Health & Environmental Risks

Human Health Hazards 1. Physical – includes environmental factors such as natural disasters and exposure to UV radiation

2. Biological – includes exposure to pathogenic organisms bacteria that cause cholera

Nontransmissible disease  does not spread from one organism to another ex. Cancer, Diabetes

Transmissible disease  Caused by pathogens and can easily spread from one organism to another using vectors/carriers AKA Infectious disease

Notable infectious diseases * Plague  caused by a bacterium that is carried by fleas

RBCs infected with Plasmodium * Malaria  caused by members of the protozoan genus called Plasmodium. The Anopheles mosquito is the vector.

* Tuberculosis (TB)  caused by a bacterium that primarily infects the lungs and is highly contagious

* HIV/AIDS  viral disease that emerged in the late 1970s

* H5N1  viral disease that emerged in 2006, the carriers are birds. Closely related to H1N1 (bird flu), but much more deadly.

Factors that affect the spread of diseases Travel, migration, deforestation, climate change, loss of biodiversity, agriculture, urbanization, & nature disasters It sure is nice to get away from the colon for awhile

3. Chemical – includes exposure to naturally occurring and synthetic chemicals Toxins … chemicals that cause harm

5 main categories of TOXINS * Neurotoxins – disrupt the nervous system by attacking neurons or interfering with communication between neurons ex. DDT, PCB, dioxins, arsenic, organophosphate pesticides, etc * Carcinogens – cause cancer, uncontrolled mitosis (cell growth) ex. Asbestos, radon, formaldehyde, etc

* Teratogens – chemicals that cause birth defects ex. alcohol, thalidomide (no longer available) * Allergens – chemicals that cause allergic reactions ex. chemicals in peanuts, milk, penicillin

* Endocrine Disrupters – chemicals that interfere with the normal functioning of hormones in an animal’s body. aka Hormonally Active Agents (HAA) ex. atrazine and other pesticides

Response of body to toxin can be…. Acute - immediate reaction OR Chronic - long term effects

Toxicology … study of chemical risks

Toxicity  measure of the harmfulness of a chemical (dependent on toxin and the organism affected) ToxinOrganism DoseAge Solubility (water or fat) How frequently exposure occurred PersistenceGenetic makeup Interactions with other chemicals in the organism Health of detoxification systems

Solubility of a toxin affects how readily it bioaccumulates in an organism and biomagnifies in an ecosystem. Persistence determines how long the toxin remains in the environment.

How do scientists determine the toxicity of a chemical?

1. Dose-Response Studies (bioassays) Expose plants or animals(rats) to different amts of a chemical and observe responses The amount of the chemical is measured by… concentration (amount in air, water or food) or by dose (amount absorbed or consumed by the organism) Usually measure mortality as response

Dose measurements and their equivalents DoseMetric Approx amount of water ppmmg/kg 1 tsp per 1000 gal ppb  g/kg 1 tsp per 1,000,000 gal

graph typically produced by data at the end of a dose response study * Threshold level – maximum point at which toxin does little or no harm The graph can be used to determine... * LD 50 – Lethal Dose at which the toxin kills 50% of the organisms

Threshold level: LD 50 : Poisons are toxins that have an LD 50 of 50 mg/kg or less. Would the toxin represented above be a poison?

ToxicityLD 50 Lethal DoseExamples Super < 0.01less than 1 drop dioxin, botulism mushrooms Extreme <5less than 7 drops heroin, nicotine Very drops to 1 tsp. morphine, codeine Toxic tsp. DDT, H 2 SO 4, Caffeine Moderate 500-5K1 oz.-1 pt. aspirin, wood alcohol Slightly5K-15K 1 pt. ethyl alcohol, soaps Non-Toxic>15K>1qt. water, table sugar (LD 50 measured in mg/kg of body weight)

At times toxicologists do not measure mortality but measure how a chemical may alter behavior. These are sublethal effects. * ED 50 – Effective Dose at which the toxin causes 50% of the organisms to display harmful but not lethal effects.

2. Epidemiology Study of large populations of organisms exposed to chemicals in their everyday life and determines whether these exposures are related to any health problems. CAN BE Retrospective or Prospective (past) (future) ex. Bhopal disaster ex. track a target population & their habits

Environmental Hazards Anything in the environment that can cause harm. pollutants, human activities, natural catastrophes, etc

When policy makers, regulatory agencies, and environmental scientists assess the risk of a environmental hazard, they follow a three step process known as…

1. Risk assessment includes identifying the hazard, determining it’s toxicity and the extent of exposure Risk Analysis

2. Risk acceptance what is acceptable when balanced against social, economic and political considerations According to the EPA, a 1 in 1 million risk is acceptable for most environmental hazards. The EPA takes the LD 50 & divides it by 10 for most animals to determine the safe concentration. Then divided by 10 again for humans.

3. Risk management Determine policy with input from private citizens, industry, and interest groups TSCA – Toxic Substance Control Act FIFRA Regulated by the EPA