AH 3175E Exam 1 Notes

Exam notes for the 10/6/26 exam in AH 3175E. Multiple choice is recommended for learning.

Environmental health

all the physical, chemical, and biological factors external to a person, and all the related factors impacting behaviors. It encompasses the assessment and control of those environmental factors that can potentially affect health. It is targeted towards preventing disease and creating health-supportive environments

Environment

The circumstances, objects, and conditions by which one is surrounded

public health

All that which is external to the individual/host. The environment can be divided into physical, biological, social, and cultural factors – any or all of which can influence health status in populations

Environmental Epidemiology

The study of patterns of illness among human populations and the factors that might be responsible for influencing these patterns. Associations between exposure to environmental agents and subsequent development of disease

Environmental Chemistry

The study of the sources, reactions, transport, effects, and fates of chemical species in water, soil, air, and living environments

Toxicology

The study of the causal mechanisms between exposure and subsequent development of disease.

the study of the adverse effects of chemical, physical or biological agents on living organisms and the ecosystem, including the prevention and amelioration of such adverse effects

Environmental Engineering

The study of factors and implemented strategies that govern environmental quality and reduce exposure to environmental hazards. Understanding exposure assessment scenarios.

Preventive Medicine

Factors and implemented strategies that govern and reduce disease development

Environmental Law

development of appropriate legislation and regulations to protect the environment and public health

Determinants of Health

environmental health challenges

Physical inactivity, Driving, Traffic, Air pollution, Lung disease, Heat Stress, Motor vehicle and Pedestrian Injuries, Water quality, Mental Health

Disability Adjusted Life Year (DALY)

The loss of the equivalent of one year of full health

Leading global causes of DALYs

DALY

Disability Adjusted Life Year

YLD

Years lived with disability

YLL

Years Life Lost

Environmental Agents

Chemicals or factors in the environment to which humans are exposed that may cause adverse health effects

Epidemiology

The study of patterns of illness among human populations and the factors that might be responsible for influencing these patterns. Relies on mathematical computations and statistics to make deductions based on these patterns

disease clusters

A group of individuals develop the same disease in frequency that appears too large to be due to coincidence

Superfund site

Government recognizes contamination in the region and is able to link which people who induced the contamination

Fundamental Assumptions of Epidemiology

Disease does not occur in a vacuum. Disease is not randomly distributed throughout a population. Epidemiology uses a systematic approach to study the differences in disease distribution in subgroups, allowing for the study of causal and preventive factors

Environmental Epidemiology

The study of disease and health conditions occurring in the population that are linked to environmental factors

various study designs of Environmental Epidemiology

Cross-sectional, Ecological, Case-control, Cohort

temporal factors of Environmental Epidemiology

Cross-sectional, Prospective, Retrospective

Cross-Sectional Studies

An “observational” design that surveys exposures and disease status at a single point in time (a cross-section of the population)

Prospective Studies

Looks forward, looks into the future, examines events that occur. Follows a condition, concern, or disease into the future.

Retrospective Studies

Looks backward in time to study events that have already occurred

Ecological Study

Investigates the relationship between health outcomes and exposures at the population level, rather than focusing on individual cases.

Researchers analyze entire groups, defined by characteristics like geography, socioeconomic status, or ethnicity, to see if there are correlations between these groups and the factors of interest

Weakness – while effective for comparing general trends between population groups (e.g., two similar towns, one located near a Superfund Site, one not near contamination) these studies lose the fine-scale data about the individual and other potential compromising/compounding factors

Case – Control Study

An observational design comparing exposures in disease cases versus healthy controls from the same population, Exposure data is collected retrospectively, Most feasible design when the disease outcome is rare

Cohort Study

An observational study that follows a well-defined group of people (the cohort) over time, Researchers are interested in how exposure to a certain factor (risk factor, environmental condition, etc.) influences the development of a specific health outcome (disease, mortality, etc.) within the cohort.

Strengths of Cohort Study

Exposure status determined before disease detection

Subjects selected before disease detection

Can study several outcomes for each exposure

Limitations of Cohort Study

Expensive and time-consuming

Inefficient for rare diseases or diseases with long latency

Difficulty of cohort participant retention to “follow-up” communication issues

Criteria of causal association

Consistency – repeated result from exposure to agent factor

Specificity – specific result from exposure to agent factor

Temporality – cause (i.e., exposure) before effect, Biological gradient – dose-response curve

Plausibility – biologically plausible

Coherence – data should not contradict the knowledge of the disease

Incidence

The occurrence of new disease or mortality within a defined period of observation (i.e., set time period) within a specific population

Prevalence

the measure of disease frequency in the context of the existing cases of disease

Incidence

_________ = # new cases / # of persons at risk

Prevalence

__________ = # of cases present / # persons in the population

Factors Making Environmental Disease Difficult to Identify

Latency

Multi-factorial etiology

Disease non-specificity

Individual characteristics

Changes in response with changing dose

Mixed exposure

Latency

Long period of time between exposure and response

requiring lengthy follow-up (e.g., 20 – 25 years for certain cancers)

Multi-factorial etiology

Multiple factors influence the occurrence & severity of disease

Disease non-specificity

Most diseases have multiple causes besides environmental agents, though the disease “looks” the same however it was produced

Individual characteristics

Susceptibility (genetic factors) & effect modifiers (e.g., diet, habits, health, medications)

Changes in response with changing dose

Because of data collection processes, dose-response relationships are not accounted for in grouped epidemiological studies, leading to cohorts with heterogeneous exposure levels

