Environmental Health Overview

Defining the Environment

• Environmental Health Professionals must understand the environment from the perspective of the human body.
• The human body has three main protective barriers: the skin, the gastrointestinal tract, and the membranes in the lungs.

Personal versus Ambient Environment

• People have more control over their personal environment than the ambient environment.
• Personal environment factors include:
  • Hygiene
  • Diet
  • Exercise
  • Tobacco use
  • Sexual practices
  • Drug use
  • Alcohol use
  • Frequency of medical checkups
• The personal environment accounts for around 70% or more of cancer deaths in an industrialized society.

Environmental Forms

• The environment can be categorized into three forms:
  • Gaseous
  • Liquid
  • Solid
• Pollution affects each form.
• Particulates and gases are released into the atmosphere, sewage and liquid wastes are discharged into water, and solid wastes are disposed of on land.

Environmental Impact Mechanisms

• Environmental impact on health can be categorized into four avenues:
  • Chemical constituents and contaminants: toxic wastes, pesticides, chemicals used in homes and industries.
  • Biological contaminants: disease organisms in food, water, insects, animals, and person-to-person contact.
  • Physical contaminants: radiation, noise, vibration, extremes of temperature.
  • Social and psychological factors: stress, lack of access to healthcare, poverty.

Biological Contaminants

• Tetanus: Caused by the bacterium Clostridium tetani, an anaerobic bacterium that produces a toxin called tetanospasmin. Symptoms include muscle spasms, starting in the jaw and progressing to the rest of the body.
• Endotoxins: Released by gram-negative bacteria when they lyse. Can cause inflammation in the respiratory tract, fever, inflammation, and low blood pressure. Symptoms include headache, fever, chest tightness, decreased lung function, cough, and general malaise.
• Fungal toxins: Produced by fungi and can't be made nontoxic by cooking or freezing. Can cause gastrointestinal effects, disulfiram-like effects, neurotoxic effects, and cytotoxic effects.
• Mycotoxins: Toxic secondary metabolites produced by fungi, capable of causing disease and death in humans and animals. Associated with increased incidence of esophageal cancer. Major groups include aflatoxins, trichothecenes, and ergolines.
• Algal toxins: Cyanobacteria, also known as blue-green algae, produce toxins harmful to animals and humans. Responsible for animal deaths from consuming contaminated water. Types of algal toxins include dinoflagellates, diatoms, and cyanobacteria.
• Red tides: Occur when certain species of dinoflagellates bloom, causing reddish-orange discoloration of coastal water. Associated with massive fish and bird kills.

Higher Plant Toxins

• Many plants produce harmful substances that can cause injury or death if ingested.
• Shellfish poisonings are classified into four main categories:
  • Amnesic shellfish poisoning
  • Diarrheic shellfish poisoning
  • Neurotoxic shellfish poisoning
  • Paralytic shellfish poisoning

Environmental Pollutants

• Environmental pollutants are hazardous chemicals released by human activities.
• Pollutants can relocate from their source through interface transport processes, like between air and water, air and soil, and soil and water.
• DDT: Originally developed as an insecticide, became infamous for its environmental impact. Used during WWII to control malaria and typhus. While promoted for agricultural and household use, its health effects at low doses are unknown. High doses can cause vomiting, tremors, and seizures.
• The severity of environmental contaminants depends on these factors:
  • Chemical nature
  • Concentration
  • Persistence

Toxicity in a Population

• The toxicity of chemicals to a population depends on factors like:
  • Species
  • Age
  • Gender
  • Exposure route
  • Duration of exposure
  • Chemical form and activity
  • Concentration or dose
  • Bioavailability
  • Primary route of exposure
  • Absorption ability
  • Metabolism
  • Distribution within the body
  • Excretion
  • Presence of other chemicals

Epidemiology

• Epidemiology: the study and analysis of the distribution, patterns, and determinants of health and disease conditions in defined populations.
• Environmental epidemiology: the study of the distribution and environmental determinants of disease.
• It relies on observational studies, "natural experiments," to identify disease causes.
• Environmental epidemiology is crucial for environmental management decision making, as it helps assess and monitor hazards and quantify their health impact.
• Epidemiological study designs include:
  • Cross-sectional studies: provide a snapshot of a population by determining exposures and outcomes at one time point.
  • Cohort studies: identify groups based on exposure and follow them to measure outcomes.
  • Case-control studies: identify groups based on outcomes and retrospectively collect exposure information.
• Longitudinal research can be:
  • Prospective: individuals are followed over time, collecting data as characteristics change. Birth cohort studies are an example.
  • Retrospective: individuals are sampled, and data about their past is collected.

Workplace Hygiene

• Occupational hygiene is responsible for recognizing, evaluating, and controlling workplace hazards.
• Occupational hygienists use science and engineering to identify, evaluate, and control exposures to hazards like chemicals, dust, fumes, noise, radiation, vibration, and extreme temperatures.
• The aim is to understand risks and provide advice to prevent illnesses like cancer, asthma, skin diseases, and deafness.
• Occupational hygienists address a wide range of chemical, biological, and physical hazards.

Occupational Hygiene

• Musculoskeletal problems are increasingly common in today's technological world.
• Occupational exposures include those to airborne contaminants, radiation, light, electric and magnetic fields, infrared radiation, microwaves, heat, cold, noise, barometric pressure, and stress.
• These exposures can interact with each other.
• The workplace can be a source of infectious diseases, including hepatitis B, tuberculosis, influenza, AIDS, and SARS.

Workplace Hazards

• Manufacturing industries often face air contaminants from industrial processes.
• Other common workplace hazards include noise, vibration, ionizing radiation, and bioaerosols.
• Workers need protection from exposures to biological agents and safe working environments, including safe floors, stairs, and comfortable workstations.

Toxic Chemicals

• Toxic chemicals play a significant role in occupationally related diseases.
• Primary portals of entry for toxic chemicals are the skin and respiratory tract.
• Once inside the body, they can affect organs like the liver and kidneys.

Biological Agents

• Bioaerosols in the air of the workplace are an increasingly recognized problem, especially in the healthcare industry.
• Respirable aerosols containing blood are commonly produced during surgical procedures in operating rooms.