CHAPTER 2 RISK CONCEPTS
Chapter 2 This chapter will focus on the basic concept of environmental risk and risk assessment as applied to a chemical’s manufacturing, processing, and the impact of exposure to these chemicals on human health or the environment.
INTRODUCTION TO : Risk Concepts Risk Assessment Environmental Law and Regulations Ethics
Risk Concepts Risk = f (Hazard, Exposure) Risk : Probability for an individual to suffer an adverse effect from an event. Hazard : Potential for a substance or situation to cause harm or adverse effects to environment and/or humans. Exposure: Magnitude and length of time anindividual organism is put under a certain constraint (hazard).
The Risk-Hazard-Exposure-Vulnerability Relationship R I S K VULNERABILITY EXPOSURE HAZARD Source:http://www.ga.gov.au/pdf/GA1421.pdf
Example I. Hazardous substances and risk Potassium Dichromate is a highly toxic carcinogenic chemical. It is used in some techniques to analyse exhaled breath for alcohol content. However for this purpose it is sealed in a tube, and does not become airborne when air is drawn over it. Therefore, although it is a highly hazardoussubstance, if it is use as described, it does not present any risk to the subject. Source:http://www.agius.com/hew/resource/hazard.htm
Example II. Non hazardous substances and risk Flour would not be considered as a hazardous substance. However, people exposed over a period of time to airborne flour dust and/or dust by skin contact could develop dermatitis, conjunctivitis, rhinitis and even asthma. Thus, long exposure to a low hazard agent may result in a substantial risk and low exposure to a highly hazardous agent may result in a low risk. Source:http://www.agius.com/hew/resource/hazard.htm
Exposure Pathways Include : • Occupational Exposure (occurs in the workplace) • Consumer Exposure (to products) • Environmental Exposure • Direct (exposure to air, soil and water) • Indirect (i.e. contamination through the food chain)
Indirect Environmental Exposure Indirect Exposure Pathways Source:http://www.chem.unep.ch/irptc/Publications/riskasse/A2A4Txtab.PDF
Voluntary Risks A consequence of actions taken out of necessity or by choice. (e.g., driving a car, riding a motorcycle, smoking cigarettes) Involuntary Risks Aconsequenceof uncontrollable actions performed by others. (ex.exposure to environmental contaminants) Types of Risk Natural Disasters These include floods, hurricanes, earthquakes and other disasters that are beyond human control. Source:http://risk.lsd.ornl.gov/minicourse/rap_q1.shtml
Risk Assessment “Risk assessment should estimate adverse impacts to health or the environment and determine whether these impacts pose a serious threat.” National Research Council (USA). Goal: To understand, quantify and communicate risk issues as comprehe nsively as possible. Tools: Laws and regulations concerning the substances
Hazard Assessment (Identification) Dose-Response Assessment Exposure Assessment Risk Characterization *Risk Management Risk Assessment Steps *Normaly not included in risk assessment. Source : Environmental Engineering and Science, Allen and Shonnard, pp.123
Adverse health effects related to chemical exposure: Cancer Endocrine disruptions Reproductive toxicity Hazard estimation : Structure Activity Relationships (SAR) Based on chemical-specific laboratories From reference databases Hazard Assessment “Determining the potential and/or known adverse effects of a given material”
Toxicological Hazards Substances that pose toxicological hazards can be divided into four categories: Hazard Classification of Substances Carcinogenic; Mutagenic; Toxic to Reproduction. Respiratory Sensitisers. SPECIAL Very toxic; Toxic; Skin Sensitisers; Corrosive. HIGH MEDIUM Harmful Substances examined but not meeting the criteria of the other hazard categories. LOW
Carcinogenic Assessments Genotoxic vs. Non-Genotoxic Carcinogens • A Genotoxic Carcinogen “always” causes cancer regardless of its quantity or concentration – one molecule could alter DNA and cause a mutation. • A Non-Genotoxic Carcinogen has a “safe” threshold quantity. • If the nature (genotoxicity) of the substance is unknown, the carcinogen is assumed to be genotoxic.
Carcinogenic SubstancesClassification • Group A : Carcinogenic to Humans • Group B1 : Probably Carcinogenic to Humans based on limited human evidence of carcinogenocity • Group B2 : Probably Carcinogenic to Humans based on sufficient animal evidence, but inadequate human evidence • Group C : Possibly Carcinogenic to Humans • Group D : Not classifiable for Human Carcinogenicity • Group E : Evidence of Non-Carcinogenicity for Humans
Example of a Carcinogenic Chemical Mercury (Hg) is an example of an air toxic Acute (short-term) exposure to high levels of mercury in humans results in central nervous system (CNS) damages which can result in, among others, tremors and mood changes. Chronic (long-term) exposure to high levels of mercury in humans also affects theCNS, with effects such as erethism (increase excitability), irritability, excessive shyness, and tremors. Source: www.osha.gov
Non-Carcinogenic (Toxic) Effects Assumed to have a dose or exposure threshold Measurements : • Rf D (Reference Dose) [=] mg pollutant/kg body weight/day • Rf C (Reference Concentration) [=] mg/m3 • Derived from NOAEL (Non Observed Adverse Effect Level) and LOAEL (Lowest Observed Adverse Effect Level) using some uncertainty factors
Non-Carcinogenic EffectsHow to Calculate... Rf D = NOAEL FA FH FS FL FD Where: FA is an adjustment factor to extrapolate from animal to human populations. FH is an adjustment factor for differences in human susceptability. FS is an adjustment factor used when data are obtained from subchronic studies. FLis an adjustment factor applied when the LOAEL is used instead of the NOAEL. FDis an adjustment factor applied when the data set is dubious or incomplete.
