HLTA02 - Week 5

environmental health defintion

Environmental health includes aspects of human health determined by various environmental factors (physical, chemical, biological, social, and psychosocial).

goal of environmental health

Involves assessing, correcting, and preventing environmental factors that could adversely impact health for current and future generations (WHO).

what is the concept of environmental justice

Ensures equal protection and involvement for all people, regardless of race, income, etc., in environmental laws and policies.

what is the objective of environmental justice

Equal protection from environmental hazards and equal access to a healthy environment for all.

HOW DO WE STUDY ENVIRONMENTAL HEALTH

• Toxicology/toxicity assessment

• Exposure assessment

• Environmental epidemiology

3 parts of toxicty assessment

toxiokinetics
toxicodynamics
population models

what does toxicodynamics focus on

focusses on what happens inside of you

does it have a specifc target
will is bond to a specifc enzyme

what is population model

population response and population synamics

TOXICITY ASSESSMENT -Route of administration

Route of administration (or pathways of exposure) have significanteffect on the toxicity of a chemical

• Toxicity assessment must mimic the "real life" scenario as much aspossible

what are models used for acute exposure used to do

• Discover adverse health effects attributed to the agent

• Observe effects that are directly related to the amount of substance administeredsuch as:
o Lethality (LD50)
o Skin and eye irritation
o Photoallergic and phototoxic reactions

noael

no observed adverse effect level, highest level of chemical that doesnt cause significant harm, last safe dose

Classic animal models:

o Many species (e.g. mice, rats)

o Include a control group

what does regulatory toxicology do

• Setting rules and assuring compliance- Product registration- Allowable concentrations in food or environmental media

• Technical and legal issues- Risk and safety are estimated by total weight of evidence- Toxicity evidence is the basis, but rules are modified by political, legalconsiderations, and technical feasibility

• Is the mathematical modeling process that yields estimates for safe or allowablechemical concentrations- Hazard identification- Dose-response and dose-effect assessment- Exposure characterization- Unique effects of chemicals

WAYS TO DEFINE THE EXPOSURE TO AN AGENT

• Questionnaires or interviews• In the environment (e.g., indoor and outdoor air, tap water, soil)

• In human biological samples (e.g., urine, blood, hair, nails)

• Biomarkers of effects (e.g., activity of specific enzyme implicated in themetabolism of a chemical

defining environmental factors

• All non genetic factors

• Factors that are exogenous to human beings

interaction of human population and its characteristics depend on:

• The environment (e.g. physical, socioecomic, biological)

• The agent (e.g. chemicals, contaminants

ECOLOGICAL STUDIES

• Characterize a disease by factors: age, biological sex, time, geographical region, diet

• Examine populations (not individuals)

• Examine the relationships among disease rates and specific exposure

• Use accessible data

• Clues to possible risk factors

• Measure correlations, not causal relationships

OBSERVATIONAL STUDIES

cohort and case control

confounder

Other variables that can be associated with both the exposure and the disease

human health risk assesment

hazard identification

exposure assesment and dose respinse relationship

risk characterizstion

Impact of Climate Change on Agriculture and Food Security

Erratic weather affects crops, food prices increase, poorer populations most affected.

Economic and Resource Inequality from natural disaster

Wealthier people can stock up on resources, have access to private transportation, and can evacuate if needed.

Poorer people typically lack these resources and may risk job loss if they evacuate, making it harder to escape or recover from disasters.

Hurricane Katrina - highlighting disparity

Poor infrastructure and slow emergency response led to ~2,000 deaths, primarily affecting poor, Black Americans.

Health disparities worsened, as more than half of Black survivors lacked health insurance, which impeded access to necessary care.

Long-term mental health impacts, such as PTSD and depression, were prevalent among survivors.

Government and Societal Responsibility in naatural disaster

Governments play a crucial role in disaster response and must prioritize equitable protection for vulnerable populations.

Infrastructure improvements, proper zoning, deforestation prevention, and regulated construction standards are necessary to mitigate risks.

Modern Food Production impact: Intensive, Large-Scale Agriculture

Monocropping: Government-subsidized monocropping of corn and soy in the US degrades soil, necessitating increased use of artificial fertilizers and pesticides, contaminating water bodies and entering the food chain.

