Commentary: Two Seminal Contributions of S. A. Roach to the Evaluation and Control of Hazardous Substances in Air
Rappaport, S. M. and Flynn, M.
2003 The Annals of oOcupational Hygiene, Vol. 47, No. 5, pp. 343-348,
air contaminants; air turbulence; body burden; control; exposure; ventilation
Rappaport, S. M. and Flynn, M., (2003), "Commentary: Two Seminal Contributions of S. A. Roach to the Evaluation and Control of Hazardous Substances in Air", The Annals of oOcupational Hygiene, Vol. 47, No. 5, pp. 343-348,.
Abstract:
S. A. Roach was a pioneer in the assessment and control of hazardous substances in the working environment during the second half of the 20th century. The two papers discussed in this commentary are generally regarded as his most important scientific contributions. The first paper (Roach, 1977) dealt with the determinants of the body burdens of toxic air contaminants. Using simple kinetic models, he showed how levels of toxicants rise and fall in the body according to the patterns of airborne exposures received during relevant time windows. This led to several useful rules of thumb, including the timing of grab samples for ˇ®fast acting' substances, the appropriate duration of air samples relative to the biological half time, how to deal with unusual work schedules, and how to integrate exposure assessment with control. He also offered sage advice regarding the meaning and interpretation of exposure limits, the importance of repeated monitoring, and the extent to which unacceptable levels of exposure might be reduced. In concluding this work, Roach emphasized that the hygienist can fulfill a central role in occupational health simply by intervening to reduce the body burden. The second paper (Roach, 1981) dealt with the design of effective ventilation systems to control worker exposure to toxic airborne contaminants. By developing a series of simple differential equations, Roach evaluated the impact of turbulent diffusion upon industrial ventilation. He emphasized that the stationary contaminant concentration was proportional to the contaminant generation rate and that velocity alone was not a sufficient design criterion to control exposures. Rather, he argued that the equivalent ventilation rate (the ratio of the contaminant generation rate to the steady concentration in the breathing zone) should be the guiding criterion for ventilation design. Throughout both papers, Roach used fundamental principles to tie together exposure assessment and engineering control, and pointed the way to a science for occupational hygiene. The profession can still learn a great deal from these seminal contributions.
