Article Text

Surveillance of mesothelioma and workers' compensation in British Columbia, Canada
1. Tracy L Kirkham1,
2. Mieke W Koehoorn1,2,3,
3. Christopher B McLeod2,3,
4. Paul A Demers1,2
1. 1School of Environmental Health, The University of British Columbia, Vancouver, British Columbia, Canada
2. 2School of Population and Public Health, The University of British Columbia, Vancouver, British Columbia, Canada
3. 3Centre for Health Services and Policy Research, The University of British Columbia, Vancouver, British Columbia, Canada
1. Correspondence to Dr Mieke W Koehoorn, School of Population and Public Health, University of British Columbia (Rm 289) 2206 East Mall, Vancouver, BC V6T 1Z3, Canada; mieke{at}interchange.ubc.ca

## Abstract

Objectives To determine the rate of workers' compensation for mesothelioma cases in the Canadian province of British Columbia, examine trends in mesothelioma cases and compensation over time, and identify factors associated with compensation status for mesothelioma cases.

Methods Mesothelioma cases in the provincial cancer registry were linked at the individual level with accepted claims for mesothelioma in the provincial workers' compensation system for the period 1970–2005.

Results 391 of the 485 workers' compensated claims were linked (81% match rate) with a record in the cancer registry for an overall mesothelioma compensation rate of 33% over the study period and a high of 49% in the last 5 years. Compensation rates were lower for women, older (retired) as well as younger workers, and sites other than the pleura.

Conclusions Although the workers' compensation rate for mesothelioma increased over time, the rate was much lower than anticipated for cases believed to be work-related cancers. Several key factors may significantly influence awareness by clinicians and workers of the work-relatedness of mesothelioma and of workers' compensation benefits. Regulatory agencies need to develop policies or effective notification systems to ensure that all newly diagnosed mesothelioma cases seek compensation benefits.

• Mesothelioma
• occupational diseases
• population surveillance
• workers'
• compensation
• health surveillance

## Introduction

Mesothelioma is a rare aggressive cancer of the mesothelium, the protective lining of the body's internal organs, that is almost always fatal.1 The incidence of mesothelioma has been increasing among males and females worldwide due to asbestos exposure.2–7 The peak of mesothelioma cases is predicted to occur sometime between 2001 and 2015, and is not expected to reach background levels until approximately 2050, although the pattern varies across countries due to differences in asbestos usage.2 5

Asbestos exposure is considered the primary cause of mesothelioma, and the global use of asbestos and the incidence of mesothelioma are positively associated.8 The attributable risk for mesothelioma ranges from 74% to 88% for known asbestos exposure.9–12 Asbestos exposure is typically from occupational sources and mesothelioma is recognised as a compensable occupational disease in many countries including Canada. Generally, 85–90% of mesothelioma among men and 20–30% among women is assumed to be due to occupational exposure.10 13 Accepted compensation claims for mesothelioma have been steadily increasing in Canada, where the number of claims has more than doubled in several provinces since the 1970s.4 14 15 For example, in Ontario the number of accepted claims increased from 10 per year in the 1960s to over 50 per year in the 2000s.15 Mesothelioma is also associated with non-occupational exposure related to residential proximity to mines and industrial facilities, residential insulation, and family members being asbestos workers.16–18

Although mesothelioma is recognised as an occupational disease, workers' compensation rates are lower than expected for the cases attributable to occupational exposures. Research in France found only 62% of cases covered for compensation benefits submitted a workers' compensation claim for malignant mesothelioma and 40% of cases who did not apply for compensation had a known asbestos exposure.9 In New South Wales, Australia, 64.6% of mesothelioma cases reported to the cancer registry from 1972 to 2004 were compensated by the workers' compensation system.19 It is thought that few submitted claims for mesothelioma are rejected or denied for compensation, suggesting that the low compensation rates are due to cases not seeking compensation. In the Canadian province of Ontario for example, 38% of pleural and peritoneal mesothelioma cases between 1980 and 2002 filed for compensation and 87% received it for an overall compensation rate of approximately 33%.20

Little is known about the factors associated with workers' compensation for mesothelioma. Information on the compensation of mesothelioma cases and the characteristics of those who do not seek compensation are needed to help guide policy development to ensure those who are eligible apply for workers' compensation benefits. The aim of this study was to (1) determine the compensation rate of mesothelioma in the Canadian province of British Columbia (BC), (2) examine trends in mesothelioma cases and compensation over time, and (3) identify factors associated with receiving compensation for mesothelioma in BC.

