured workers who typically might not be enrolled in an employer's respiratory protection program such as forklift driver, equipment technician, and automotive office manager. Two additional cases occurred in workers who were not spraying isocyanate product directly, but were indirectly exposed while assisting lead sprayers. Half of the indirect-exposure cases occurred from exposure to MDI associated with the manufacturing of MDI-based foam. The observation of indirect exposure underscores the importance of: a) isocyanate source control, particularly for MDI-based manufacturing processes and b) the use of ventilation and respiratory protection for assistants working in close proximity to an isocyanate application.

The third observation relates to two cases presented here in which injured workers were exposed to isocyanates during secondary tasks (such as cleanup) and reported dermal exposure as contributing to their symptoms. There is evidence from animal toxicity studies^(23,24,42) as well as limited human data,^(19,21,22) that dermal exposure to isocyanates can lead to systemic respiratory sensitization. In a few limited epidemiological studies, isocyanate skin exposure^(27,28) and not wearing gloves when handling isocyanates⁽²⁶⁾ have been associated with asthma symptoms in some workers. Petsonk et al. described an association between skin exposure during spill cleanup and the cleanup of an MDI blender in a wood products plant and asthma-like symptoms in the workers performing those tasks.⁽²⁷⁾ Petsonk et al.'s observations are similar to the cleanup tasks reported here for handling empty storage containers and unmasking of vehicles after spray painting.⁽²⁷⁾ Heederick et al. conducted a comprehensive literature search on primary prevention for occupational asthma and concluded that published case reports and cross-sectional studies provide “limited” evidence that skin exposure contributes to the onset of occupational sensitization and asthma.⁽²⁰⁾

Limiting dermal exposure to isocyanates is a prudent approach in the prevention isocyanate-induced asthma.^(19,20) The surveillance cases presented here highlight a challenge for limiting dermal exposure: while employers may recognize and control isocyanate exposures during the primary task, exposure during secondary tasks may be under-recognized and the importance of dermal protection throughout all tasks needs to be stressed. Selecting appropriate dermal protection in the workplace can be difficult, however, because most glove and coverall manufactures do not provide information specific to protection from isocyanates. The U.S. Environmental Protection Agency (EPA) recommends nitrile gloves when handling isocyanates.⁽⁴³⁾ Ceballos et al. have shown that while latex is not protective, butyl rubber and thicker (>8 ml) nitrile materials do provide some protection from the isocyanates present in automotive paint formulations.⁽⁴⁴⁾

Two cases reported here involve work processes not commonly associated with occupational asthma. The first involved the use of an MDI-based sealant in insulated glass manufacturing. The production worker (case 19), who had 31 years experience at the facility, experienced respiratory irritation within 30 days of using the MDI-based sealant during window production. The worker's respiratory symptoms resolved when the worker was retrained into the facility's service department. The second processes (case 3) involved the application of an MDI-based protection liner (similar to truck bed liners) inside a city sewer pipe. The worker developed new-onset asthma from indirect exposure as a line tender working inside the pipe during the liner application. The purpose of installing the isocyanate-based liner was to prevent corrosion and to extend the service life of the sewer pipe.

The majority of cases reported here are for exposure to processes that are similar to other cases previously reported. The most common work process presented here is exposure to automotive paints, a process that is well known to cause respiratory disease,^(8,45,46) and that has been associated with two fatalities.^(33,34) One of the indirect exposures presented here was for an automotive manager in a collision repair setting, and the case is similar to an indirectly exposed automotive secretary with hypersensitivity pneumonitis (HP), reported by Schreiber et al.⁽⁹⁾ High airborne exposure to MDI during truck bed lining application has been previously reported in Washington and we report two cases of asthma in truck bed applicators.⁽⁴⁷⁾

Exposure to isocyanates during foam manufacturing is well known to be associated with respiratory illness,^(10,12,48), and one fatality⁽³⁰⁾; we present two cases of asthma in foam manufacturing here. Two additional foam cases are presented, both associated with spray foam used as a stabilizer in the shipment of mechanical instruments. The development of asthma by two home occupants (non-occupational exposure) following the installation of spray polyurethane foam insulation in a residential attic has been recently reported,⁽⁴⁹⁾ and we document occupational asthma in a foam insulation assistant here. An MDI-based resin system for making molds in the manufacture of synthetic rocks is also reported here, similar to a fatality reported by Carino et al. for a MDI-exposed worker in a steel foundry using mold and core processing.⁽²⁹⁾

Regarding isocyanate exposure in workplaces overall, there are industrial processes associated with isocyanate-induced respiratory illness that are not reported here. In the wood products industry for example, isocyanate exposure in wood-chip board manufacturing⁽¹⁵⁾ and in composite and synthetic wood product manufacturing^(27,50) is associated with respiratory illness. In health care, isocyanate asthma has been reported in a nurse handling plaster casts and isocyanates as irritants have been reported in orthopedic nurses working with soft casts.^(16,51) While these industries have reported non-isocyanate (i.e., cleaning chemicals, mold, and so on) asthma into Washington's asthma surveillance program,⁽⁷⁾ no cases of isocyanate-induced asthma were reported from these industries to date, but cases could be reported in the future.

Isocyanate-exposed workers reported using all types of respiratory protection, from dust masks through supplied air systems (Table III). The value of the respiratory protection documented in workers' compensation claims is limited because the respirator's Assigned Protection Factor (APF), cartridge type, and consistency of use cannot be discerned with sufficient detail. Nonetheless, review of these cases raises two useful observations. The first observation concerns laborers assisting lead sprayers in enclosed spaces, such as attics and sewer pipes (cases 12 and 3). In both of these cases, the assistants were not provided the same level of respiratory protection as the leads, despite working in very close proximity to the exposure. To prevent these types of cases elsewhere, product vendors and employers need education on the potential toxicity not just to the spray operator, but for all workers in the vicinity of product application, particularly in enclosed spaces.

The second observation is tied to the association of asthma from exposure to painting large objects that are difficult to ventilate. While there is evidence that respiratory protection can reduce isocyanate exposure in spray operations,^(52–54) unfortunately there is little direct evidence in the literature on respirator effectiveness in the primary prevention of respiratory disease.⁽²⁰⁾ Several of the exposure scenarios presented here are outside of the manufacturing setting, are difficult to effectively ventilate, and therefore rely on effective respiratory protection programs. The effectiveness of respiratory protection programs to prevent asthma in these settings is currently not well understood, and this is an opportunity for further research.

The substitution of isocyanates with less hazardous chemicals could reduce the risk of respiratory illness and is the preferred hierarchy of control. The development, testing, and adoption of isocyanate-free formulations is currently limited and varies among the many processes and products that utilize isocyanates. Toxicity testing and health evaluation of isocyanate-free products are needed to establish the safety of new chemical formulations; this is an area in need of further research and development.