Investigation of determinants of past and current exposures to formaldehyde in the reconstituted wood panel industry in Quebec.

Objectives: Past and present formaldehyde measurements made in facilities manufacturing reconstituted wood panels in Quebec have been collected in order to assess formaldehyde exposure and its determinants in this industry.

Methods: All 12 plants manufacturing Oriented-strand board (OSB), Medium density fibreboard (MDF) and Particle board (PB) in Quebec were visited by a research team which took area and personal measurements. Past measurements taken by governmental occupational health teams in these plants were also collected. Log-transformed formaldehyde concentrations were analysed with extended linear mixed-effects models.

Results: During 2001-2002, 275 measurements were taken by the research team, while 590 measurements dating back to 1984 were collected from governmental files. The area measurements had a global geometric mean (GM) of 0.28 p.p.m. [geometric standard deviation (GSD): 3.1]. The GM of the personal measurements was 0.17 p.p.m. (GSD: 2.3). The fixed-effects of the models for personal and area measurements explained 61 and 57% of the variance, respectively. Job (working area for area concentrations), process (PB, MDF, OSB), season of sampling, origin of the data (research, governmental) and year of sampling were significant determinants of exposure. Proximity to the press, winter conditions, PB and MDF processes and governmental data resulted in the highest exposures. Significant within-sampling campaign correlation was found for both personal and area models. The final models include different residual variances by process for personal measurements and by working area for area measurements.

Conclusions: Several determinants of exposure to formaldehyde in the reconstituted wood panel industry were successfully identified. Higher levels found in governmental data as compared to research data may be explained by a 'worst-case' strategy bias. The observed intra-sampling campaign correlation supports existing results suggesting that measurements taken in a small time frame tend to be correlated. Exposures in this sector are low compared to most 8 h-TWA occupational exposure limits (e.g. 1 p.p.m.) but close to the most demanding ones (e.g. 0.3 p.p.m.).