AMERICAN JOURNAL OF INDUSTRIAL MEDICINE 29:569 ( I 996)

LETTER TO THE EDITOR

Exposure Determinants Needed to Improve the Assessment of Exposure

KEY WORDS: exposure assessment, epidemiologic research, exposure determinants, electrical power industry, occupational health

The report by Loomis et al. [ 19941 is a valuable example of the growing efforts to improve the exposure assessment that underlies epidemiologic research and other applications of exposure data. A central theme of the report is a descrip- tion of how the workers were grouped in a manner that would make the exposure data useful to meaningful inferential analysis. One of the occupational groups formed by the authors was “electrical linemen.” This group constitutes a substantial proportion of the total person-years in the epi- demiologic study reported elsewhere [Savitz and Loomis, 19951, as well as a group with relatively high exposures to many of the agents of concern (their Fig. I ; Table 111).

A report in a similar population is of direct relevance to this effort, both because it may help refine the exposure assessment for this group of potentially highly exposed workers, and because it illustrates some of the complexities faced when classifying workers into groups with presum- ably similar exposures [Thind et al., 19911.

Thind and his colleagues found that the electrical line- men group was actually made up of rwo distinct subgroups with substantially different exposure profiles (statistically significant). The reason was differences in seniority (“years of work experience”) between the subgroups. Put simply, the workers with higher seniority within the occupational group did less of the “dirty work,” which in this case was climbing electrical poles. This task was the primary source of dermal exposure to the pentachlorophenol in the treated wood poles. Exposure to magnetic fields may be similarly affected as a result of differences in proximity to the sources.

Address reprint requests to Dr. Manuel R. Gomez, US. Environmental Protec- tion Agency, Office of Research and Development, 401 M Street SW (8603), Washington, DC 20460

Accepted for publication March 28, 1995.

This observation may be relevant to the exposure esti- mates of Loomis et al. if the relationship is present in the populations investigated by them. Indeed, whenever senior- ity plays such a role in otherwise “similar” occupational titles, it could substantially affect estimates of cumulative exposures for long-term employees and the resulting dose- response analysis. Moreover, it is not unreasonable to pos- tulate that the effect may also occur in other industries (e.g., chemical manufacturing).

In the broadest sense, this example illustrates how crit- ical i t is to improve the manner in which we identify and record in exposure databases those factors that act as deter- minants of exposure for different groups of workers [G6- mez, 1993; Beaumont and Dalrymple, 19921.

Manuel R. G6mez, DrPH, MS, CIH U.S. EPA Office of Research and Development Washington, DC 20460

REFERENCES

Beaumont PL. Dalrymple HL (1992): A standard for the presentation of occupational exposure data. Ann Occup Hyg 36:79-98.

Gomez MR (1993): A proposal to develop a National Occupational Expo- Sure Databank. Appl Occup Environ Hyg 8:768-774.

Loomis DP. Peipins LA, Browning SR, Howard RL, Kromhout H. Savitz DA (1994): Organization and classification of work history data in indus- try-wide studies: An application to the electric power industry. Am J Ind Med 26:413-425.

Savitz DA, Loomis DP (1995): Magnetic field exposure in relation to leukemia and brain cancer mortality among electrical utility workers. Am J Epidemiol 141:123-134.

Thind KS, Karmali S, House RA (1991): Occupational exposure of elec- trical utility linemen to pentachlorophenol. Am Ind Hyg Assoc J 52547- 552.

0 1996 Wiley-Liss, Inc.