Environmental Health and Toxicology

Environmental health is defined by the World Health Organization as :

Those aspects of human health and disease that are determined by factors in the environment. It also refers to the theory and practice of assessing and controlling factors in the environment that can potentially affect health.

Environmental health addresses all the physical, chemical, and biological factors external to a person, and all the related factors impacting behaviours.

Health is a state of complete physical, mental, and social well being, not merely the absence of disease or infirmity.

Environmental health concerns….

1. Air quality, including both ambient outdoor air and indoor air quality, which also comprises concerns about environmental tobacco smoke.

2. Body art safety, including tattooing, body piercing and permanent cosmetics.

3. Climate change and its effects on health.

4. Disaster preparedness and response.

5. Food safety, including in agriculture, transportation, food processing, wholesale and retail distribution and sale.

6. Hazardous materials management, including hazardous waste management, contaminated site remediation, the prevention of leaks from underground storage tanks and the prevention of hazardous materials releases to the environment and responses to emergency situations resulting from such releases.

7. Housing, including substandard housing abatement and the inspection of jails and prisons.

8. Childhood lead poisoning prevention.

9. Land use planning, including smart growth.

10. Liquid waste disposal, including city wastewater treatment plants and on-site waste water disposal systems, such as septic tank systems and chemical toilets.

11. Medical waste management and disposal.

12. Noise pollution control.

13. Occupational health and industrial hygiene.

14. Radiological health, including exposure to ionizing radiation from X-rays or radioactive isotopes.

15. Recreational water illness prevention, including from swimming pools, spas and ocean and freshwater bathing places.

16. Safe drinking water.

17. Solid waste management, including landfills, recycling facilities, composting and solid waste transfer stations.

18. Toxic chemical exposure whether in consumer products, housing, workplaces, air, water or soil.

19. Vector control, including the control of mosquitoes, rodents, flies, cockroaches and other animals that may transmit pathogens.

Major sources of environmental health….

1. Toxins – smoking, chemicals, leads

2. Infectious agents – bacteria, protozoa, viruses

3. Trauma – accidents

4. Pollution – noise, air, water

5. Radiation – ionizing, UV

TOXICOLOGY :

Toxicology (from the Greek words toxicos and logos) is the study of the adverse effects of chemicals on living organisms.

1. The study of symptoms, mechanisms, treatments and detection of poisoning, especially the poisoning of people.

2. There are various specialized subdisciplines within the field of toxicology that concern diverse chemical and biological aspects of this area.

3. Aquatic toxicology, Chemical toxicology, Ecotoxicology, Environmental toxicology, Forensic toxicology, and Medical toxicology.

ENVIRONMENTAL TOXICOLOGY : Uses both basic and applied scientific knowledge to understand natural and anthropogenic pollutants life cycle and their impacts upon structure and functions of biological and ecological systems.

l • Release of pollutant into the environment
• Transport and fate into biota (with/out chemical transformation)
• Exposure to biological and ecological system
• Understanding responses and/or effects (molecular to ecological systems)
• Design remediation, minimization, conservation, and risk assessment plans to eliminate, prevent or predict environmental and human health pollutions situations.

2. Hazardous and toxic substances - chemicals present in the workplace which are capable of causing harm.

3. Includes dusts, mixtures, and common materials such as paints, fuels, and solvents.

4. OSHA currently regulates exposure to approximately 400 substances.

The OSHA Chemical Sampling Information (CSI) file contains listings for approximately 1500 substances; the Environmental Protection Agency’s (EPA’s) Toxic Substance Control Act (TSCA) Chemical Substances Inventory lists information on more than 62,000 chemicals or chemical substances; some libraries maintain files of material safety data sheets (MSDS) for more than 100,000 substances.