Example : Reference Dose Calculation For 4-Clorophenol, 2.58 mg/kg-day is considered a LOAEL, and 1.28 mg/kg-day is considered a NOAEL. In rats, liver effects were assessed by the determination of liver weights. 1. Using the NOAEL 1.28 mg/kg-day NOAEL Rf D = = = 0.00128 mg/kg-day FA FH FS 10 x 10 x 10 2. Using the LOAEL 2.58 mg/kg-day LOAEL Rf D = = = 0.000258 mg/kg-day FA FH FS FL 10 x 10 x 10 x 10 Source: http://www.atsdr.cdc.gov/toxprofiles/tp107-a.pdf
Hazard Assessment: Canadian References • WHMIS (Workplace Hazardous Materials Information System)http://www.hc-sc.gc.ca/hecs-sesc/whmis/index.htm • CanOSH (Canada’s National Occupational Health and Safety) http://www.canoshweb.org/en • CCOHS (Canadian Centre for Occupational Health and Safety ) http://www.ccohs.ca • MSDS (Material Safety Data Sheets) • http://www.hc-sc.gc.ca/pphb-dgspsp/msds-ftss
Hazard Assessment: American References • NIOSH (National Institute for Occupational Safety and Health) http://www.cdc.gov/niosh/homepage.html • ATSDR (American for Toxic Substances and Diesease Registery) http://www.atsdr.cdc.gov • IRIS (Integrated Risk Information System) http://www.epa.gov/ngispgm3/iris/index.html • National Library of Medicine • Hazardous Substances Data Bank • http://chem.sis.nlm.nih.gov/hsdb/ • Toxnet • http://sis.nlm.nih.gov/sis1/
Hazard Assessment: Mexican References • Information about Health and Safety Laws • http://www.salud.gob.mx/unidades/dgaj/ • http://www.salud.gob.mx • Information about environmental laws and regulations • http://www.semarnat.gob.mx/wps/portal
Dose-Response Assessments Characterizing the relationship between the quantities (dose) and resulting adverse effects (response) of a given material. Requires dose-response curves that demonstrate the effects of chronic toxicity
Dose - Response Curves • X-axis plots the concentration • Y-axis plots the response • dose-response curves typically follow this shape
Exposure Assessments “Determining not only the size and nature of the population affected by a potential exposure but also the length of time during which they may be exposed.” Normally the exposure assessed will be an external exposure. Where the conclusion is that this level is "of concern", it may be necessary to determine the internal exposure.
Risk Characterization “Estimating the magnitude of the adverse effects on given populations by compiling all the data from the three previous steps.” This stage involves the quantitation of the risk following consideration of the exposure and the dose-response (effect) relationships.
The function of the system is to regulate a wide range of biological processes, including: . • Control of Blood Sugar. • Growth and Function of Reproductive Systems. • Regulation of Metabolism. • Brain and Nervous System Development. Disruptions in hormonal balance at critical life stages may have long-lasting effects. Source:http://www.epa.gov/ORD/NRMRL/EDC/
Risk Management “Identifying, evaluating, selecting and implementing actions to reduce risk to populations and environments.” This step is a scientific attempt to identify and estimate the true risks, by considering the : • Hazard(s) • Dose-Response Relationship • Risk Characterization. Potential solutions are then proposed, selected and implemented in order to minimize the risks.
Environmental Law and Regulations Why are these laws made? • - To protect human health as well as the environment by placing limits on the concentration and quantity of different chemicals in manufacturing waste streams. - Recently, laws and regulations encouraging pollution prevention have been put in place to encourage waste minimization instead of controlling the regulated substances.
Environmental Law and Regulations Where can we find them? • North American Commission for Environmental Cooperation • http://www.cec.org/home/index.cfm?varlan=english • México Semarnat • http://www.semarnat.gob.mx/wps/portal • Canada Canadian Environmental Protection Act • http://laws.justice.gc.ca/en/C-15.31/ • General Index to Laws • http://laws.justice.gc.ca/en/index.html • USA General Index to Laws • http://www.epa.gov/epahome/rules.html
Engineering Ethics “In addition to the laws and regulations by which chemical engineers should abide, there exist codes of ethics.” These codes of ethics can be found : • American Institute of Chemical Engineers (AIChE) • http://www.aiche.org/about/ethicscode.htm Canadian Society for Chemical Engineers (CSChE) http://www.chemeng.ca/ethics • Instituto Mexicano de Ingenieros Quimico (IMIQ) • http://www.imiq.org/ The Online Ethics Center for Engineereing and Science http://www.onlineethics.org/