Irrigation & Soil Degradation: Heavy irrigation, especially in rice farming, raises soil alkalinity, reduces fertility, and contaminates plants with arsenic (e.g., in Bangladesh and Pakistan).

Modern Food Production impact: Animal Feed

Factory-Farmed Animals: Feeding animals a corn and soy diet, unnatural to them, raises concerns for animal and human health (e.g., high saturated fat content in corn-fed beef).

Dairy: North American cows are often fed grains and treated with hormones, which alters milk composition compared to grass-fed cows in Europe.

Modern Food Production impact: Fish Farming

Pollution & Disease: Factory fish farms pollute water and spread disease to wild fish; artificial foods and chemicals alter the appearance of farmed fish.

Invasive Species Risk: Escapes (e.g., 300,000 Atlantic salmon into the Pacific in 2017) risk ecological impacts on native species.

Lead Toxicity

Accumulates in the body over time; hard to metabolize and excrete.

Lead Toxicity use

Historical Use: Used for pipes in ancient times despite awareness of its toxicity.

Lead Pipes in North America: Still present in water infrastructure, especially older homes, leading to potential lead exposure (e.g., Flint, Michigan, water crisis).

Lead Solder: Present in older copper pipes and pre-1990s infrastructure, leading to exposure through drinking water, particularly in older buildings.

Lead Paint: Common in older homes, where it can degrade into dust, ingested by young children, leading to neurological damage, especially in low-income communities.

Industrial Emissions: Refining and smelting operations release lead into the environment (e.g., Teck Resources smelter in Trail, BC).

Arsenic Pollution:

Widely distributed by human activities like irrigation and mining.

Arsenic Pollution: health risks

Health Risks: Linked to gastrointestinal distress, nausea, heart issues, and cancer, especially in areas with high levels of arsenic in water sources, common in poorer regions.

Household Environment Risks:Chemical Exposure

Canadians absorb significant amounts of chemicals from personal care products, which are not adequately regulated for long-term internal effects. Products like household cleaners and cosmetics may have unknown health impacts when absorbed into the body.

Plastic Pollution:Health Implications:

The long-term effects of micro-plastics on human health are still unknown, but there are concerns about their impact on sensitive biological systems.

Theoretical Considerations:Macro-Level Impacts:

Environmental changes, such as climate change and natural disasters, can affect public health by disrupting food and water supplies, increasing stress, and exacerbating existing vulnerabilities.

what is toxicology and what approach does it use

• Study of adverse effects of chemicals on biological systems
• Interdisciplinary approach

toxicololgy theme

• All substances have the potential to be toxic, but not all compounds areequally toxic!•

what does toxickinetics focus on

how chemicals from from env to inside of you and the outside of you

also focuses on understanding what chemical is and what it looks like, chemical and physical properties

why toxicity assessment

• To determine the effects of a substance on the biological systems

• To assess the safety or hazards of several substance

ld50

amount needed to kill half of the animals in the study

loael

lowest observed adverse effect level, smallest dose that causes significant harm

what is chronic exposure

Long term (half of life expentency), low concentration

what are models used for chronic exposure used to do

Used to:

• Assess the effects of repeated exposure for long periods of time

• Effects observed can be attributed to the accumulation of the substancein the organism.

• Effects measured include: histological alterations of organs and tissues,development of tumors, effects on reproduction, transgenerationaleffects, alterations of fetal development

Alternative animal models

3R (replace animal models, refine animal models, reducethe number of animals used

Polar Region Impact of Climate Change

Greatest temperature increase, affecting Arctic ecology and sea ice melt.

Ocean Impact of Climate Change

Rising sea levels, changing salinity, and ecological disruption in marine life.

Ocean Acidification from Climate Change

Lower pH impacts marine species like coral and shellfish, causing reef collapse.

Insect-Borne Disease and Climate Change

Warmer climates expand range of diseases like West Nile, Lyme, and Zika, affecting health.

Natural Disasters - types

Types: Earthquakes, hurricanes, floods, landslides.

Human modifications (housing quality, poor infrastructure) increase disaster severity.

Impact on Low-Income Communities from natural disasters

Poorer populations are more vulnerable to natural disasters due to inadequate housing and lack of resources.

Importance of Disaster Preparedness

Effective planning, infrastructure investment, and emergency preparedness can significantly reduce fatalities and property damage.