## Methods

This study involved the linkage, at the individual level, of all mesothelioma claims from the provincial workers' compensation system and all histology-confirmed mesothelioma cases from the provincial cancer registry for the period 1970–2005. All claims and cases were extracted based on claim registration date and diagnosis date, respectively.

The BC Cancer Agency (BCCA) maintains a provincial tumour registry that collects histological, personal and demographic data on all newly diagnosed cancers in the province of BC. This includes pathological diagnoses from hospitals, clinics and cancers identified on death certificates. The registry is considered comprehensive for the provincial population. WorkSafeBC, the provincial workers' compensation system, maintains a database of accepted short-term disability (time loss), long-term disability (permanent disability) and fatal claims for work-related injury, illness and disease occurring in BC workplaces. WorkSafeBC covers over 90% of the provincial workforce.

All mesothelioma cases diagnosed between 1970 and 2005 were requested from the BCCA tumour registry using histology codes (ICD-O-3 code 905). Extracted records included data on sex, age, age at diagnosis, geographical location, year of diagnosis and cancer site. All accepted workers' compensation claims for mesothelioma were requested from WorkSafeBC. Demographic and work data obtained for all claims included sex, age, time of claim, location at time of claim, source of injury, ICD-9 medical diagnosis, disease outcome, occupation or industry of employment at time of diagnosis and geographical health region. For our study both health authority and health service delivery area were used to identify geographical location. The five regional health authorities in BC are responsible for funding and delivering a wide spectrum of healthcare services to their populations. Each health authority is divided into three or four health service delivery areas that are used for reporting and for health services planning and delivery.

Linkage of the workers' compensation claims to the tumour registry cases at the individual level was conducted by personnel at the BCCA using personal health numbers (unique identifiers), or where health numbers were not available, by a combination of full name, sex, birth date and postal code at time of diagnosis/claim registration. Relaxing the criteria for linkage purposes (ie, last name and month and year of birth only) did not improve the success rate. The linked database was provided to the research team with personal identifiers removed from the database and replaced with an anonymous study identifier. These procedures were governed by a data agreement between the researchers and both the BCCA and WorkSafeBC, and approved by the Behavioural Research Ethics Board at the University of British Columbia (certificate number B04-0626).

### Statistical analysis

All analyses were performed with Stata 9.2.21 Basic characteristics of the study population were calculated by compensation status. Compensated cases are those with an accepted workers' compensation claim in BC and non-compensated cases are those who did not receive compensation benefits in BC, regardless of eligibility or whether or not they applied for compensation. A claim may be rejected if there was no occupational history in BC and a claim may be disallowed if adjudication is unable to identify any occupational exposure to asbestos. Nevertheless, almost all mesothelioma cases presented to WorkSafeBC for compensation are accepted (T Bogyo, personal communication, 2008). Unadjusted and adjusted logistic regression models were used to determine the associations between compensation for mesothelioma and socio-demographic, geographical and histological characteristics, with the odds of being a non-compensated case being modelled. Robust standard errors were calculated to account for departures from assumptions underlying the standard logistic regression model.22 For all analyses confidence limits of 95% were used as the level of significance.

## Results

A total of 1182 mesothelioma cases were identified in the cancer registry and 485 mesothelioma cases were identified from workers' compensation claims for the period 1970–2005. Of the 485 compensated claims, 391 were linked (81% match rate) with a record in the cancer registry for an overall mesothelioma compensation rate of 33% over the study period. Almost two thirds were matched using the unique provincial health number, with the remainder being matched through a combination of last name and birth date or first name. Unmatched claims were on average younger (54 years vs 65 years old) at the time of diagnosis and less likely to be female (2.1% vs 3.3%) than matched claims.

Figure 1 illustrates the number of mesothelioma cases as identified by the cancer registry and the proportion of those cases with a workers' compensation claim for each year between 1970 and 2005. The numbers of mesothelioma cases have increased over time, with the highest number of cases (n=77) diagnosed in 2001. Following 2001 the number of cases appears to have reached a plateau. The proportion of cases with a workers' compensation claim (ie, compensation rate) also increased over time, with a peak compensation rate of 49% in 1999 and in 2004.

