Health & Environmental Risks

Human Health Hazards1. 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)

Toxin Organism

Dose Age

Solubility (water or fat)

How frequently exposure occurred

Persistence Genetic 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

Dose Metric Approx

amount of water

ppm mg/kg1 tsp per 1000

gal

ppb g/kg1 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 . . .

* LD50 – Lethal Dose at which the toxin kills 50% of the organisms

Threshold level:

LD50:

Poisons are toxins that have an LD50 of 50 mg/kg or less. Would the toxin

represented above be a poison?

Toxicity LD50 Lethal Dose Examples

Super < 0.01 less than 1 drop dioxin, botulismmushrooms

Extreme <5 less than 7 drops heroin, nicotine

Very 5-50 7 drops to 1 tsp. morphine, codeine

Toxic 50-500 1 tsp. DDT, H2SO4, Caffeine

Moderate 500-5K 1 oz.-1 pt. aspirin, wood alcohol

Slightly 5K-15K 1 pt. ethyl alcohol, soaps

Non-Toxic >15K >1qt. water, table sugar

(LD50 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.

* ED50 – Effective Dose at which the toxin causes 50% of the organisms to display harmful but not lethal effects.

2. EpidemiologyStudy 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 HazardsAnything 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 LD50 & 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