Lecture 4: Risk Analysis BIO410- Ecology and Environmental Engineering FALL 2016 By Jasmin Šutković 31h Oct. 2016 Lecture 4: Risk Analysis

Outline WHAT IS RISK ANALYSIS ASSESSMENT OF RISK PROBABILITY DOSE-RESPONSE EVALUATION POPULATION RESPONSES EXPOSURE AND LATENCY EXPRESSION OF RISK RISK PERCEPTION ECOSYSTEM RISK ASSESSMENT

What is meant by Risk Analysis? Environmental engineer is asked to understand and reduce the risks from hazards from environmental pollution to the environment and to public health in both long and short term. Risk analysis is introduced here as a tool of the environmental engineer that crosses the boundaries of science, engineering, and risk analysis.

Risks… How to determine the comparative risks from various environmental pollutants and, further, which risk(s) is it most important to decrease or eliminate. Adverse effects on human health are often difficult to identify and to determine.

In general, a risk factor should meet the following conditions: Exposure to the risk factor precedes in the appearance of the adverse effects. The risk factor and the adverse effect are consistently associated. That is, the adverse effect is not usually observed in the absence of the risk factor. The more of the risk factor there is, or the greater its intensity, the greater the adverse effect. The occurrence or magnitude of the adverse effect is statistically significantly greater in the presence of the risk factor than in its absence.

Example of risk factor with adverse side affects SMOKING Why ? For example, SMOKING is unhealthy, both to the smoker (primary smoke risk) and to those around the smoker (secondary smoke risk). Specifically, lung cancer, chronic obstructive pulmonary disease, and heart disease occur much more frequently among smokers The increased frequency of diseases is statistically significant!! Cigarette smoke is thus a risk factor for these diseases; smokers and people exposed to secondhand smoke are at increased risk for them.

ASSESSMENT OF RISK Risk assessment is a system of analysis that includes four tasks: identification of a substance (a toxicant) that may have adverse health effects, scenarios for exposure to the toxicant, characterization of health effects, and an estimate of the probability (risk) of occurrence of these health effects.

Toxicant or not?? The decision that the concentration of a certain toxicant in air, water, or food is acceptable or unacceptable is usually based on a risk assessment!!! In most cases, the first intimation that a substance is toxic is its association with an unusual number of deaths! Mortality risk=risk of death!

PROBABILITY Probability is the measure of the likelihood that an event will occur.  Often confused with frequency ! In statistics, frequency is defined as "the number of items occurring in a given category " Because frequencies are used to estimate probabilities in risk assessment. One such use is the estimate of the risk of being in an automobile accident.

Example: car accidence in USA Note that probability is a dimensionless number and is always less than unity. A probability of 1 means that the event has a 100% chance of occurring, or is a certainty (0.1 probability =10% chance) A frequency, on the other hand, has dimensions and can have a value larger than unity, depending on how the frequency is defined. Consider the following example

In USA there is an observed track accident rate (frequency) of 3 In USA there is an observed track accident rate (frequency) of 3.5x10 -7 per truck kilometer = observed frequency. From here we can estimate the average probability of car accidents. If there are 20,000 truck shipments of hazardous materials per year for 10 years, and the average distance traveled is 1000 km per shipment, there would be

DOSE-RESPONSE EVALUATION The response of an organism to a pollutant always depends in some way on the amount or dose of pollutant to the organism. The doses impact depends of exposure pathway. The same substance may have a different effect depending on whether it is inhaled, ingested, or absorbed through the skin, or whether the exposure is external. In general, the human body detoxifies an ingested pollutant more efficiently than an inhaled pollutant.

Some characteristic features of the dose response relationship are as follows: Threshold Total Body Burden Physiological Half-Life Bioaccumulation and Bio-concentration Exposure Time and Time vs Dosage Synergism LC50 and LD50. Homesis Hormesis is a term used by toxicologists to refer to a biphasic dose response to an environmental agent characterized by a low dose stimulation or beneficial effect and a high dose inhibitory or toxic effect. https://www.google.ba/search?q=latency&oq=latency&aqs=chrome..69i57j0l5.2710j0j7&sourceid=chrome&ie=UTF-8

POPULATION RESPONSES Individual responses to a particular pollutant may differ widely; dose-response relationships differ from one individual to another. Threshold is different Individual responses and thresholds also depend on age, sex, and general state of physical and emotional health Regulatory agencies try to set such levels below threshold level for 95% or more of the U.S. population.

EXPOSURE AND LATENCY Pollutions may cause problems many years after the official event of pollution Many cancers grow very slowly and are noticed (expressed) many years, or even decades, after exposure to the potentially responsible carcinogen. The length of time between exposure to a risk factor and expression of the adverse effect is called the latency period! Latency is a time interval between the stimulation and response, or, from a more general point of view, a time delay between the cause and the effect of some physical change in the system being observed

EXPRESSION OF RISK EPA ( US environmental agency )developed quantitative expressions for risk. Risk is defined as the product of probability and consequence, and is expressed as the probability or frequency of occurrence of an undesirable event For example, if 10% of the students in a course were randomly given an “F,” the “risk” of getting “F’ is 0.1 “F’ per total number of grades assigned.

The frequency of Occurrence of adverse health effects in a population is written as:

Frequency = probability This frequency is often called a probability P, and written without units. Because of this common (though confusing) usage, we will refer to “probability” throughout the remainder of this chapter.

RISK PERCEPTION Different people perceive differently the hazardous effects of the pollutions they create! In order to perceive we need to have knowledge about the risk, whether the risk is undertaken voluntarily and what are the benefits of vaoding the risk ? While engineers deal with mitigation of estimated risks, they must often take risk perception into account.

ECOSYSTEM RISK ASSESSMENT Ecosystem risk assessment is done in the same general way as human health risk assessment, but the identification of the species at risk is a far more complex process than in human health risk assessment.