Proactive measures, such as Cuba's evacuation strategy or Florida's improved storm responses, demonstrate the value of investing in disaster management.

Impact: of airpollution

Linked to 7,700 avoidable deaths annually (International Institute for Sustainable Development, 2017).

main source of air pollution

Coal- and oil-fired plants, motor vehicles, domestic and factory heating

Lead in Gasoline

Tetraethyl lead was added to gasoline for engine efficiency from the 1920s and phased out in 1996 due to known toxicity. Lead exposure has particularly affected children living close to busy roads.

Mercury Contamination impact

Environmental Impact: Converts to methyl mercury in waterways, accumulating in fish, especially apex predators (e.g., tuna, swordfish), and leading to mercury poisoning.

Impact on Indigenous Communities: Particularly affects communities relying on fish (e.g., Grassy Narrows, Ontario) due to nearby industrial activity.

Plastic Pollution:Sources of Micro-Plastics:

Common sources include discarded plastic items, micro-beads from cosmetics, synthetic fibers from clothing, and tire wear. These contaminants are found in drinking water across North America.

Acute Exposure

Short-term, high concentration exposure

Impact of climate change

temp rise, sea level rise,
more droughts, more floods, weather affects agriculture, more disease

Hurricane Maria in Puerto Rico - highlighting disparity

Over 60 deaths were recorded, and the U.S. response to assist the predominantly Latino, poorer population was widely criticized for being slower and less comprehensive than for Texas residents in similar conditions.

Toxicologists aims to:

• Understand the mechanisms of toxicity
• Ensure safer chemical and drugs products
• Determine risks from chemical exposure
• Ensure a safe food and water supply

what is exposure assesment

Determines effects of various substances, including routes of exposure and real-life scenarios.

what is environmental epidemiology

• Study of the role of exposures in the environment onthe distribution and determinants of health anddiseases in human populations

• Epidemiological data and toxicological datacomplement each other

• In epidemiology, large sample size and accuratemeasure of exposure are crucial

steps of toxicokinetics

uptake (how you are exposed to it)

biotranfomartion (chemical under gotranformation, broken down)

distribution

elimination (kidney, urine, maybe stay in system )

steps of toxicity asessment

toxicant concentraion in medium

toxicant concentraion in animal

toxicant concentraion at target

toxicant interactiom with target

cellular response

organ response

organism response

population response

type of exposure

acute and chronic

what model can be used to recreate acute exposure

animal and alternative models

what model can be used to recreate chronic exposure

Animal and alternative models

TOXICITY ASSESSMENT: TYPE OF MODELS

Classic animal models:

Alternative animal models

In vitro alternative models

In vitro alternative models

o Episkin: human epiderma constructed from normal humankeratinocytes cultured on a collagen matrix

o Scratch assay: cancer human cell lines to measure theirproliferation

o And many more!!!

TOXICITY DEPENDS ON..

CHEMICAL AND PHYSICAL PROPERTIES
• Of the agent and its metabolites


ENVIRONMENTAL EXPOSURE AND FAT
• Is the agent degraded in the environment (e.g. photodegradation)
• Is the agent in soil, water, air
• Does it accumulate in plants, aquatic animals, terrestrial animals, etc

• Factors that are exogenous to human beings

• Physical (e.g. noise, lighting, radiation)

• Chemical (e.g. contaminants, dust, drugs, tobacco)

• Biological (e.g. bacteria, viruses, parasites)

• Psychosocial (e.g. work patterns, stress, poverty)

• Political (e.g. unsafe water and sanitation)

• Cultural (e.g. gender roles

DIFFERENT DESIGNS for environmental epidemiology

ECOLOGICAL STUDIES

OBSERVATIONAL STUDIES

cohort study

A type of epidemiologic study where a group of exposed individuals (individuals who have been exposed to the potential risk factor) and a group of non-exposed individuals are followed over time to determine the incidence of disease

opp of case control

case control study

A type of epidemiologic study where a group of individuals with the diseases, referred to as cases, are compared to individuals without the disease, referred to as controls

opp of cohort

example of exposure, confounder and outcome

exposure - air pollution
confounder - smoking
outcome - asthma

Environmental health disparities

- proximity to environmental hazzard

- physiological vulnability (old or young age, pregnant)

- the ability to participate in decision

- infustructure

- cumalative environment (smoking, traffic pollution)

- psychosocial stress

risk equation

risk = hazard x exposure

Climate Change

Temperature Rise: Land and sea temperatures have risen about 1°C over the past century, accelerating since 1950.
Caused by CO₂ from fossil fuels, methane from agriculture/industry, and deforestation.

