4,4'-methylenediphenyl diisocyanate

Epidemiological data

Administrative data

Endpoint:

epidemiological data

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

2011

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Expert review of available data.

Data source

Reference

Reference Type:

publication

Title:

Reduction in Diisocyanate and Non-Diisocyanate Sensitizer-Induced Occupational Asthma in Ontario

Author:

Buyantseva LV, Liss GM, Ribeiro M, Manno M, Luce CE and Tarlo SM

Year:

2011

Bibliographic source:

J. Occup & Environ. Med. Vol. 53, P420-426.

Materials and methods

Study type:

cohort study (retrospective)

Endpoint addressed:

respiratory sensitisation

Principles of method if other than guideline:

Records were abstracted from the Ontario Workplace Safety and Insurance Board using methodology similar to their previous investigation that had looked at claims/year during 1980 to 1993.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

9016-87-9

Cas Number:

9016-87-9

IUPAC Name:

9016-87-9

Details on test material:

Commercial diisocyanates of all types are included in this review.

Method

Type of population:

occupational

Ethical approval:

confirmed, but no further information available

Details on study design:

For this study, the protocol was reviewed and approved by the Research Ethics Board of the University of Toronto. The Ontario Workplace Safety and Insurance Board (WSIB) occupational disease database was searched for claims that contained primary diseases that included asthma and/or reactive airways dysfunction syndrome (RADS). The other detailed search criterion set by WSIB which was necessary for this study included recorded “date of accident”, which had to be between January, 1998, and December, 2002 (five consecutive years). Any claimant who did not clearly fit into set categories or had discrepancies between the WSIB and treating physicians’ diagnosis was reviewed by two physicians experienced in occupational lung diseases (S.M.T. and G.M.L.). The final categorization was reached by consensus of the two reviewing specialists.

Exposure assessment:

estimated

Statistical methods:

Data analyses were performed in SAS, version 9.1 (SAS Institute, Cary, NC). The outcome variables are expressed as crude rates of prevalence.. Comparisons of continuous and categorical variables were conducted via two-tailed t test (Wilcoxon ranked sum test for nonparametric analysis) and chi-square tests (Fisher exact test when appropriate), respectively.

Results and discussion

Results:

In the sensitiser-induced OA claims, a minority was attributable to ISO, 37 cases (37.4%) and 62 cases (62.6%) were N-ISO, resulting in an ISO/N-ISO ratio of 0.6 and average yearly allowed claims rate of 7.4 and 12.4, respectively. Occupational asthma claims were classified as definite in 50% (15 ISO and 34 N-ISO claims), probable in 10% (5 ISO and 5N-ISO claims) and possible in 40% (17 ISO and 23 N-ISO claims). Compare to the previous report spanning 1980 to 1993, 425 claims were in the ISO group and 419 were in the N-ISO, for the ratio of 1.01 and average yearly claims rates of 30.4 and 29.9, respectively. The changes in relative distribution between ISO and N-ISO claims between the prior and the current observation periods were statistically significant (P = 0.0094). In comparison of demographics and other characteristics between the ISO and N-ISO OA groups showed no significant differences, except for a greater percentage of males in the ISO group (86% vs 60%, P = 0.01). The mean time between the onset of symptoms and the final diagnosis was similar for both ISO and N-ISO groups. At the time of the main medical assessment, a similar fraction of workers remained exposed to the suspected culprit agent at work: 30% of the ISO group and 31% of the N-ISO group. The groups were also similar in composition of smokers, family history of asthma, and history of childhood asthma. Among the entire OA sample, only 9 (9%) had an occupational laboratory challenge, confirming the diagnosis in 3. Those 6 claims with a negative occupational laboratory challenge test had other findings that supported the diagnosis of OA and led to inclusion with the diagnostic criteria for this report.

In the ISO group, there were 22 (59.4%) cases with only one potential sensitizing exposure agent identified in the file, 13 (35.2%) cases with two possible implicated exposure agents (such as amines, epoxy compounds, acrylates), and 2 cases (5.4%) with three possible implicated exposure agents. The type of ISO agent was specified in the file in only 16 cases (43%): toluene diisocyanate in 5, methylene diphenyl diisocyanate in 5, and hexamethylene diisocyanate in 6.

A majority in both groups reported at least an improvement in respiratory symptoms at the last assessment; and although not statistically significant, a greater proportion of the ISO group reported clearing of all of their symptoms (46% of the ISO group vs 27% of the N-ISO group).

Applicant's summary and conclusion

Conclusions:

In conclusion, the study reports a reduction in absolute number of diisocyanate-related occupational asthma allowed claims in Ontario, Canada. Nearly half of the diisocyanate related cases ultimately became fully cleared of symptoms. Their authors conclude that the surveillance program aimed at reducing ISO OA frequency had a positive impact.

Executive summary:

The objective of this study was to investigate relative frequency and features of diisocyanate (ISO) and non-diisocyanate (N-ISO) occupational asthma (OA) claims allowed in Ontario, Canada, during a 5-year period (1998 to 2002). Records were abstracted from the Ontario Workplace Safety and Insurance Board using methodology similar to their previous study evaluating claims between 1980 and 1993. .

The ISO group had more males (86% vs 69%, p=0.01), but there were no other significant differences. The most common professions were spray painters (41%) and production workers (38%) in the ISO group and production workers (49%) and health care workers (8%) in the N-ISO group. The current study reported 7.4 ISO claims/yr a significant decrease when compared to 30 ISO claims/yr during 1980 to 1993 .

 

A majority in both groups reported at least an improvement in respiratory symptoms at their last assessment; and, although not statistically significant, a greater proportion of the ISO group reported clearing of all of their symptoms (46% of the ISO group vs 27% of the N-ISO group). Study authors suggested that ISO claims declined from the previous period perhaps because of effective surveillance programs.