Table 5: Risk assessment outcome manifestations due to inconsistent toxicity factor rounding.

 

 

Soil chemical

Hypothetical exposure point concentration (mg/kg)

Incidental soil ingestion hazards (HQs)

for a hypothetical site resident1

Mathematical RfDo

 

HQ

 

‘Rounded Up’ RSL Table RfDo

 

HQ

 

endrin

 

 

25

 

2.50E-04

 

1.20

 

3.00E-04

 

1.00

 

hexabromodiphenyl ether

 

17

 

1.50E-04

 

1.36

 

2.00E-04

 

0.93

 

octabromodiphenyl ether

 

250

 

2.51E-03

 

1.20

 

3.00E-03

 

1.00

 

 

 

Soil chemical

Hypothetical exposure point concentration (mg/kg)

Mathematical

RfDo

 

HQ

 

‘Rounded Down’ RSL Table RfDo

 

HQ

 

chloroform

 

1000

 

1.29E-02

 

0.93

 

1.00E-02

 

1.21

 

 

furan

 

100

 

1.40E-03

 

0.86

 

 

1.00E-03

 

1.20

 

trichlorobenzene, 1,2,4-

 

1000

 

1.48E-02

 

0.81

 

1.00E-02

 

1.20

1Computed HQs do not follow straightly from the toxicity information of the 2019 RSL Table. That RSL Table bears numerous erroneous risk-based concentrations (rbc), as in those for the incidental soil ingestion uptake route of residents and industrial workers. The erroneous values reflect standard exposure factors (e.g., adult body weight; exposure duration [in years]) adopted several years ago (USEPA 2014), not having been implemented in the rbc calculations.