Unit Risk

{
  "id": "MLC-T-ENV-029128",
  "term": "Unit Risk",
  "field": "Environment",
  "definition": "1. The upper-bound excess lifetime cancer risk estimated to result from continuous exposure to an agent at a concentration of 1 µg/L in water, or 1 µg/m³ in air. The interpretation of unit risk would be as follows: if unit risk = 2 × 10⁻⁶ per µg/L, 2 excess cancer cases (upper bound estimate) are expected to develop per 1,000,000 people if exposed daily for a lifetime to 1 µg of the chemical per liter of drinking water.\n\n2. The quantitative estimate in terms of either risk per μg/L drinking water (water unit risk) or risk per μg/m3 air breathed (air unit risk).\n\n3. The upper-bound excess lifetime cancer risk estimated to result from continuous exposure to an agent at a concentration of 1 g/L in water, or 1 g/m3 in air. The interpretation of unit risk would be as follows: if unit risk = 1.5 x 10-6 g/L, 1.5 excess tumors are expected to develop per 1,000,000 people if exposed daily for a lifetime to 1 g of the chemical in 1 liter of drinking water.\n\n4. The unit risk factors (URFs) provide estimates of the risks due to a unit inventory of contaminant (i.e., risk/gram or risk/curie). URFs can be calculated for water, soil, air, and radiation. URFs can be used to calculate risk for quantities greater than unity only if the relationship is linear.",
  "abbreviation": "UR",
  "subject": "Health and safety",
  "references": [
    "Integrated Risk Information System (IRIS) Glossary",
    "Exposure Factors Handbook: Glossary",
    "EPA 2003",
    "RAIS 2004"
  ],
  "url": "https://mlchart.com/terminology/environment/unit-risk/"
}