Scalp samples were collected from WBs, EBs, and RBs
of same age group. Scalp hair samples of understudy
workers and referent groups were collected from nape
of the neck. The hair were tied together from 1 cm of
scalp with Teflon thread and cut with stainless steel
scissor, and treated as reported in previous work (Kolachi
et al., 2012; Afridi et al., 2012). Collected samples
were placed in polythene bags, closed with a zipper, and
immediately transported to the laboratory and stored.
Before analysis, each individual scalp hair sample was
cut into approximately 0.5 cm pieces and mixed to make
a representative hair sample. Each hair sample was
washed with dilute Triton X-100, and then rinsed with
distilled water, deionized water, and acetone.