Figure 1

Mesothelioma cases (black) diagnosed in British Columbia from 1970 to 2005 and the number of those cases compensated (grey) by workers' compensation. BCCA, BC Cancer Agency.

Table 1 shows the distribution of study characteristics among the mesothelioma cases by compensation status. Non-compensated cases (n=791) tended to be older on average than compensated cases (67.6 vs 65.3 years old) and to have greater variability with ages ranging from 14-104 years of age compared to 36–88 years of age among those who received compensation. The compensation rate was higher for males (37.9%) compared to females (6.6%), for those aged 55–64 at diagnosis (45.5%) compared to other ages (29.2%) and for those with mesothelioma of the pleura (36.6%) compared to other sites (12.6%). Compensation rates ranged from a high of 76.5% to a low of 25.8% across different health regions (figure 2), with densely populated urban areas tending to have lower compensation rates compared to northern and/or rural areas.

Table 1

Mesothelioma case characteristics by compensation status

Figure 2

Geographical variation of compensation rates by health service delivery area and health authority, 1970–2005.

Table 2 presents the results of the multiple logistic regression model of factors associated with compensation status for mesothelioma. Women were eight times more likely than men to be a non-compensated mesothelioma case. Younger and older individuals, compared to those aged 55–64, were more likely to be a non-compensated case. In particular, those age 75 years of age and older were four times more likely to be a non-compensated mesothelioma case than those aged 55–64. Those with mesothelioma of the peritoneum and other sites were approximately 5.5 times more likely to be a non-compensated case compared to those with mesothelioma of the pleura. Those with mesothelioma attributed to the lung also had an elevated odds of not receiving compensation benefits, although the 95% CI included ‘1’ for this cancer site. Mesotheliomas cannot arise in lung tissue, so these are either site coding errors or, possibly, histological coding errors. The latter is less likely because of microscopic confirmation of histology.

Table 2

Adjusted logistic regression showing ORs and 95% CIs of not having a workers' compensation claim for mesothelioma (n=1053)

In simple logistic regression the odds of being a non-compensated mesothelioma case was elevated for those diagnosed during the 1970s and the 1980s compared to those diagnosed in the 1990s and later (OR 3.56 and 1.46, respectively). This effect was not seen in the final model adjusted for socio-demographic and clinical characteristics.

Differences in the compensation status of mesothelioma cases were found by geography, defined by health service delivery areas in this study. Mesothelioma cases living in the Kootenay Boundary health service delivery area at the time of their diagnosis were almost twice as likely to be a compensated mesothelioma case as those who lived in the Okanagan, the health service delivery area that had the lowest rate of compensation.

Among the compensated mesothelioma cases, the majority of workers were employed in the manufacturing, construction and service sectors (77.2% of compensated cases). Only small differences in the distribution of compensated claims by industry were noted for cancer registry status (table 3).

Table 3

Comparison of industry type reported as industry at time of exposure of accepted mesothelioma claims by BC Cancer Agency (BCCA) status

## Discussion

The overall compensation rate for mesothelioma in BC from 1970 to 2005 was 33%, but slowly increased over the study period. The compensation rates are much lower than anticipated for cases believed to be work-related. They are also much lower than those reported for both France and Australia, but similar to that reported for Ontario, Canada.9 19 20 Gender, cancer site, age at diagnosis and geographical location were all associated with compensation status for mesothelioma in BC.

In our study, we assumed that the non-compensated mesothelioma cases were individuals who did not submit a claim for workers' compensation benefits. Few claims for mesothelioma in BC are rejected or disallowed (T Bogyo, personal communication, 2008). This is supported by other studies. In France, 91% of submitted claims were accepted and in Ontario 87% were accepted.9 20

The increase in mesothelioma cases we observed, and potential peak in 2001, is similar to patterns reported in the USA, Europe and Ontario.2–7 The observed drop in the compensation rate in 2005 in our study may be due to the lag between diagnosis, claim registration and claim acceptance dates. A reanalysis of the data with a more recent data extract, however, found similar levels of compensation in 2005.

