Table 7.
Comparison of Incremental Lifetime Cancer Risk (ILCR) and Target Hazard Quotient (THQ) using previous and revised toxicological reference values by USEPA (2025) under different scenarios
| Rice type | Ingestion rate (IR) (kg/day) |
Concentration (C) of iAs in rice (mg/kg) | Body weight (BW) (kg) | EDI (mg/kg bw-day) |
THQ (using previous RfD 3 × 10–4 mg/kg bw-day) | THQ (using revised RfD 6 × 10–5 mg/kg bw-day) | ILCR [using previous CSF 1.5 (mg/kg bw-day)−1] | ILCR [using revised CSF 32 (mg/kg bw-day)−1] |
|---|---|---|---|---|---|---|---|---|
| Scenario 1: EDI, THQ, and ILCR were calculated based on the IR of Malaysian adults and children | ||||||||
| White ricea | 0.208 | 0.128 | 70 | 3.81 × 10–4 | 1.27 | 6.35 | 5.71 × 10–4 | 1.22 × 10–2 |
| White riceb | 0.208 | 0.128 | 20 | 1.33 × 10–3 | 4.44 | 22.21 | 2.00 × 10–3 | 4.27 × 10–2 |
| Brown ricea | 0.208 | 0.201 | 70 | 5.97 × 10–4 | 1.99 | 9.95 | 8.95 × 10–4 | 1.91 × 10–2 |
| Brown riceb | 0.208 | 0.201 | 20 | 2.09 × 10–3 | 6.96 | 34.82 | 3.31 × 10–3 | 6.69 × 10–2 |
| Scenario 2: EDI, THQ, and ILCR were calculated based on the IR of the UK population for both adults and children (0.015 kg/day) (Menon et al., 2020) | ||||||||
| White ricea | 0.015 | 0.128 | 70 | 2.75 × 10–5 | 0.09 | 0.46 | 4.12 × 10–5 | 8.79 × 10–4 |
| White riceb | 0.015 | 0.128 | 20 | 9.61 × 10–5 | 0.32 | 1.60 | 1.44 × 10–4 | 3.08 × 10–3 |
| Brown ricea | 0.015 | 0.201 | 70 | 4.30 × 10–5 | 0.14 | 0.72 | 6.46 × 10–5 | 1.38 × 10–3 |
| Brown riceb | 0.015 | 0.201 | 20 | 1.51 × 10–4 | 0.50 | 2.51 | 2.26 × 10–4 | 4.82 × 10–3 |
| Scenario 3a) Maximum IR to avoid ILCR (using CSF = 1.5 (mg/kg bw-day)−1 to calculate EDI) | ||||||||
| White ricea | 0.036 | 0.128 | 70 | 6.67 × 10–5 | 0.22 | 1.11 | 1.00 × 10–4 | 1.00 × 10–4 |
| White riceb | 0.010 | 0.128 | 20 | 6.67 × 10–5 | 0.22 | 1.11 | 1.00 × 10–4 | 1.00 × 10–4 |
| Brown ricea | 0.023 | 0.201 | 70 | 6.67 × 10–5 | 0.22 | 1.11 | 1.00 × 10–4 | 1.00 × 10–4 |
| Brown riceb | 0.007 | 0.201 | 20 | 6.67 × 10–5 | 0.22 | 1.11 | 1.00 × 10–4 | 1.00 × 10–4 |
| Scenario 3b) Maximum IR to avoid ILCR (using CSF = 32 (mg/kg bw-day)−1 to calculate EDI) | ||||||||
| White ricea | 0.0017 | 0.128 | 70 | 3.13 × 10–6 | 0.01 | 0.05 | 1.00 × 10–4 | 1.00 × 10–4 |
| White riceb | 0.0005 | 0.128 | 20 | 3.13 × 10–6 | 0.01 | 0.05 | 1.00 × 10–4 | 1.00 × 10–4 |
| Brown ricea | 0.0011 | 0.201 | 70 | 3.13 × 10–6 | 0.01 | 0.05 | 1.00 × 10–4 | 1.00 × 10–4 |
| Brown riceb | 0.0003 | 0.201 | 20 | 3.13 × 10–6 | 0.01 | 0.05 | 1.00 × 10–4 | 1.00 × 10–4 |
| Scenario 4a) Maximum IR based on THQ (using RfD = 3 × 10–4 mg/kg bw-day to calculate EDI) | ||||||||
| White ricea | 0.164 | 0.128 | 70 | 3.00 × 10–4 | 1.00 | 1.00 | 4.50 × 10–4 | 9.60 × 10–3 |
| White riceb | 0.047 | 0.128 | 20 | 3.00 × 10–4 | 1.00 | 1.00 | 4.50 × 10–4 | 9.60 × 10–3 |
| Brown ricea | 0.105 | 0.201 | 70 | 3.00 × 10–4 | 1.00 | 1.00 | 4.50 × 10–4 | 9.60 × 10–3 |
| Brown riceb | 0.030 | 0.201 | 20 | 3.00 × 10–4 | 1.00 | 1.00 | 4.50 × 10–4 | 9.60 × 10–3 |
| Scenario 4b) Maximum IR based on THQ (using RfD = 6 × 10–5 mg/kg bw-day to calculate EDI) | ||||||||
| White ricea | 0.033 | 0.128 | 70 | 6.00 × 10–5 | 1.00 | 1.00 | 9.00 × 10–5 | 1.92 × 10–3 |
| White riceb | 0.009 | 0.128 | 20 | 6.00 × 10–5 | 1.00 | 1.00 | 9.00 × 10–5 | 1.92 × 10–3 |
| Brown ricea | 0.021 | 0.201 | 70 | 6.00 × 10–5 | 1.00 | 1.00 | 9.00 × 10–5 | 1.92 × 10–3 |
| Brown riceb | 0.006 | 0.201 | 20 | 6.00 × 10–5 | 1.00 | 1.00 | 9.00 × 10–5 | 1.92 × 10–3 |
aEstimation based on the average adult’s body weight (USEPA, 2008)
bScenario based on average children’s body weight (Praveena & Omar, 2017)