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RISK DUE TO INDOOR AIR POLLUTANTS. (IAQ). What is Risk Assessment?. Risk assessment: provides information on the health risk Characterizes the potential adverse health effects of human exposures to environmental hazards
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What is Risk Assessment? • Risk assessment: provides information on the health risk • Characterizes the potential adverse health effects of human exposures to environmental hazards • Extent to which a group of people has been or may be exposed to a certain chemical is determined • Extent of exposure is then considered in relation to the kind and degree of hazard posed by the chemical, thereby permitting an estimate to be made of the present or potential health risk to the group of people involved • Risk management: is the action taken based on the risk assessment
Purpose of Risk Assessment • Characterizes the types of health effects expected • Estimates the probability (risk) of occurrence of these health effects • Estimates the number of cases with these health effects • Provides an acceptable concentration of a toxicant in air, water, or food • Covers cancerous as well as non cancerous chemicals
Process of Risk Assessment • Hazard identification : A determination is made as to whether human exposure to the agent in question has the potential to increase the incidence of cancer • Dose-response assessment: A quantitative relationship is derived between the dose, or more generally the human exposure, and the probability of induction of a carcinogenic effect • Exposure assessment: An evaluation is made of the human exposure to the agent. Exposure assessments identify the exposed population, describe its composition and size, and present the type, magnitude, frequency, and duration of exposure • Risk characterization: The exposure and dose-response assessments are combined to produce a quantitative risk estimate and in which the strengths and weaknesses, major assumptions, judgments, and estimates of uncertainties are discussed
Technical hazard Characterization • Population Characterization of Risk Assessment • Hazard Assessment • Technical Dose response Characterization • Risk characterization summary • Data Response Assessment • Integrative analysis • Technical Exposure Characterization • Exposure Assessment
What is Risk? • Hazard is the potential of an entity (or activity) to cause harm to nature, property, or people. • Risk from a hazard: risk (harm/unit time) = frequency (event exposure/ unit time) * Consequence (harm/event exposure])
What is Total Risk? • Total risk: R = i =1N∑ R i= 1,2,3,…,n where, i is hazard • For low value of C , R = f x Ch • For high value of C, R = f x Chn where n is some known number that reflects the roles of disruptions by severe accidents, as well as the public perception
How to calculate frequency (f)? • Frequency (f) = Exposure / Unit time = Daily amount of air pollutant inhaled over a life time / person’s weight = (Breathing rate ( m3 / day) x indoor concentration ( µg/ m3) ) / ( Weight of an individual in kg) = (B x C) / W where, B is breathing rate, C is indoor concentration, W is weight of an individual. • Units of frequency is ( µg / kg-day)
How to calculate Consequence (C) ? • Consequence (c) = Life time excess cancer risk / Daily exposure to 1 µg of the pollutant/weight of an individual = βa x Kah x I where, βa = “potency” of the pollutant for inhalation in (µg/kg-day)-1 Kah = a conversion factor expressing the ratio of the risk to a human to the corresponding risk to an animal based on inhalation toxicity I = a factor relating inhalation data to risk if other pathways were also available, also known as data potency
What is lifetime excess cancer risk ? • It is expressed as follows: R = (B x d). (βa x K ah x I ) W
Example of lifetime excess cancer risk • Risk to an adult from the exposure to tetrachloroethylene is calculated as follows by using the given information B = 20 , W = 70 , d = 3.5 , βa = 9.2 x 10-6 , Kah = 1 , I = 1 By using the above formula and substituting the above given values in the formula we get the lifetime excess cancer risk to an individual is R = 9.2 x 10 -6. • The above value of risk implies that an individual has a 9.2 chance in a million of getting cancer over his or her lifetime because of the daily exposure to tetracholoroethylene at a concentration level of 3.5 µg/m3 of air. If an individual has a life span of 70 years, then chance of getting cancer in any one year is 9.2/70 = 0.13 in a million
Why are risk studies conducted on Animals? • While carrying out experiments there are risks from a spectral of real, suspected or conjured hazards related to chemical and biological substances. • The effect from a single substance on humans under controlled conditions cannot be studied. • Therefore, studies are conducted on test animals that are subjected to massive doses of a substance on a relatively short time scale. • These test conditions carried out on animals like rats and monkeys are atypical of human exposures. • The results of these animal studies are extrapolated for applications to human conditions by the use of mathematical models. • The mathematical models are actually equations which are formulated and solved for applications to animal test conditions
Understanding Risk Factors • EPA Reference Dose: Maximum daily acceptable oral dose of a toxic substance, smaller numbers mean a pollutant is more toxic • Carcinogenic Potency factor or Carcinogenic Slope Factor: a way to measure the safe dose of a toxin. The EPA says that this chemical is safe to this dose with a 95th percentile of certainty. Higher numbers are safer.