Mixed exposures

Multiple agent exposures produce multiple diseases and synergisms

Molecular epidemiology

Incorporation of biomarkers into analytic epidemiologic research

Biomarkers

Chemical or cellular alterations that are measurable in biological media, such as human tissues, cells, or fluids

Biomarkers of Internal Dose

Direct measurement of toxic chemicals or their metabolites in cells, tissues, or body fluids

Biomonitoring

The utilization of biomarkers in the measurement of the body burden of toxic chemical compounds, elements, or their metabolites in biological materials

Exposome

the measure of cumulative environmental influences and associated biological responses throughout lifespan, including exposures from the environment, diet, behavior, and endogenous process

External exposome

sensor technologies now exist that capture pollutants, Exercise, Stress, Circadian thythms, Location, Air/water sampling with analysis by mass spectrometry

Environmental Toxicology

Allows the prediction of chemical toxicity and the synthesis of non-toxic

analogs

Elucidates the routes of selective toxicity

Details the cause and progression of disease state

Enables the design of antidotal therapies

Assesses health risk and informs regulatory limits

Informs care providers while monitoring exposed populations

Adverse effects

Damages to either the survival or normal function of the individual.

Xenobiotic

A chemical compound (e.g. pesticide, drug, or carcinogen) that is foreign (Greek ____) to a living organism.

Toxicant

Substances that produce any adverse biological effects of any nature. Must be chemical or physical in nature.

Toxin

Specific molecules and proteins that are produced by living organism (e.g. mushroom toxin)

Poison

Toxicants that may cause death or illness in very small amounts.

Additive

simple combination of components. 1 + 1 = 2

Antagonistic

one acts nullify the other, which can be protective or harmful. 1 + 1 = 0

Coalitive

agents acting together have a toxic effect, individually do not 0 + 0 = 1

Potentiating

one makes the other have a stronger effect 0 + 1 = 1

Synergistic

combination is more than additive. 1 + 1 > 2

Dose

The quantity of the substance received by the organism at one time.

Toxicity Dependents

Dose

Type of Substance

Frequency of Exposure

Organism

Administered or applied dose

The amount presented to an absorption barrier and available for absorption

Does not necessarily mean having yet crossed the outer barrier/boundary of the organism

Absorbed dose

The amount crossing a specific absorption barrier through uptake processes

Example barriers include skin, lungs, and digestive tract

Internal dose

A more general term denoting the amount absorbed without respect to specific absorption barriers

Gram

typical unit used to express dose

Body weight

For both “effective dose” and “toxic dose” studies, doses are standardized based on ______

Median Lethal Dose (LD50)

The Benchmark of Toxicity

Dose – Response Relationship

The link between the amount of a substance an organism is exposed to (the dose) and the biological effect it has (the response)

Can establish the lowest dose where an objectively measurable effect first occurs (threshold level)

Establishes a quantitative relationship between the dose and the response

Provides the basis for establishing a causal relationship between the dose and the response

Provides information to assess the relative toxicity of a chemical when compared with others tested under similar conditions of exposure

No Observed Adverse Effect Level (NOAEL)

Highest dose where there is not an observed toxic or adverse effect

Lowest Observed Adverse Effect Level

Lowest dose at which there is an observed toxic or adverse effect

Dose-Response Curve

Threshold dose

The lowest dose that produces an (adverse) effect

slope of a dose

The part of the response curve that rises most rapidly, representing the change in response intensity per unit increase in dose.

Therapeutic Index

LD50/ED50E

Effective Dose

ED

Lethal Dose

LDT

Toxic Dose

TD

Dose-Response Relationship

What is the relationship of this graph

True

True or False, a dose can be a single event

False

True or False: a dose can be a one time multiple event

Continuous

What type of exposure-time scenario is this?

Intermittent

What type of exposure-time scenario is this?

Cyclic

What type of exposure-time scenario is this?

Random

What type of exposure-time scenario is this?

Concentrated

What type of exposure-time scenario is this?

_________ = Intensity x frequency x duration

What is the equation for exposure?

Scientific Validity of Toxicilogy

What are these a standard for?

1. A method is needed to objectively measure an adverse response.

2. The adverse response occurs after the dose is administered.

3. The adverse response is due solely to the dose.

4. The type of adverse response(s) measured is the same or similar

for each individual or in vitro (meaning “within glass,” term used for

cellular studies) system that is used for testing.

5. The intensity of the adverse response is proportional to the dose.

in vivo

What is the latin definition for laboratory animal studies

in vitro

What is the latin definition for cellular assays

Toxic effects of an agent

What determinants are these for?

• The nature of the hazardous agent

• The dose or quantity to which the individual is exposed

• The pathway(s) of exposure

• The pattern of exposure

• The duration of exposure

Uncertainty factors

Used to account for species difference, human-to-human variability, and study design parameters

reference dose

maximum acceptable oral dose of a toxic substance, below which no adverse non-cancerous health effects should result from a lifetime of exposure

RfD

What is this equation for?

Threshold Dose Response - RfD Determination

What graph is this?

Acute, Subacute, Subchronic, Chronic

What are the four basic types of exposure duration?

Natural (Biological, Physical, Chemical), Anthropogenic (Chemical, Physical)

What are some Sources (Agents) of Environmental Exposure?

Vectors (Air, water, food, soil)

What are some Transporters & Fates of Environmental Exposure?

Dose to Target, Susceptibility, Effect, Continuum

What are some Health Effects of Environmental Exposure?