Risk Assessment
Risk Character: Biases that UNDERSTATE risk
"Reductionist View Point" - Synergistic effects (multiple exposures) - Does NOT take into account vulnerable or non-standard population - Tilt toward "natural" ---IGNORING behavior as element of risk - BIAS toward "known" scenarios and available evidence
Steps in Formal Risk Analysis
1) Research * 2) Hazard Identification * 3) Exposure Assessment * 4) Dose- Response Assessment * 5) Risk Characterization 6) Risk Management 7) Risk Communication
Historical Background
1) Risk Analysis 2) Changes in our modern world 3) Risk assessment technology greatly increased 4) Number of government agencies involved in monitoring environmental and human risk has increased 5) INCREASED number of laws and regulations governing the environment and PH 6) INCREASED public interest in environmental and PH risks spurred research in quantifying risks
NRC "Red Book"
1983 -Defined risk assessment -Describes what research do and do not tell us about threats to human health and to environment -Outlines 4 Elements to Risk Assessment
Precautionary Action
Alternative to RA (1992) Rio Declaration --PROTECT environment IF compound or mixture presents a health or environmental hazard, even in the absence of scientific certainty, compound/mixture should NOT be introduced in to environment UNTIL proven safe BURDEN placed on manufactures/ importer instead of long-waiting-decison makers
Hazard ID: Bacterial Mutagenesis Test
Ames Test -Uses genetically engineered strains of Salmonella that are incapable of synthesizing histidine for growth -Variable being tested is its ability to cause reversion of growth on a histidine-free medium
Hazard ID: Biological Testing in Rodents
Bioassays is used to give information about carcinogenicity
NON- Cancer Risk Assessment
Calculate RfD, RfC Use uncertainty factors Threshold Reference Dose = LOAEL
Risk Character: Social Construction of Risk Models
Causal Understandings -Cancer begins with a single mutation Parameters -what matters is level of exposure, chemical structure, DNA repair Measures and Methods characterize parameters - Structural activity studies, animal studies
Risk Character: Biases that OVERTAKE risk
Conservative assumptions in RA -use of SENSITIVE species -consider all route of exposure -high-dose testing Low-dose extrapolation -Ignoring possible mechanisms and thresholds Tilt toward human-made hazards
Hx: Risk Analysis
Developed over the past 40 years out of the need to understand moderns technologically based risks - Silent Spring (book) - Environmental crises - Industrial accidents - Massive man-made disasters
Risk Assessment of Endocrine Disrupters
ED= chemicals that can interfere with endocrine systems at certain doses----->overstimulation 1996- Safe Drinking Water Act & Food Quality Protection Act, MANDATE screening and testing program for endocrine disrupters
Risk Assessment
ESTIMATE the severity of harmful effects to human health and the environment that may result from exposure to agents present in the environment EVALUATE potential adverse health effects, inform a range of decisions to ensure consumer product safety
Hazard ID: Limitations of using Bioassays
Expensive Long time to conduct Too many chemicals to test Validity of Interspecies extrapolations Choice of test animals Routes of exposure Dose-Response issues
Hx: Government agencies involved in monitoring risk
FDA (1906) EPA (1970) State and Local run departments of Environmental protection
Four elements of Risk Assessment
Hazard Identification Exposure Assessment Dose-Response Assessment Risk Characterization
4 Step Risk Assessment Process
Hazard Identification --> Dose-Response & Exposure Assessment -------------------> Risk Characterization
Exposure Assessment
How much of the pollutant are people exposed to during a specific time period? How many people are exposed? Process of MEASURING or ESTIMATING the intensity, frequency, and duration of human exposures to an agent Estimating the exposures that might occur form the release of new chemicals into the environment
Dose-Response Numerical Extrapolation
Humans normally exposed to potential carcinogens at doses many orders LOWER than that used within bioassay studies -----> Uncertainty b/c uses straight line from lowest observed dose
NRC Mission
IMPROVE government decision making/ public policy, INCREASE public understanding, and PROMOTE the acquisition and dissemination of knowledge (science, engineering, technology, health) OVERALL to inform policies and actions that have the power to improve the lives of people in the US and around the world
National Academies
Independent, non-profit institutions that provide advise on pressing challenges Established by Lincoln to have bodies of education to help in developing policies, informing public opinion, and advance the pursuit of science -National Academy of Sciences -National Academy of Engineering -National Academy of Medicine
Dose-Response Biological Extrapolation
Metabolic differences SEPARATE humans and test animals - Lab animals --- HIGHLY inbred - Human population ---genetically heterogenous Current approach: Extrapolation should be based on result s form the more SENSITIVE species
Ecological Risk Assessment
New area of concern Challenges - evaluate risk to populations of thousands of species - complexity and interwoven -->proper selection of end point arises - Degradation of an ecosystem due to not only chemical but biological and physical factors
Cancer Risk Assessment
No threshold Use carcinogen slope factor
Critique of Risk Assessment
PRETENDS to determine "safe" levels of exposure to poisons BUT it CANNOT PROVIDES false assurances while allowing to damage to occur Presents ONLY an approximation of real risk determination
What does Risk Assessment give you?
