Table 6.

Selected information available on underlying mechanisms for inter-individual variability due to genetic factors that affect the transport and transformation of organophosphates, VOCs, and metals in humans and animals.

Species class	Metabolism and transport	Notes
Organophosphates	Liver microsomes, CYP-1A2, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, 3A4, and 3A5 (Hodgson, 2003)	Organophosphates share P450s for metabolism (Tang et al., 2001; Rose and Hodgson, 2005). Chlorpyrifos-oxonase (PON1) polymorphism is incorporated into chlorpyrifos PBPK model (Timchalk et al., 2002a)
Metals/metalloids	Glutathione, cystein (Quig, 1998; Patrick, 2003), arsenic methyltransferase (arsenic) (Drobna et al., 2004; Meza et al., 2005; Wood et al., 2006; Thomas et al., 2007), metallothionein (Nordberg and Nordberg, 2000), divalent metal transporter-1 (DMT1) (Garrick et al., 2003; Bressler et al., 2004), bone mineral exchange (lead)	Interactions with essential elements (Goyer, 1997; Ballatori, 2002). Arsenic metabolism affected by CYT19, hNP, and hGSTO1-1 genotypes (Drobna et al., 2004; Meza et al., 2005). Cadmium and lead can alter P450 levels and activities (Moore, 2004; Baker et al., 2005). Metal speciation significantly alters toxicity (Yokel et al., 2006)
VOCs	Glutathione, glutathione-S-transferase, CYP-2E1, 2C6, 2C11, 1A1, and 1A2 (Reddy et al., 2005)	GST genotypes effect metabolism and toxicity (Haber et al., 2002; Qu et al., 2003; Dirksen et al., 2004; Silva Mdo et al., 2004; Reddy et al., 2005)