Women were eight times more likely to be a non-compensated mesothelioma case than men. One possibility is that some women may develop mesothelioma due to residential exposure and, as such, are not eligible for workers' compensation.17 One form of residential exposure that may be more common among women is secondhand exposure to asbestos in the home via family members with occupational exposures. A recent study conducted in Australia showed that women had a non-significant increased risk (HRR 2.67 and 2.61) of developing mesothelioma if they lived with, or washed the clothes of, someone who worked for the Australian Blue Asbestos Company.23 Similarly, Spirtas et al reported attributable fractions of 7.9% for mesothelioma cases among women if their cohabitant had ever been exposed to asbestos.11 Historically, given a potential 30-year lag for exposure and disease, the observed pattern of a lower compensation rate for women could also reflect working patterns and gender differences in exposure for men and women. While this may account for some of the decreased compensation rates, our reported 6.6% compensation rate among females, comparable to that reported in New South Wales (5%), is still below the 20–30% of mesothelioma cancers among women thought to be work-related.10 19

An alternative explanation for the decreased compensation rate among women may be that both diagnosed women and their physicians do not recognise this as an occupational disease for women. Mesothelioma has largely and historically been attributed to industrial exposures associated with male dominated work environments, such as asbestos mines or manufacturing. Less well understood is the possibility of exposure for women working in support roles in industrial settings with asbestos exposures or near construction activities in workplaces that resulted in unknown asbestos exposure (ie, school buildings, administration offices).

Non-compensated mesothelioma cases were more likely to occur among the older age groups. Retired workers (typically those over the age of 65 years) may be less likely to make the connection that their cancer is work-related or their clinicians to probe about historical workplace exposures once a worker leaves the workforce. Both workers and clinicians may also not be aware that retired workers are still eligible for some compensation benefits. Regulatory agencies need to develop education campaigns or effective notification systems to ensure that all newly diagnosed mesothelioma cases seek compensation benefits, regardless of current work status.

Site of cancer may be an important factor as to whether a person seeks compensation for mesothelioma. We found that mesotheliomas of the lung, peritoneum and other sites were 2.3, 5.4 and 5.5 times less likely to be compensated than mesothelioma of the pleura. This may be due to familiarity with the association between asbestos exposure and cancer of the pleura, more so than other sites, among clinicians who in turn may be instrumental in encouraging individuals to seek compensation for work-related disease.

Lastly, we found that compensation rates vary by the region of the province, ranging from 76.5% to 25.8%, where more urban areas received lower compensation rates than non-urban regions that may include some communities with natural resource-based industries. The reasons for the observed variation are unknown. We speculate that public knowledge in areas with large industrial settings and known exposures to asbestos may influence the awareness of compensation claim benefits among both the workers and the physicians in the area. Goldberg et al also reported a significant variation in the proportion of subjects who submitted claims by region (13–46%).9 Another study found the variation in compensation rates by geography was greater than in our study (5% to 61.5%) when looking at only mesothelioma of the pleura among men.24 They reported this effect was not associated with asbestos exposure and was most likely due to “physicians' sensitisation to the issue, and/or the patient's decision”, supporting our assumption.

The low compensation rate for mesothelioma is an important public health and compensation issue for several reasons. First, workers with an occupational disease deserve compensation. Second, employers pay insurance premiums for these situations and these premiums are affected by the current rates of claims. In many other circumstances, increased premiums may encourage employers to invest resources into reducing exposure to help curb future costs. This is unlikely for mesothelioma due to the long latency period between disease and exposure (30–40 years). However, it may help increase awareness of the disease and the occupational attributable risk. Third, medical costs associated with the mesothelioma cases that are not compensated are paid for by the Canadian public healthcare system, funded through general tax revenue, rather than employer premiums. This cost shifting increases the financial burden on the public healthcare system. The effect of cost shifting may be less of a policy concern in healthcare systems that have a different financing structure. Workers' compensation provides other medical care and benefits that would otherwise be the responsibility of the patients themselves who are not covered by the public system. These services may include hospice care, medications, alternative treatments, medical equipment and associated transportation and lodging expenses. Further, claims can be awarded death benefits (ie, cost of funeral) and survivor benefits for the families. Leigh and Robbins estimated that in 1999, US$8 to US$23 billion in medical costs were shifted from workers' compensation to taxpayers, private medical insurance and workers and their families for uncompensated occupational deaths and diseases.25 This signifies a large economic burden on individuals or their families who do not receive compensation.

