| Route | C (input) | Key rate | ET (hr/day) | EF (d/yr) | ED (yr) | BW (kg) | ADD (mg/kg-day) | HQ |
|---|---|---|---|---|---|---|---|---|
| Oral | 0.15 mg_L | IR 2 L_day | 0 | 250 | 5 | 70 | 0.0029354207 | 0.9785 |
| Inhalation | 25 ppm_air | IR 20 L_min (MW: 78.11 g/mol) | 8 | 240 | 2 | 70 | 7.1979693879 | 359.8985 |
| Dermal | 1 mg_L | Kp: 0.0012 cm/hr | 2 | 180 | 1 | 70 | 0.0000963757 | 0.0964 |
- Exposure days = EF × ED
- Total absorbed mass = Daily absorbed mass × Exposure days
- Average Daily Dose (ADD) = Total absorbed mass ÷ (BW × AT)
- Hazard Quotient (HQ) = ADD ÷ Benchmark (optional)
Daily absorbed mass (mg/day) = C(mg/L) × IR(L/day)
Daily absorbed mass (mg/day) = C(mg/m³) × IR(m³/hr) × ET(hr/day)
Daily absorbed mass (mg/day) = [C(mg/L)/1000] × Kp(cm/hr) × SA(cm²) × ET(hr/day) × ABS
- Select the exposure pathway that matches your scenario.
- Enter concentration and choose correct units for air or liquids.
- Provide the pathway-specific rate values and exposure time.
- Set frequency, duration, body weight, and averaging time mode.
- Optional: enter a benchmark dose to compute hazard quotient.
- Click Calculate dose, then export CSV or PDF.
Input quality and unit alignment
Good dose estimates start with consistent units and defensible measurements. Use mg/L for liquids and mg/m³ for air; ppm in air requires molecular weight, temperature, and pressure. The calculator converts ppm to mg/m³ using MW×P/(8.314×T), with T in Kelvin and P in kPa. For dilute water samples, ppm is treated as mg/L. Record the sampling duration, detection limit, and whether values are time-weighted averages. If multiple samples exist, use median and 95th percentile to bracket realistic exposure ranges.
Pathway selection and rate parameters
Match the pathway to the dominant contact route. Oral dosing uses daily intake volume (commonly 1–3 L/day for adults). Inhalation uses breathing rate and exposure time; an occupational screening set often starts near 20 L/min for light work and 8 hr/day. Dermal screening uses skin area (hands+forearms can exceed 2000 cm²), permeability Kp (often 1e-4 to 1e-2 cm/hr), and absorbed fraction ABS (0.1–1.0).
Time weighting and averaging choices
Frequency (EF) and duration (ED) drive accumulated mass: exposure days = EF×ED. With EF = 250 d/yr and ED = 5 yr, exposure days equal 1250. Averaging time (AT) controls dilution of the total mass into a daily dose: non-cancer uses ED×365, while cancer uses 70×365. Custom AT supports acute windows, such as 30 days for short-term incidents.
Benchmarking and screening interpretation
Average Daily Dose (ADD) is reported in mg/kg-day. Hazard Quotient (HQ) is ADD divided by a benchmark (for example, an RfD). HQ below 1 suggests exposure is under the screening level, while HQ above 1 flags refinement or risk-management review. Sensitivity is linear: doubling concentration or intake rate doubles daily absorbed mass and ADD, so prioritize accurate C and IR values.
Documentation, exports, and review readiness
Use the notes box to store source tables, assumptions, and scenario identifiers. Export CSV for audit trails and batch comparisons across chemicals or jobs. Export PDF for stakeholders, including pathway, dose, and key inputs. When results are close to decision thresholds, rerun with high/low bounds for C, IR, and ET to create a quick uncertainty band.
What does Average Daily Dose (ADD) represent?
ADD is the time-averaged dose normalized to body weight. The calculator divides total absorbed mass by body weight and averaging time, returning mg/kg-day for comparing different people, durations, and pathways.
When should I use the cancer averaging time option?
Use cancer averaging when assessing lifetime-averaged exposure for carcinogenic risk screening. It sets averaging time to 70 years, which lowers short-duration doses compared with non-cancer averaging and supports consistent cross-study comparisons.
Why does ppm in air require molecular weight?
PPM is a volume ratio, not a mass concentration. Molecular weight, temperature, and pressure are needed to convert ppm to mg/m³ so inhaled mass can be calculated correctly from breathing rate and exposure time.
Is the dermal calculation suitable for detailed assessments?
It is a screening approach for liquid contact using permeability, exposed area, contact time, and an absorbed fraction. For soils, mixtures, or damaged skin, use method-specific dermal uptake models and chemical-specific parameters.
How do I interpret Hazard Quotient (HQ)?
HQ equals dose divided by your benchmark value. HQ below 1 suggests exposure is under the screening level. HQ above 1 indicates a potential concern and usually triggers refinement, better data, or risk-management review.
What should I include in the notes for auditability?
Record sample sources, unit conversions, scenario description, and why each parameter was chosen. Notes appear in exports, helping reviewers reproduce the calculation and understand whether values represent worst-case, typical, or measured conditions.