Heavy metal exposure factors used in eqn (2)–(4).

Factor	Definition	Unit	Value
			Child	Adults
Cs	Soil metal concentration	mg kg−1	—	—
IRs	Soil ingestion rate	mg per day	200	100
SA	Skin surface area available for exposure	cm2 per day	2373	6032
AF	Soil-to-skin adherence factor	mg cm−2	0.2	0.07
IRa	Inhalation rate	m3 h−1	0.53	0.83
ED	Exposure duration	Years	6	20
BW	Body weight	kg	15	80
AT	Averaging time	Days	365 × ED	365 × ED
PEF	Soil-to-air particulate emission factor	m3 kg−1	1.36 × 109
CF	Conversion factor	kg mg−1	1 × 10−6
ET	Exposure time	Hours per day	24
EF	Exposure frequency	Days per year	350
ABS	Absorption factor	Unitless	0.03 for As, 0.01 for other metals