Weather Pattern Changes due to Climate Change

Increased erratic weather, including intense droughts, floods, and storms.

Reef Decline due to Climate Change

Endangers fish habitats and coastlines, contributing to food insecurity.

Food Insecurity and Disease due to Climate Change

Changing marine life and rising temperatures drive northward migration of food fish.

Geographic Disadvantages from natural disasters

Low-income neighborhoods are often located on risky landscapes, like low-lying areas prone to flooding or steep slopes prone to landslides.

Example: In cities such as Houston and New Orleans, low-income neighborhoods often lack adequate storm drainage systems, making them susceptible to flooding.

Hurricane Harvey - highlighting disparity

Similar issues to Katrina, with inadequate drainage in New Orleans, and toxic floodwaters in Houston from oil refineries exacerbating health risks.

Approximately 100 people died, and the long-term environmental impact from polluted water posed further hazards.

Canadian wildfire - highlighting disparity

First Nations people were disproportionately affected due to their proximity to major fires and limited evacuation support.

Government response to remote communities like Wasagamack was criticized for its delayed and poorly organized evacuation.

Hurricane Irma in cuba - highlighting disparity

Despite being a poorer country, Cuba had a well-coordinated evacuation plan, resulting in only 10 deaths among 11.2 million people.

Successful evacuation of 20,000 tourists without injuries highlighted effective government preparation.

Modern Food Production impact: Factory Farming

Pollution: Factory farming pollutes the environment, and causes the spread of pathogens (e.g., swine, avian influenza, BSE, E. coli).

Health Risks: Elevated risks of E. coli, listeriosis, and salmonella infections due to intensive animal farming.

Modern Food Production impact: Manure Contamination

Water Contamination: Animal waste is spread as fertilizer, contaminating water sources with nitrites, E. coli, and other pathogens.

Example - Walkerton Disaster: E. coli contamination from cattle led to 7 deaths and illness for over 2300 people in Walkerton, Canada.

Environmental Impact of Agri-Business

Cheap Food vs. Environmental Costs: Cheap, plentiful food increases dietary choice but raises obesity rates due to high-carb, low-nutrient foods from corn and wheat.

Contamination Risks: Mass production of meat and produce increases risks of pathogen contamination, requiring robust public health monitoring and recalls.

Methane Emissions: Cattle farming is a significant methane source, contributing to greenhouse gases and climate change.

"Dead Zones": Agricultural runoff, like that from Mississippi and Fraser Rivers, causes oceanic dead zones, harming marine life and food fisheries.

fine paticle

tiny particles (2.5 microns or smaller) from vehicle emissions, coal, and wood smoke pose significant health risks. They penetrate the respiratory system and bloodstream, causing systemic health issues.

Gaseous Emissions

Carbon monoxide, nitrogen dioxide, and sulfur dioxide are toxic gases affecting respiratory and cardiovascular he

Heavy Metal Pollution:

lead, mercury, arsenic

Mercury Contamination

A potent neurotoxin and industrial by-product.

Household Environment Risks: Mould and Mildew

High humidity and water infiltration foster mould growth, which can irritate the respiratory system and trigger severe immune responses like asthma, particularly affecting lower-income households living in older, poorly maintained homes.

Household Environment Risks:Indoor Air Quality

Indoor air pollution from cooking and heating appliances can be as harmful as outdoor pollution. Adequate ventilation is often lacking in older homes, contributing to health risks.

Household Environment Risks:Formaldehyde and Flame Retardants:

Common household items off-gas formaldehyde and contain flame retardants, which are linked to health issues, including hormone disruption and decreased fertility.

Plastic Pollution:Ubiquity and Persistence:

Plastics do not decompose but fragment into micro-particles that enter the food chain and the human body. Plastics are often hormone disruptors and can accumulate harmful toxins.

Theoretical Considerations:Cumulative Risk:

Continuous exposure to low levels of contaminants can lead to significant health effects. Interactions between various environmental factors can compound health risks, particularly for vulnerable populations.