ESPM C167 Unit III. Risk Assessment

Cassaret and Doul's Model: The four basic components of risk assessment

Systematic characterization of potential health damages resulting from human exposures to hazardous agents or situations

1. hazard identification

2. exposure assessment

3. dose-response

4. risk characterization/ communication

A) hazard identification

The different types of scientific evidence used in toxicological and epidemiological studies

- toxicological

- epidemiological

structure in / pros and cons of epidemiological/toxicological

- structure activity (modeling), vitro (cell and tissue)

epidemiological is hard bc expensive, often unethical but can be opportunistic. most definitive test

toxicological = lab based --> draw more assumptions

case-control studies

Identify cases with disease then examine who had exposure of interest (Diseased group and non diseased group)

pros/cons of case-control studies

Good for rare diseases - cancer or diseases with long latency periods

More susceptible to selection and observation bias as well as exposure recall bias

cohort designs

Identify an "exposed" population group b4 disease occurs

( "presence" and "absence" group)

cohort design pros/cons

Good for common diseases in large numbers & over short follow up periods.

Less susceptible to bias

expensive and hard to track over time

Examples of signature diseases

Disease that is a clear indication of a link to a specific cause (chemical agent)

- Thalidomide

- Asbestos

- Minamata disease

Thalidomide - diethylstilbestrol (DES)

for miscarriages in germany = baby deformities in vaginal/penis and menstrual irregularities/ovarian cancer and reproductive tract dysfunction in grandchildren

Asbestos

A mineral once used in home insulation and other materials that can cause respiratory diseases/lung cancers

Minamata disease (how and what)

Methyl mercury dumped in minamata bay

- people ate fish

- preg women = kids with severe congenital cerebal palsy

Demonstrate definitive link

Exposures need to be high and/or clearly isolatable to show a relationship

Most ppl are exposed to low levels = hard to determine exposure

B) Exposure assessment (& pathways)

Movement of chemicals through various media

differences in exposure pathways between test animals and humans - e.g. for humans exposed through food, air,etc.

C) Dose-response

Determines relationship between dose and severity of toxic effect

evaluate relationship between dose and toxic severity → predicts disease/outcome responses

Dose-response curve

2 curves: threshold versus linear

Threshold have low level dose that is said to be safe but unsafe past threshold point (non carcinogens)

Linear has no safe level of toxicant (carcinogens)

dose response drawbacks

Extrapolation from

default assumption in extrapolation of results from animals to humans

high dose in animals compared to long term low level dose in humans --> over/underestimate cancer risk

dose response assumptions

-over/underestimate cancer risk

- humans respond like most sensitive test species

how do humans match toxicological studies

compare them to the most sensitive test subject

D) Risk characterization/communication

integrative analysis

risks of pollutant, magnitude of uncertainty, hazard potentials

Risk characterization drawbacks

assumptions from study to study

ethical issue: risk or uncertainty?

need proof for policy claims

The objectives of risk assessment

1. Protect human and ecological health

2. Balance risks and benefits and target levels

4. Set priorities for program activities

5. Estimate residual risks and extent of risk reduction after steps are taken to reduce risks

Arguments in favor and against traditional approaches to risk assessment

traditional = cassaret and doul

can use it to apply make standardized priorities for what we need to research and fund, setting levels of safe exposure in policy

unfavor = uncertainty

Susceptibility differences: childhood, infant, and in utero exposures

genetics, other exposure, preexisting conditions (e.g. birthweight asthma , EJ, many exposures)

children development:

(1) immaturity of biochemical and physical func = developing organs more vulnerable to injury (e.g. gain weight rapidly, central nervous system, sex organs, myelination — all developing during adolescence)

(2) behavioral (e.g. food intake, explore world using hands and mouths)

illustrating key environmental health concerns associated with children

(mercury, lead, endocrine disrupting compounds, or other hazards)

use and advantages and limitations of toxicological studies

use: look for alters in: brain development/ reproductive tract/puberty

limits: high dose needed/ extrapolation to humans (most sensitive of study)

advantages: controlled experimental conditions, closes systems, control docjs

Yassi, et al. (2001) "Epidemiological Methods"

- Epidemiological methods utilize various study types to identify hazards and dose-response relationships.

- Descriptive studies offer an overview of health issues, while analytical studies delve into causal factors and intervention effectiveness.

- Guidelines such as temporal relation, plausibility, mechanism of action, and consistency aid in assessing causal relationships and understanding causation.

Faustman, M. and G. Omenn (2010)

"Casarett and Doul's Toxicology: Essentials of Toxicology."

Traditional Toxicologic Research: it is conducted and interpreted by toxicologists which forms the core of risk assessment for chemical exposures.

The four basic components of risk assessment: The National Research Council detailed a framework encompassing hazard identification, dose-response assessment, exposure analysis, and risk characterization, as outlined in "The Red Book." -->

Risk Characterization and Decision Making: Risk assessment involves qualitative and quantitative evaluations, considering exposure, potency of hazardous agents, and uncertainties.

- Risk management integrates multidisciplinary factors.

- Risk communication makes assessment and management information comprehensible to stakeholders.

Woodruff, T.J. (2011)

"The Need For Better Public Health Decisions On Chemicals Released Into Our Environment"

pub hlth protection = children = reduce environmental risk strategies

improvement recs = shift burden of proof away from assumed chem safety without data and update risks for modern knowledge

Tomatis, L et al. (2001)

"Alleged 'misconceptions' distort perceptions of environmental cancer risks"

industrial and synthetic chemicals pose negligible cancer risks, and have flawed assumptions in natural & synthetic pesticide comparison risks.

criticize using animals for human health but do not provide strong enough data information and cannot dismiss original toxicological data