PROBABILITY that populations/individuals will be harmed and to what degree and the level of confidence associated
What does Risk Management give you?
PROCESS of weighing policy alternatives, selecting appropriate action, integrating results of risk assessment (SOCIAL, ECONOMIC, POLITICAL) to reach a decision
Main Point of Risk Assessment
PROTECT human healthy assuring that compounds we are exposed to will NOT cause harm upon long-term exposure
Ethical Issues in Risk Assessment
Preventative policy NO human experimentation Ethical treatment of animals How conservative should the analyst be?
Red Book: Risk Management
Process of weighing policy alternatives and selecting regulatory action---INTEGRATING results of risk assessment to reach a decision
Hazard ID: Limitations of Analytic Methods
Short-term tests -Problem--reductionism Bioassays -Problem--interspecies extrapolation, choice of animals, route of exposure, dose-response Epidemiology -Problem--confounding factors, many years before conclusions
Hx: Increased # of Laws and regulations governing environment and PH
Superfind Amendements and Reauthorization Act (1986) -Emergency Planning and Community Right- to- know act Food and Drug and Cosmetic Act (1938) Toxic Substance Control Act (1976) - Regulates the introduction of new or already existing chemicals Clean Water Act (1972) -Primary federal law governing water pollution
Ames Test
Test for mutagenicity Simple and indirect assay for potential carcinogens MEASURES frequency of back mutations with a histidine-independent parent strain
Hazard ID: Classification of Carcinogen
US EPA 2005 Guidelines - Carcinogenic to Humans - Likely to be Carcinogenic to Humans - Suggestive Evidence of Carcinogenic Potential - Inadequate Information to Assess Carcinogenic Potential - Not likely to be Carcinogenic to Humans
Red Book: Risk Assessment
Use of the factual base to define health effects of exposure of individuals or populations to hazardous materials
Dose-Response Assessment
What are the different health problems at different exposures? Process of CHARACTERIZING the RELATION between the dose of an agent administered/received and the incidence of an adverse health effect - Takes into account intensity of exposure, patters, and other modifying factors
Hazard Identification
What health problems are caused by the pollutant? Determining if exposure can cause an increase in the incident of an adverse health consequence
Risk Characterization
What is the extra risk of health problems in the exposed population? Step where RISKS are COMPUTED using the information developed in exposure and dose-response assessments INCLUDES an ANALYSIS of UNCERTAINTY in risk
Exposure Assessment: Questions
Who/ What is likely to be exposed? How much exposure may be anticipated? - Mass -Skin surface -Resting respirations -Respiration rate during low activity -Volume of air breathed
Risk Management Strategies
Zero Risk - NO animal carcinogens in food De minimis Risk -prescribes that the decision makers ought to IGNORE improbable risks when making decisions Safety - NO observable effect level (NOEL) Acceptable Risk Risk Tradeoffs