Environmental Health is defined as those aspects of human health, disease, and injury that are determined by physical, chemical, biological, social, and psychosocial factors.

Environmental health is the branch of public health that is concerned with all aspects of the natural and built environment that may affect human health.

Environmental epidemiology uses observational studies, which simply observe exposures that people have already experienced.

This is because  humans cannot ethically be exposed to agents that are known or suspected to cause disease.

While the inability to use experimental study designs is a limitation of environmental epidemiology, this discipline directly observes effects on human health rather than estimating effects from animal studies.

Toxicology

Risk Assessment

Food Safety

Climate Change

The contaminant source

The contaminated environmental media

The esposure point(s)

The esposure route(s)

The receptor population(s)

All five elements of the exposure pathway must be present for the pathway to be considered completed.

Absorption

Distribution

Metabolism

Excretion

Primary rates of absorption are ingestion, inhalation, and dermal contact.

Secondary rates of absorption are breast milk, transplacental, and intrauterine exposure.

Through the kidney via urine.

Through the liver and GI system via feces.

Through the pulmonary system via exhaled air.

Via breast milk.

Dose response studies help us to understand how much of a toxicant can cause an adverse effect to a specific target tissue.

These studies typcially use animals and occur in controlled conditions.

This action occurs when the combined effect of two or more chemicals is equal to the sum of the effect of each agents given alone (they do not interact in a direct way); for example:

2 + 2 = 4

This effect is the most common when two chemicals are given together.

A biologic response to multiple substances where one substance worsens the effect of another substance.

The combined effect of the substances acting together is greater than the sum of the effects of the subances acting by themselves.

For example: There is a much higher incidence of lung cancer resulting from occupational exposure to asbestos in smokers (compared to exposed non-smokers).

This effect results when one substance that does not normally have a toxic effect is added to another chemical, it makes the second chemical much more toxic.

0 + 2 > 2, not just 2

It is the situation where the combined effect of two or more compounds is less toxic than the individual effects.

Antagonism is the opposite of synergism.

4 + 6 < 10

Antagonistic effects are the basis of many antidotes for poisonings or for medical treatments. For example, ethyl alcohol (ethanol) can antagonize the toxic effects of methyl alcohol (methanol) by displacing it from the enzyme that oxidizes the methanol.

Environmental contamination of mercury has resulted from mining and excavating/melting medals. 

Mercury forms microorganisms in aquatic systems, accumulates in fish, and effects pregnant women. 

Common in agricultural areas due to the use of nitrogen-based fertilizers and proximity to animal handling facilities. 

Nitrates in surface waters can stimulate algae growth, which ultimately increases biochemical oxygen demand (BOD) and depletion of dissolved oxygen. This makes run-off too rich, and animals may die. It can lead to babies not getting enough oxygen in their brain. 

Carbon Monoxide

Sulfur Dioxide

Nitrogen Dioxide

Particulates

Oxone

Lead

Reduces oxygen delivery to body tissues -- especially the brain and heart.

The health effects are most serious for those with pre-existing cardiovascular conditions.

Leads to adverse respiratory effects, such as asthma symptoms and bronchoconstriction.

Especially effects children, the elderly, and asthmatics.

Ozone is a secondary pollutant, formed when nitrogen oxides carbon monixide, and other volatile organic compounds (VOCs) react in the atmosphere in the presence of sunlight.

It can cause airway irritation, coughing, wheezing, and difficultuy breathing. 

Radon is the second leading cause of death from lung cancer.

Geographic areas with greater concentrations of granite rock have an increase risk for radon exposure. 

Radon is a gas that easily diffuses into living area from the soil. It can be inhaled into the lungs.

The toxic effects of ultraviolet light are generally related to direct exposure to the skin and eyes. 

UV-B is the main wave length range that causes damage.

Non-melanoma and malignant melanoma have been associated with exposures to UVR (ultraviolet radiation).

Traditional:Restaurant/food inspection

Sewage system reviews

Rodent and animal control

Water hygiene

Newer:Housing safety

Hotel inspections

Recreational water facility inspections

Flocculation, sedimentation, filtration, and disinfection.

Flocculation is when fine particulates clump together so that they can be filtered out of the water.

Primary treatment involves separation of course objects.

Secondary treatment is the digestion of the sewage by microorganisms. This occurs in a large basin.

Th next step is the physical removal where the microbes and larger particulates are allowed to clump together nad settle. A third process sometimes treats the sewage.

The wastewater is then disinfected and discharged into receiving water. 

The waste sludge from the primary and secondary treatment processes, after dewatering, is usually deposited into landfills, incinerated, or further disinfected.

When it is inhaled, it causes an inflamatory lung disease called silicosis. 

It has histoically been reported among miners, quarry and stoneworkers, sandblasters, and others. 

It is charactered by nodular lesions in the mid/upper lungs. If you have it, you have a higher risk for devloping TB. 

The Federal Meat Inspection Act and 

The Pure Food and Drug Act.

Both were in 1906.

OSHA establishes regulatory exposure levels (Permissible Exposure Limits - PELs) and has regulatory inspection authority to help assure a safe and healthy workplace.

NIOSH conducts non-regulatory health hazard evaluations, conducts epidemiolgy, industrial hygiene, and toxicological research, and develops Recommended Exposure Limts (RELs).  NIOSH also conducts research in worker safety, occupational lung disease, and reporatory protection. They are in charge of regulatory responsibilities for mine and safety health.

Clean Water Act was passed to protect the environmental quality of the water, which is important because most drinking water is derived from surface water sources.

The Safe Drinking Water Act required routine testing of public drinking water supplies.

Also known as the Resources Conservation and Recovery Act (RCRA). It is referred to as the "cradle to grave" law for toxic substances.

Under this law, hazardous materials are tracked from manufacture, through use, to final disposal or recycle processing. 

Also known as The Superfund. 

It is a federal program to provide regulatory oversight and funding to address uncontrolled hazardous waste sites. The legislation provided for a system of identifying, assessing, and cleaning of sites by the EPA.

Hazard Identification (identifying contaminants and exposures which may cause a health hazard)

Dose-Response Evaluation (A quantitative determination of the relationship between exposure to a toxicant and disease).

Exposure Asssessment (A quantitative estimation of the magnitude, duration, frequency and tiing of an exposure to the toxicant of concern).

Risk Characterization (Integrates the first three components of risk assessment to estimate the risk.)

Carciogenic risk assessments use probabilistic models

Non-carcinogenic risk assessments use reference levels such as the EPA's Reference Dose or the ATSDR's (Agency for Toxic Substances and Disease Registry) Minimal Risk Levels.

NIOSH (National Institute for Occupational Safety and Health), part of the CDC...

And ATSDR (the Agency for Toxic Substances and Disease Registry).

They are used to guide land-use decisions and community design from a public health perspective.

Steps include:

1. Screening to determine the usefulness of conducting the HIA.

2. Scoping to identify the health effects of concern, assessing risk and benefits.

3. Making recommendations, reporting the findings, and evaluating how the HIA affected the ultimate decison.