Table 1.

The distribution of age and gender for subjects from these three plants.

	Plant A	Plant B	Plant C
Male	132	46	81
Female	0	0	82
Smoking number	68	28	no data
Average age ± 1 s.d.	38.9 ± 7.7	35.8 ± 6.7	31.7 ± 8.7