A comparison of engineering controls for formaldehyde exposure during grossing activities in health care anatomic pathology laboratories

ABSTRACT

This article for the first time reports a large set of monitoring results for formaldehyde exposure during grossing activities in health care anatomic pathology laboratories, and compares the effectiveness of different local exhaust ventilation systems on the exposure. To control the confounding effects from grossing work load, sampling duration, and the sizes of specimens grossed, only 15-min short-term personal exposure samples collected during large tissue specimen grossing were used for the comparison of the effectiveness of these local exhaust systems. While we also collected long-term 8-hr time weighted average samples, these are not treated in this analysis. The systems examined were canopy receiving hoods, slot exhausts, and commercially available pre-manufactured backdraft grossing stations, both recirculating and ducted exhaust types. Out of over 2,000 personal short-term air samples, 307 samples from 163 surveys met the data selection criteria. Over a third of the data were less than the analytical laboratory limits of detection. Using the robust maximum likelihood estimation method for multiple limits of detection, the mean and geometric mean of the dataset for each type of local exhaust system were found to be less than the short-term personal exposure regulatory limit of 2 ppm. Nonparametric Wilcoxon rank-sum pairwise tests of five types of engineering controls showed a statistically significant difference among these controls, with the most effective being the manufactured backdraft grossing stations ducted to the outside, and the least effective being canopy exhaust systems and manufactured filtered recirculating grossing stations. Finally, exposure with each of the major engineering control types was rated by the American Industrial Hygiene Association exposure control rating scheme.

KEYWORDS:

• Censored data analysis
• formaldehyde exposure
• health care
• local exhaust ventilation
• pathology laboratories

Acknowledgments

The authors thank the hard work of all the occupational hygienists who gathered air samples over the last 33 years at Kaiser Permanente facilities, as well as Paul Hewett for guidance with an early draft of this article.

Funding

This study was undertaken by Kaiser Permanente occupational hygiene staff using only data collected in Kaiser Permanente facilities. No outside research grants or funds were applied to this study.