Solubility and Mobility:

Solubility = important characteristics in determining how, where and when toxic material will move through environment and body

Chemicals can be divided into two major groups:

1. Water-soluble compound – move rapidly and widely through environment

2. Fat-soluble – need a carrier to move through the environment

Exposure and Susceptibility:

There are many routes for entry of dangerous substances into body

1. Airborne toxins – cause more ill health than any other exposure cause

2. Food, water and skin contact – expose human to a wide variety of toxins

3. Industrial settings – workers may encounter doses thousands of times higher than would be found anywhere else

Bioaccumulation and Biomagnification:

Bioaccumulation

- Selective absorption and storage of a great variety of molecule

- Cells accumulate nutrient and essential minerals

- Harmful substances also can be absorbed and stored through the same mechanism

- Toxins can reach dangerous levels inside cells and tissues through bioaccumulation

Biomagnification

- Effects of toxins can be magnified in the environment through food webs

- Biomagnification occurs when the toxic burden of a large numbers of organism at a lower trophic level is accumulated and concentrated by predator in a higher trophic level

Persistence :

- Some chemical compounds are very unstable and degrade rapidly under most environmental conditions

- Most modern herbicides and pesticide quickly lose their toxicity

- Other substances are more persistent and last for years or even centuries in the environment

- This stability also causes problems because these materials persist in the environment and have unexpected effects

Minimizing Toxicology Effect:

- There are 2 mechanism for minimizing toxicology effect :

1. Metabolic Degradation and Excretion

2. Repair Mechanism

Metabolic Degradation and Excretion:

• Every material can be poisonous under some conditions.

• Most organism have enzymes that process waste products and environmental poisons to reduce their toxicity.

• In mammals, the enzymes are located in the liver.

• Liver is the primary site for detoxification of both natural wastes and introduced poisons.

• Besides, we also reduce the effect of waste products and environmental toxins by eliminating through excretion.

• Volatile molecules such as carbon dioxide , hydrogen cyanide and ketones, are excreted via breathing.

• Some excess salts and and other substances are excreted in sweat.

Kidney play an important role in excretion

Repair Mechanism:

• Individual cells have enzymes to repair damage to DNA and protein at the molecular level

• Tissues and organs that are exposed regularly to physical wear-and-tear or to toxic often have mechanisms for damage repair.

• Tissues and organs - high cellular reproduction rates replace injured cells - down side: tumors, cancers possible.

Measuring Toxicity:

Animal testing

- Most commonly used

- Expensive. Why?

1. Hundreds of thousands of dollars used to test one toxin at low doses

2. Time consuming

3. Often very inhuman

4. Difficult to compare toxicity of unlike chemicals or different species of organisms

5. Toxicity between on cat and human are not the same

What is a dose-response curve ?

Dose-response curves can be used to plot the results of many kinds of experiments.

The X-axis plots concentration of a drug or hormone.

The Y-axis plots response, which could be almost anything. For example, the response might be enzyme activity, accumulation of an intracellular second messenger, membrane potential, secretion of a hormone, heart rate or contraction of a muscle.

The LD-50 Test:

The LD-50 test is used to measure the acute toxicity levels of certain ingredients on live animals.

LD-50 stands for Lethal Dose 50 Percent - the amount or concentration of a substance that will kill half of a test group of animals within a specified time period when that substance is forcibly ingested, inhaled or otherwise exposed to an animal. This does not mean 50% died but 50% survived!

During the test period, the animals typically suffer acute distress - pain, convulsions, discharge, diarrhea and bleeding from the eyes, nose and mouth. At the end of the test period, those animals who have not already died (the 50% that survived) are then killed and their organs are examined.

Acute vs Chronic Doses & Effects

Acute:

- immediate health effect

- caused by single exposure to a toxin

- long lasting or permanent health effect

Chronic :

- caused by: a single exposure to a very toxic substance

- continuous or repeated sub lethal exposure to a toxin

Risk Assessment and Acceptance

Risk is the potential harm that may arise from some present process or from some future event.

Risk assessment is the process of estimating the potential impact of a chemical, physical, microbiological or psychosocial toxic on a specified human population or ecological system under a specific set of conditions and for a certain timeframe.

Accepting risks - we go to great lengths to avoid some dangers, while gladly accepting others

Establishing public policy

In setting standards for environmental toxins, we need to consider:

1. The public by using the best science, taking responsive public health actions, and providing trusted health information to prevent harmful exposures and disease related to toxic substances.

2. For protecting the health and safety of people, at home and abroad, providing credible information to enhance their health decisions.

3. Combined effects of exposure to many different sources of damage

4. different sensitivities of members of the population

5. effects of chronic and acute exposures

To protect the public health by helping safe and effective products reach the market in a timely way, and monitoring products for continued safety after they are in use