Environmental Regulations and Risk Assessment
Domain scope
This domain tests the risk assessment paradigm, exposure calculations, risk-based screening, and the regulatory frameworks that drive investigation and cleanup.
Core rules and concepts
- Risk assessment has four steps: hazard identification, dose–response assessment, exposure assessment, and risk characterization.
- Cancer risk = CDI × SF; noncancer hazard quotient HQ = CDI/RfD; the hazard index sums HQs across pathways.
- Convert exposure inputs carefully: 100 mg/day = 0.0001 kg/day.
- For cancer, average lifetime exposure over 70 years; for noncancer, average over the exposure duration.
- CERCLA and RCRA drive federal cleanup, while MCLs and state soil screening levels provide benchmarks.
Worked example
CDI = (C × IR × EF × ED)/(BW × AT). Use C = 10 mg/kg, IR = 0.0001 kg/day, EF = 350 d/yr, ED = 6 yr, BW = 15 kg, AT = 2,190 d. CDI = (10 × 0.0001 × 350 × 6)/(15 × 2,190) = 6.4 × 10−5 mg/kg-day. With RfD = 0.0003, HQ = 0.21.
Traps that cost marks
Failing to convert mg/day to kg/day; using the wrong averaging time; summing cancer risk and hazard quotients interchangeably; and ignoring child versus adult exposure assumptions.