Environmental Health: Solid Waste, Water Quality, and Food Safety
Week 10: Solid and Hazardous Waste
What is Solid Waste vs. Hazardous Waste?
- Solid Waste: Any unwanted or discarded material we produce that is not a liquid or a gas, such as packaging, appliances, organic materials, food waste, paper, and electronics.
- Hazardous Waste: Poses a threat to human health or the environment due to its poisonous, chemically reactive, corrosive, or flammable nature. Examples include industrial solvents, hospital medical waste, car batteries, household pesticide products, dry-cell batteries, and ash from incinerators and coal-burning power plants.
Trends in Solid Waste Production
Municipal solid waste (MSW) has been increasing over time.
Methods for Source Reduction of Solid Waste
Prioritizing waste reduction involves various strategies:
- Reduce packaging materials
- Make products last longer
- Reuse, repair, and recycle
- Compost organic materials
- Buy reusable/recyclable products
What is Source Reduction?
Source reduction is the practice of minimizing waste generation at its origin, which is the most environmentally preferred approach.
Importance of Recycling
Recycling offers numerous benefits:
- Reduces greenhouse gas emissions
- Prevents pollution associated with new material production
- Decreases landfill waste
- Conserves natural resources
- Creates manufacturing jobs
- Saves energy
Landfills for Solid Waste Disposal
How Landfills Work
Landfills are designed to contain waste and prevent environmental contamination:
- A clay and plastic liner at the bottom prevents leaks of hazardous materials.
- A flexible membrane liner further contains toxic chemicals.
- A leachate sump collects and treats liquids from the landfill.
- Garbage is compacted and covered with soil daily.
- Anaerobic bacteria decompose organic materials, producing methane gas.
Megafills
Megafills are large-scale landfills that handle 5,000-10,000 tons of trash per day, serving regional waste disposal needs. They are often more cost-effective than incinerators.
Week 11: Water Quality and The Future of Energy
The Hydrological Cycle
The hydrological cycle describes the continuous movement of water on Earth:
- Water evaporates from the ocean.
- Water vapor condenses to form clouds.
- Moisture returns to the surface as precipitation.
Surface Water vs. Groundwater
- Surface water: Naturally open to the atmosphere, such as rivers, lakes, streams, ponds, and oceans. It tends to be more susceptible to pollution.
- Groundwater: Stored below ground in aquifers and generally cleaner than surface water.
Human Impact on Water Quality and Quantity
Quantity
Human activities can alter water quantity through:
- Hydrology changes: Construction of dams, levees, culverts, and canals to redirect water flow and manage floods.
- Reservoirs: Built for water storage.
- Pumping: Groundwater extraction for agriculture, industry, and drinking water.
Chemical Contamination
Chemical contamination can occur through:
- Point source pollution: Direct discharge from a specific source, such as an industrial pipe or lagoon.
- Non-point source pollution: Runoff from a broad area, like parking lots, urban areas, and agricultural fields.
Routes of Exposure to Microbial Agents
Exposure to microbial agents in water can occur through:
- Ingestion: Drinking or cooking with contaminated water.
- Dermal absorption: Bathing in contaminated water.
- Inhalation: Breathing in volatile organic chemicals while showering.
The Global Burden of Waterborne Disease
Waterborne diseases pose a significant health burden worldwide.
US Regulatory Framework for Water
The Clean Water Act (1972)
Regulates pollution discharges into natural water bodies to protect aquatic and human health. It requires sewage treatment and permits for industrial waste discharge.
The Safe Drinking Water Act (1974)
Sets standards for contaminants in drinking water to protect human health. It establishes Maximum Contaminant Level Goals (MCLGs) and enforceable Maximum Contaminant Levels (MCLs).
Week 13: Food Safety
Foodborne Disease
Foodborne disease refers to illness caused by consuming contaminated food. Common causative agents include:
- Salmonella
- Escherichia coli
- Norovirus
- Pesticides
Outbreak vs. Cluster
- Outbreak: Two or more cases of a similar illness linked to a common source.
- Cluster: A higher than expected number of cases in a specific geographical area.
Outbreak Investigation Team
An outbreak investigation team typically includes:
- Epidemiologist: Analyzes data to identify the source of the outbreak.
- Public health nurse: Interviews patients to gather information about their symptoms and potential exposures.
- Lab investigator: Interprets test results to identify the causative agent.
- Environmental health investigator: Focuses on food handling practices and potential environmental sources of contamination.
Other Causes of Food-Related Illness
- Heavy metals (e.g., lead) can leach into food and cause vomiting.
- Antimicrobials in food can contribute to antibiotic resistance.
- Food additives and preservatives can cause adverse reactions in some individuals.
Regulation of Food
Roles of FDA and USDA
- Food and Drug Administration (FDA): Regulates and enforces food safety in the US.
- US Department of Agriculture (USDA): Regulates the safety of meat and poultry products.
Delaney Clause
Prohibits the use of food additives, including pesticides, that have been shown to cause cancer in humans or animals.
Significant Food Safety Regulations
- 1906 Food and Drugs Act
- The Federal Food, Drug, and Cosmetic Act of 1938
- Miller Pesticide Amendments, 1954
- Food Additives Amendment, 1958
- Color Additive Amendments, 1960
- Animal Drug Amendments, 1968
- Food Quality Protection Act (FQPA), 1996
Occupational Health
Occupational health focuses on promoting and maintaining the well-being of workers by preventing health risks, controlling hazards, and adapting work environments to protect employees.