RISK CONCEPTS

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CHAPTER 2
RISK CONCEPTS
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Chapter 2
This chapter will focus on the basic concept of
environmental risk and risk assessment as applied
to a chemicals manufacturing, processing, and
the impact of exposure to these chemicals on
human health or the environment.
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INTRODUCTION TO
Risk Concepts Risk Assessment Environmental Law
and Regulations Ethics
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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 an
individual organism is put under a certain
constraint (hazard).
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The Risk-Hazard-Exposure-Vulnerability
Relationship
R I S K
VULNERABILITY
EXPOSURE
HAZARD
Sourcehttp//www.ga.gov.au/pdf/GA1421.pdf
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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. 
Sourcehttp//www.agius.com/hew/resource/hazard.ht
m
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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.
Sourcehttp//www.agius.com/hew/resource/hazard.ht
m
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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)

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Indirect Exposure Pathways
Sourcehttp//www.chem.unep.ch/irptc/Publications/
riskasse/A2A4Txtab.PDF
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Types of Risk

• 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
• A consequence of uncontrollable actions performed
  by others. (ex. exposure to environmental
  contaminants)

Natural Disasters
These include floods, hurricanes, earthquakes
and other disasters that are beyond human control.
Sourcehttp//risk.lsd.ornl.gov/minicourse/rap_q1.
shtml
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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
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Risk Assessment Steps
Normaly not included in risk assessment.
Source Environmental Engineering and Science,
Allen and Shonnard, pp.123
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Hazard Assessment
Determining the potential and/or known adverse
effects of a given material

• 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

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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
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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.

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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

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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 the CNS, with
effects such as erethism (increase excitability),
irritability, excessive shyness, and tremors. 
Source www.osha.gov
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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

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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. 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.
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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
NOAEL
1.28 mg/kg-day
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
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Hazard Assessment Canadian References

• WHMIS (Workplace Hazardous Materials
  Information System) http//www.hc-sc.gc.ca/hecs
  -sesc/whmis/index.htm

• CanOSH (Canadas 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

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Hazard Assessment American References

• NIOSH (National Institute for Occupational
  Safety and Health) http//www.cdc.gov/niosh/homepa
  ge.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/

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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

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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
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Dose - Response Curves

• X-axis plots the concentration
• Y-axis plots the response
• dose-response curves typically follow this shape

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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.
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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.
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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.
Sourcehttp//www.epa.gov/ORD/NRMRL/EDC/
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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.
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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.
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Environmental Law and Regulations
Where can we find them?
North American Commission for Environmental
Cooperation http//www.cec.org/home/index.cfm?varl
anenglish
México ? Semarnat http//www.semarnat.gob.mx/wps/p
ortal
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.h
tml
USA ? General Index to Laws http//www.epa.gov/epa
home/rules.html
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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/