Environmental Health Overview

Overview of Environmental Health

• Environment in environmental health refers to the physical context, from immediate surroundings to the global scale.
• Environmental health is a multidisciplinary public health field.
• It explains the effects of interconnected natural and built environments on health.
• It is an evidence-based framework for minimizing environmental hazards and maximizing environmental benefits.
• Health is defined by the WHO as complete physical, mental and social well-being, not just the absence of disease.

DPSEEA Model

• A spatially explicit WHO model for environmental health interventions.
• Driving Forces are the underlying societal processes that influence environmental health.
• Pressures are hazards introduced to the environment from the driving forces.
• State refers to changes in the environmental condition due to the pressures.
• Exposure is when humans are subjected to the changes in the state of the environment.
• Effects are the health impacts from human exposures.
• Actions are interventions to improve public health at any stage.

Spatial Scale Examples

• Global environmental health issue is climate change.
• Regional environmental health issue is wildfire air pollution.
• Local environmental health issue is urban heat islands.
• Household environmental health issue is lead and asbestos.

Ecology and Health

• Ecology is the study of the interconnectedness of living things and their environment.
• Environmental health studies how environments affect humans.
• An ecosystem includes living (biotic) and nonliving (abiotic) components.
• Holism means ecosystem components are interconnected; ecology views ecosystems holistically.
• Emergence means the ecosystem as a whole is greater than the sum of its parts

Biomagnification

• Refers to increasing concentrations of bioaccumulated toxins as biomass moves up the food chain.
• More biomass must be consumed at each trophic level.
• PCBs are synthetic organic compounds that are highly carcinogenic and bioaccumulate in fish, which is the primary exposure pathway for humans.
• DDT is another example of biomagnification.

Biodiversity

• Biodiversity is the variation in life, encompassing genetic variation, phenotypic variation, different life history stages, species, communities, and ecosystems.
• Greater biodiversity means healthier ecosystems.
• Ecosystem services are benefits provided to humans by nature.
• Mangroves provide protection against storm surge and erosion.
• Bee pollination assists the pollination of crops.
• Ecosystem services are foundational to human health because we rely on ecosystems for food and water.

Exponential and Logistic Growth Curves

• Exponential growth is associated with r-selected species: Opportunists like weeds, that experience exponential population growth and produce many offspring.
• Logistic growth reaches a carrying capacity of the environment over time.
• Populations usually hover around carrying capacity.
• K-selected species Grow slowly, produce fewer offspring, and have more parental involvement.

Agricultural Runoff

• Eutrophication refers to the depletion of oxygen in water due to excess nutrients, such as nitrogen and phosphorus, often from agricultural runoff of fertilizers resulting in harmful algal blooms.

Feedback Loops

• Positive feedback exacerbates the initial change, such as stress leading to more sleeplessness and stress.
• Negative feedback diminishes the initial change, such as body temperature increasing, leading to sweating, and body temperature decreasing.

Sustainability

• Refers to creating and maintaining the conditions under which humans and nature can exist in productive harmony to support present and future generations.
• The nested model depicts that the economy requires a just and healthy society, which requires a healthy environment.

Challenges to Sustainability

• Population growth: UN projects 10 billion people by 2050.
• Consumerism: Consumer spending is the main driver of economic growth.

Planetary Boundaries

• Boundaries already exceeded include: climate change, nitrogen cycle, and biodiversity loss.
• Additional key boundaries are chemical pollution, atmospheric aerosol loading, change in land use, and global freshwater use.

Renewable / Non-Renewable Energy

• Renewable energy can be replenished.
• Non-renewable energy cannot be replenished.
• Zero-carbon fuels do not emit carbon.
• Carbon-based fuels emit carbon.

Recycling

• Most plastics are not truly or practicably recyclable with current commercially feasible technologies.
• When a plastic is “recycled,” the resultant plastic is a lower grade plastic.
• A chasing arrows logo on plastic indicates what kind of plastic it is but does not necessarily mean it is recyclable.

Circular Production Model

• Circular production is sustainable, but it is not currently used in virtually any product.

Sustainable Individual Actions

• Traveling longer distances, take a train or bus instead of an airplane.
• Electric vehicles produce less emissions during their full lifecycle though require more energy.
• Reduce consumption, reuse materials, and recycle correctly.

Environmental Epidemiology

• Distributions include statistical and spatial properties of disease and risk factors.
• Determinants are factors that could plausibly affect human health, which can be good or bad.

