Health Risk Assessment PDF

Health Risk Assessment  Objectives At the end of this session, students should be able to: – Define risk, risk assessment, hazard – List the four steps of health risk assessment – Describe the dose-response relationship – Calculate the dose or exposure – Formulate the...

Health Risk Assessment  Objectives At the end of this session, students should be able to: – Define risk, risk assessment, hazard – List the four steps of health risk assessment – Describe the dose-response relationship – Calculate the dose or exposure – Formulate the statement of risk characterization  What is Risk Risk is the probability of occurrence of adverse health effect resulting from human exposure to environmental hazard  Risk Assessment Risk assessment is a process intended to estimate the health risk to a given population resulting from exposure to specific toxicant.  Risk Assessment Answer this Question If people exposed to specific concentration of toxic chemical over specific period of time, – Will it harm them?  Steps of Health Risk Assessment Hazard identification Hazard guideline value identification Exposure assessment Risk characterization  Hazard Identification Hazard identification is generally the first step in a risk assessment This step involves: – Establishing the identity of the chemical of interest (sampling and analysis) – Determining whether this chemical is hazardous http://www.inchem.org Hazard Guideline Value Identification This step involves quantitative information on the toxicant which can be obtained from dose- response assessment This includes identification of:- – ADI = Rfd = Safe human dose (Non-carcinogenic health risk) – Slope factor (SF) (Carcinogenic heath risk)  Exposure assessment Exposure assessment is used to determine whether people are in contact with a hazardous chemical and, if so, – to how much (concentration) – by what route (route of exposure) – through what media (air, water, food and soil) – for how long (days)  Rate of exposure Rate of exposure for a chemical is typically referred to as average daily dose, with units of milligrams of chemical per kilogram of body weight per day (mg/kg body weight /day).  Rate of Exposure Con,, Example Consider adult ingestion of soil contaminated with a toxicant and concentration of this toxicant in soil is 100 milligrams per kilogram (mg/kg). The daily soil ingestion rate of adult was 100 milligrams per day (mg/day). Assume the person is on site 5 days per week, 52 weeks per year, for 30 years. Calculate the exposure rate or dose. Solution Exposure rate = (Concentration * Contact rate * Exposure duration)/ (Body weight * Average time) Exposure rate = [(100 mg/kg) * (100 mg/day) * (5*52*30 day)]/ [ (30*365 day) * (70 kg)* 1000000] = 0.0001 mg/kg/day  Rate of Exposure Con,, Example consider human exposure to a water supply contaminated with 35 milligrams per liter (mg/L) methylene chloride. Calculate an adult exposure dose assuming that the body weight of 70 kilograms (kg) and the water intake rate of 2 liters per day (L/day) Solution  Risk Characterization Risk characterization is the last step of risk assessment It is typically a quantitative statement This statement is derived by: – comparing the estimated exposure with a guideline value (non-carcinogenic risk) – calculating the excess lifetime cancer risk associated with the estimated exposure  Risk Characterization Non-carcinogenic health risk Estimation – Non-carcinogenic health risk can be estimated using hazard quotient (HQ) 𝑅𝑎𝑡𝑒 𝑜𝑓 𝐸𝑥𝑝𝑜𝑠𝑢𝑟𝑒 𝐻𝑄 = 𝑅𝑓𝐷 HQ value < 1 indicates no significant or acceptable risk HQ values > 1 indicates the potential for adverse health effects  Risk Characterization Carcinogenic health risk Estimation – Carcinogenic health risk can be estimated using incremental lifetime cancer risk (ILCR) 𝐼𝐿𝐶𝑅 = 𝑅𝑎𝑡𝑒 𝑜𝑓 𝐸𝑥𝑜𝑠𝑢𝑟𝑒 × 𝑆𝐹 – Where SF is slope factor The ILCR of < 1 x 10-6 is considered acceptable  Health Risk Estimation Consider human exposure to a water supply contaminated with 0.19 (mg/L) arsenic (As). Provide an estimation for the carcinogenic and non-carcinogenic health risks associated with drinking of this water over the lifetime for both adults. If you know that the water drinking rate of an adult is 2 liter/day, the average weight of adults is 70 kg, the RfD of arsenic is 3 X 10-4 mg/kg-day and the slope factor (SF) is 1.5 per mg/kg-day.  REFERENCES WHO human health risk assessment toolkit: chemical hazards, WHO Press, World Health Organization, Geneva, Switzerland, 2010. Phillip L. Williams, Robert C. James and Stephen M. Roberts, 2000. Principles Of Toxicology: Environmental and Industrial Applications, Second edition, John Wiley & sons, inc. Ernest Hodgson, Modern Toxicology, John Wiley & Sons, Inc USEPA, 1993, introduction to air pollution