Although restricted by the data available for this study, there were other factors that may influence a worker's choice to submit a claim for compensation benefits for which we did not have data such as social or economic status, support status, awareness of the disease, and occupation or industry. Occupation or industry may have a significant impact on a worker's choice to submit a claim. It would have been beneficial to be able to compare occupation information by compensation status. We did have industry sector and occupational codes for compensated cases, but these data are not recorded in the cancer registry for tumour cases.

The compensation rate(s) we reported may have been influenced by misclassification. In Canada, workers' compensation is a provincial jurisdiction and compensation claims are ultimately administered by the provincial system where exposure took place, regardless of where someone is currently living. Some non-compensated cancer cases in the BC cancer registry may have received workers' compensation from another province where their occupational exposure occurred. We did not have access or linkage to compensation claims from other provincial jurisdictions. Further, 94 of the 485 compensation claims were unmatched to the cancer registry and may be explained as individuals with an occupational exposure in BC (ie, claim is registered in BC) but who currently reside elsewhere. Future work looking for these cases in other provincial cancer registries may prove informative. If we were able to match all of the 485 workers' compensation claims, the compensation rate for mesothelioma cases would have reached 41%, which is still below the percentage expected to be work-related and compensated.

An additional limitation of our study was missing data. We had 129 cases missing geographical location, reducing our study sample for the multiple logistic regression model to 1053 cases. All cases were included in the overall compensation rate analysis. In addition to this, geographical location had 16 categories, some of which had few cases. This most likely widened our confidence limits, thereby decreasing our chances of detecting a statistically significant difference.

The results from this study can help guide policies and programs that will increase the proportion of mesothelioma patients that seek and, if eligible, receive workers' compensation. In 2005 the BCCA and WorkSafeBC implemented a strategy to increase awareness of workers' compensation benefits for mesothelioma. Physicians for all mesothelioma cases in the cancer registry were mailed a letter prompting them to inform their patients of mesothelioma as an occupational disease and to enquire about workers' compensation benefits. Phase II of this study will evaluate the effect of the physician intervention letter on (1) the claim rate, and (2) on time to claim. Further, investigation of disallowed and rejected workers' compensation claims will be ascertained to confirm the assumption that uncompensated cases are primarily due to workers not seeking compensation rather than being rejected.

The results of this research indicate that mesothelioma is compensated at much lower levels than anticipated for all work-related cases, and that women, the young and old, those with cancer sites other than the pleura, and those diagnosed in more urban environments are less likely to be compensated and/or seek compensation benefits. The identification of these factors can be used to develop effective policies to ensure that people who may be eligible for compensation benefits do seek them.

• Mesothelioma is a cancer almost entirely attributable to occupationally-related asbestos exposure.

• Mesothelioma cases and compensation rates for mesothelioma are increasing over time. Workers' compensation rates are much lower than anticipated for cases believed to be work-related cancers.

• Gender, age at diagnosis, geography, and cancer site are factors that influence the likelihood of an individual with mesothelioma seeking and receiving compensation.

• Low compensation rates may be placing a large economic burden on public healthcare systems, and on the individual families of those with mesothelioma.

• Regulatory and public health agencies need effective notification systems to ensure that all individuals newly diagnosed with mesothelioma seek compensation benefits.

## Acknowledgments

The authors thank Lillian Tamburic for programming assistance and Dawn Mooney for cartographic assistance.

## Footnotes

• Funding This research was funded by WorkSafeBC (the Workers' Compensation Board of British Columbia) through the WorkSafeBC-CHSPR Research Partnership. Dr Koehoorn was supported in part by a Michael Smith Foundation for Health Research Senior Scholar Award. Tracy Kirkham was supported by a Canadian Institutes of Health Research—Institute of Population and Public Health/Public Health Agency of Canada Doctoral Research Award and a Michael Smith Foundation for Health Research/WorkSafeBC Senior Trainee Award.

• Competing interests None.

• Ethics approval Ethics approval was granted by the Behavioural Research Ethics Board at the University of British Columbia (certificate number B04-0626).

• Provenance and peer review Not commissioned; externally peer reviewed.

## Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.