RISK CONCEPTS

CHAPTER 2

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.

Risk Concepts

Risk Assessment

Environmental Law and Regulations

Ethics

INTRODUCTION TO :

Risk Concepts

Risk = f (Hazard, Exposure)

Exposure : Magnitude and length of time an individual organism is put under a certain constraint (hazard).

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 VULNERABILITYR I S K

HAZARD

Source:http://www.ga.gov.au/pdf/GA1421.pdf

The Risk-Hazard-Exposure-Vulnerability Relationship

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 hazardous substance, if it is use as described, it does not present any risk to the subject. 

Source:http://www.agius.com/hew/resource/hazard.htm

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

II. Non hazardous substances and risk

Example

• Occupational Exposure (occurs in the workplace)

• Consumer Exposure (to products)

• Environmental ExposureDirect (exposure to air, soil and water)Indirect (i.e. contamination through the food chain)

Exposure Pathways Include :

Source:http://www.chem.unep.ch/irptc/Publications/riskasse/A2A4Txtab.PDF

Indirect Environmental Exposure

Indirect Exposure Pathways

Types of RiskVoluntary Risks A consequence of actions taken out of necessity or by choice. (e.g., driving a car, riding a motorcycle, smoking cigarettes)

Involuntary RisksA consequence of uncontrollable actions performed by others. (ex. exposure to environmental contaminants)

Source:http://risk.lsd.ornl.gov/minicourse/rap_q1.shtml

Natural

Disasters These include floods, hurricanes, earthquakes and other disasters that are beyond human control.

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

Risk Assessment Steps

Source : Environmental Engineering and Science, Allen and Shonnard, pp.123

Hazard Assessment

(Identification)

Dose-Response Assessment

Exposure Assessment

Risk Characterization

*Risk Management *Normaly not included in

risk assessment.

Hazard Assessment

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

“Determining the potential and/or known adverse effects of a given material”

Toxicological HazardsSubstances that pose toxicological hazards can be divided into four categories:

SPECIAL

HIGH

MEDIUM

LOW

Hazard Classification of Substances

Carcinogenic; Mutagenic; Toxic to Reproduction.Respiratory Sensitisers.

Very toxic; Toxic; Skin Sensitisers; Corrosive.

Harmful

Substances examined but not meeting the criteria of the other hazard categories.

Carcinogenic AssessmentsGenotoxic 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 Substances Classification

• 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

Mercury (Hg) is an example of an air toxic

Chronic (long-term) exposure to high levels of mercury in humans also affects the CNS, with effects such as erethism (increase excitability), irritability, excessive shyness, and tremors. 

Example of a Carcinogenic Chemical

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.

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 FDWhere:

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.

FL is an adjustment factor applied when the LOAEL is used instead of the NOAEL.

FD is an adjustment factor applied when the data set is dubious or incomplete.

Example : Reference Dose CalculationFor 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

Rf D = NOAEL

FA FH FS

Rf D = LOAEL

FA FH FS FL

2. Using the LOAEL

= 1.28 mg/kg-day

10 x 10 x 10= 0.00128 mg/kg-day

= = 2.58 mg/kg-day

10 x 10 x 10 x 100.000258 mg/kg-day

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:

Disruptions in hormonal balance at critical life stages may have long-lasting effects.

Source:http://www.epa.gov/ORD/NRMRL/EDC/

• Control of Blood Sugar.• Growth and Function of Reproductive Systems.• Regulation of Metabolism.• Brain and Nervous System Development.

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 RegulationsWhere can we find them?

North American Commission for Environmental Cooperationhttp://www.cec.org/home/index.cfm?varlan=english

México Semarnathttp://www.semarnat.gob.mx/wps/portal

Canada Canadian Environmental Protection Act http://laws.justice.gc.ca/en/C-15.31/

General Index to Lawshttp://laws.justice.gc.ca/en/index.html

USA General Index to Lawshttp://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 Sciencehttp://www.onlineethics.org/