Exposure

• Exposure refers to anything people are subjected to that could plausibly affect human health.
• Examples include outdoor heat leading to heart attacks and air pollution leading to asthma.

Hill’s Criteria

• Temporal relationship means the exposure must come before the outcome (MOST IMPORTANT).
• Consistency means many different study teams have come to a similar conclusion.
• Biological plausibility means a reasonable physiological cause and effect relationship exists.
• Dose response means more exposure equals more risk.
• Effect size corresponds to a notably higher risk among exposed.

Sufficient-Component Cause Model

• Intervening on the necessary cause is the most efficient way to reduce disease burden.
• Eliminate SARS-CoV-2 to reduce its disease burden.
• Eliminate mercury to remedy mercury poisioning.

Epidemiologic Study Designs

• Descriptive studies describe the distribution and patterns of disease and risk factors.
• Correlational/ecological studies relate population-scale diseases with widespread exposures.
• Clinical trials test the safety and efficacy of medications or other interventions.
• Cohort studies compare disease rates between exposed and unexposed individuals.
• Case-control studies recruit groups with and without a disease and look back in time to calculate exposure odds in both groups.

Randomized Clinical Trial (RCT)

• Randomized clinical trials are rare in environmental epidemiology due to ethical implications.

Necessary and Sufficient Causes

• Identifying a necessary cause is useful for an effective public health intervention.

Geospatial Analyses

• GIS is a geographic information system.

Coordinates

• Conventional formats for coordinates follow the format (degrees E, degrees N).
• Another way of putting this "(long, lat)".

Vector and Raster Data

• Vector data includes points, lines, or polygons.
• Raster data is gridded, pixels = 1 value, files are referred to as “raster image files”.

Toxicology

• Toxicology is important to public health as it establishes physiological pathways and is necessary for biological plausibility.
• Any substance can be toxic at a specific percent.
• LD50 is the dose of a chemical that results in death for approximately 50% of the population.

Public Health Scientist Roles

• Exposure assessor measures the concentration of air pollutants.
• Epidemiologists study cancer prevalence in a community.

PFAS

• Drinking water is the most common way that PFAS is ingested.

Toxicokinetics

• Toxicokinetics is comprised of absorption, distribution, metabolism, excretion.

Persistent Organic Pollutants

• They do not break down easily, and remain in the environment for long periods of time.
• They accumulate throughout the food chain and can cause health problems in humans and wildlife.

Industrial Hygiene Framework

• Anticipation involves identifying potential hazards before they occur.
• Recognition involves industrial hygienists identifying hazards present in the workplace.
• Evaluation includes area sampling, personal sampling, and biological sampling.
• Control involves substitution, ventilation, PPE, and administrative controls.

Sampling Strategies

• Stratified random sampling
• Worst-case sampling is a non-random sample of workers with the highest risk of exposure.

Acute vs. Chronic Exposures

• Acute exposures are short term (seconds to days).
• Chronic exposures occur over a lifetime.

Aggregate vs. Cumulative Exposures

• Aggregate exposure refers to one specific chemical and all the pathways and routes.
• Cumulative exposure refers to total exposure to multiple toxicologically similar chemicals through all pathways and routes.

Environmental Ethics

• Utilitarianism means the ends justify the means, maximizing well-being and minimizing suffering.
• Deontology means duties, appear to authority or laws, known as Kantianism.

Environmental Ethics Paradigms

• Anthropocentrism focuses on human interests.
• Prudential anthropocentrism recognizes that humans depend on the natural environment.
• Zoocentrism focuses on animal welfare.
• Biocentrism focuses on all living things.

Institutional Review Board (IRB)

• IRB approval or formal exemption is required for research involving living persons with the intention to disseminate and contribute to broader knowledge for society.

Clinical Ethics Pillars

• Autonomy: patients have the right to make their own decisions.
• Beneficence: benefit the patient
• Non-maleficence: do no harm
• Justice: fairness

Synthesis

• Ecology: Study of the interactions between organisms and their environment, and how environmental factors affect human health.
• Sustainability: Meeting the needs of the present without compromising the ability of future generations to meet their own needs.
• Epidemiology: Study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems.
• Toxicology: Study of the adverse effects of chemical, physical, or biological agents on living organisms, and how the exposure leads to adverse health effects.
• Industrial hygiene: Science of protecting and improving the health and safety of workers and communities.
• All the above frameworks contribute to the field of environmental health.