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A critical requirement for the success of receptor models for atmospheric particles is that the compositions of particles from all major sources in an area be accurately known.Chemical element balances (CEBs) of 130 samples taken in Washington, D.C. and analyzed for 40 elements yielded nearly the same source strengths when 28 elements are used in the least-squares fit as when only nine carefully chosen elements are used.Certain elements are important to the stability of CEB fits (Na, Ca, V, Mn, As and Pb) and should be measured carefully in particles from sources. For three of the nine elements (Al, Fe and Zn), other elements can serve as surrogates (many lithophiles for Al and Fe, Sb and Cd for Zn).Measurements on many more sources of each important type should be done in order that trends can be observed that will allow one to predict compositions of particles from unmeasured sources.Instack measurements should include collections of at least two size fractions of particles plus vaporphase species. Measurements of at least 20 elements plus some classes of carbonaceous material should be made. Because of the uncertainties in the use of source-emissions inventories to estimate contributions from various sources to ambient levels of suspended particles, many workers have been developing and testing aerosol receptor models (j L ).The basic idea of receptor models is that chemical compositions of particles from various types of sources are sufficiently different that one can determine contributions from the sources by making detailed measurements of the compositions of ambient aerosols and of particles from the sources.Several computational methods have been used ^Current address: Northeast Utilities, Hartford, CT 06101

Objective-This study was undertaken to assess whether contaminated personal clothing worn beneath a coverall (normal workwear) is a source of potentially significant dermal exposure to polycyclic aromatic hydrocarbons (PAHs) in coal liquefaction workers. Methods-An intervention study was conducted over a two week period involving 10 workers that reflected the range of activities performed at the factory. A cross over design was used to examine the influence of normal workwear (personal clothing worn beneath a coverall) and intervention workwear (new coverall, shirt, trousers, underwear, socks, and boots) upon excretion of urinary 1-hydroxypyrene (1-OHP) and skin pad deposition of pyrene. Results-The impact of intervention was noted in three ways: (1) A notable reduction (55%) in the mass of 1-OHP excreted on the first day of the intervention phase was found. The median reduction in mass excreted (22.7 nmol) was significant from zero at the 5% level; (95% confidence interval (95% CI) 9*5-40-8 nmol).(2) A notable reduction (82%) in skin pad deposition of pyrene on the first day of the intervention phase was found. The median reduction of 13.20 ng.cm 2 was significant from zero at the 5% level; (95% CI 7-3-26-4 ng.cm-2). (3) About a 50% reduction in 1-OHP concentration over the working week occurred during the intervention phase; an increase of 2-07 ,umollmol creatinine was found from the start to the end of the work period during the intervention phase compared with an increase of 4-06 umol/mol creatinine during the normal phase. This reduction was not significant at the 5% level. Conclusion-The results indicate that on the first day of the working week investigated, significant reductions in absorbtion (as measured by excretion of urinary 1-OHP) and deposition of PAHs (as measured by skin pad deposition of pyrene) can be effected by improvements in workwear policy. The impact of the improved workwear regimen was also detected by reduction in spot urinary l-OHP concentrations, although this effect was less pronounced. One implication of the findings is that exposure to PAHs may arise from workers' own contaminated personal clothing. As a consequence of this study an improved workwear policy has been implemented at the factory. (Occup Environ Med 1995;52:600-605)