Table 2 Background-adjusted levels of naphthalene and phenanthrene in the urine of groups of workers exposed to polycyclic aromatic hydrocarbons (PAHs) from three different sources

Source of PAHs	No of subjects	Adjusted naphthalene level (ratio of post-shift level to background level)			Adjusted phenanthrene level (ratio of post-shift level to background level)
Source of PAHs	No of subjects	GM (GSD)	Min	Max	GM (GSD)	Min	Max
Diesel exhaust	39	0.959 (2.00)	0.159	7.61	0.989 (2.74)	0.228	17.5
Asphalt	26	2.20 (2.19)	0.651	10.4	5.04 (3.35)	1.21	219
Coke ovens	28	3.26 (4.38)	0.144	32.8	16.7 (6.06)	0.228	330

These background-adjusted values represent the ratios of levels of naphthalene and phenanthrene in post-shift urine to either pre-shift urine levels (diesel-exhaust and asphalt sources) or factory-control urine levels (coke-oven source).
GM, geometric mean; GSD, geometric standard deviation.