Chapter 8 environmental health & toxicology

U.S. && healthcare

- WHO estimates 90% of all disease burden occurs in developing countries - reducing disease burden would help reduce pop. Growth

West nile

- absent until 1999 - family of Mosquito transmitted viruses that cause encephalitis ( brain inflammation)

Ecological disease / emergent disease in humans

- both have in common that environmental change upsets normal ecological relationships

Resistance to antibiotics and pesticides increase

- health workers afraid of wide spread of methicillin resistant staphylococcus aureus - how are Mosquitos and pathogens becoming resistant to pesticides and antibiotics? - bc of natural selection and ability of many organisms to evolve rapidly - another factor is human tendency to use control measures carelessly

largest source of mercury

- is in US from burning coal. -mercury can destroy nerve cells && is dangerous for children . -mercury contamination is the most common cause of lakes and rivers failing to meet pollution regulation standards

metabolic degradation and excretion eliminate toxins

- most organisms have enzymes that process waste products and environmental poisons to reduce their toxicity

Malaria

- most prevalent disease - every year 500 mill cases && one mill people die from this .

hormesis

- nonlinear effect -activating repair mechanisms may defend us from other unrelated effects.

Microbes acquire antibiotic resistance

- repeated exposure and selection many microorganisms and vectors have become insensitive to almost all weapons against them . -

Environmental toxicology

- specifically deals with the interaction, transformation, fate, and effects of toxins in the biosphere including individual organisms pop. And whole ecosystems

Toxicology

- study of adverse effects of external factors on an organism or a system

repair mechanisms mend damage

- tissues and organs that are exposed regularly to physical wear- and- tear or to toxic or hazardous materials often have mechanisms for damage repair -slide 30.

Pathogens

- viruses, bacteria, protozoans, (single called animals) parasite worms, and flukes - worst lost of life from individual disease was influenza pandemic 1918.

Emergent & infectious

-Communicable disease are still responsible for 1/3 of all disease-related mortality - modern life is leading killer everywhere in world .

Largest death toll from emergent disease is due to

-HIV AIDS

endocrine hormone disrupters

-are chemicals that interrupt the normal endocrine hormone functions -DDT PCBS interfere with normal growth, development, physiology of a variety of animals at very low dose.

measuring toxicity

-everything is toxic at very high levels, but can be safe if diluted enough. -basic principle of toxicology -how a material is delivered and at what rate plays a vital role in determining toxicity.

age matters and general health matters

-healthy adults for ex. may be relatively insensitive to doses that are very dangerous to young children or to someone already weakened by other diseases -lead most common toxin in children.

antagonistic reactions

-some materials produce this - they interfere with the effects or stimulate the breakdown of other chemicals

environmental estrogens/ androgens

-these chemicals are called this. they often cause reproductive health problems in females in feminizations of males for example.

movement distribution && fate of toxins

-toxins move back and forth between organisms and the environment -factors affecting toxicity * dose(amount) * route of entry *timing of exposure *sensitivity of organism

chemicals divided into two major groups

-water soluble compounds move rapidly and widely through the environment bc water is ubiquitous - molecules that are oil-or-fat soluble (usually move through the environment and into or within the body.

LD50

A convenient way to describe toxicity of a chemical is to determine the dose to which 50 percent of the test population is sensitive. -iN CASE OF LETHQL DOSE = LD50

Mutagens

Agents such as chemicals and radiation that damage or alter genetic material (Dna in cells)

Conservation medicine

Attempts to understand how our environmental changes threaten our own health as well as that of natural communities on which we depend for ecological services.

Teratogens

Chemicals or other factors that specifically cause abnormalities during embryonic growth and development - ex. Alcohol Can cause fetal alcohol syndrome

Mortality

Death

Sick building syndrome

Headaches, allergies, and chronic fatigue caused by poorly vented indoor air contaminated by various contaminants

Morbidity

Illness

Antibodies

Proteins produced by our bodies that recognize and bind to foriegn cells or chemicals

Neurotoxins

Special class of metabolic poisons that specifically attack nerve cells (neurons)

Antigens

Substances (pollen, bacteria, etc.) recognized by white blood cells and stimulate production of specific antibodies

Allergens / toxins

Substances that activate the Immune system. Some allergens act directly as antigens - toxins taken in small doses can be broken down or excreted before they do much harm.

Carcinogen

Substances that cause cancer Invasive out of control cell growth that result in malignant tumors - cancer now 2nd leading cause of death d

Emergent diseases

Those not previously known have been absent for 20 years

conclusion

We have made marvelous progress in reducing some of the worst diseases that have long plagued humans. However, chronic conditions, that once were confined to richer countries, now have become leading health problems nearly everywhere. New, emergent diseases are appearing at an increasing rate. With increased international travel, diseases can spread around the globe in a few days. In addition, modern industry is introducing thousands of new chemicals every year, most of which aren't studied thoroughly for long-term health effects.

Formaldehyde

Widely used chemical powerful sensitized of the immune system - used in plastics wood products insulation glue - f concentration inside indoor air can be thousands of times higher than normal outdoor air

Ecological diseases

Wildlife experience this widespread epidemic

airborne toxins

cause more ill health than any other exposure source. but food, water, an skin contact can also expose us to a wide variety of hazards.

acute effects

caused by single exposure to the toxin and result in an immediate health crisis -effects can be irreversible

synergism

interaction in which one substance exacerbates the effects of one another.

chronic effects

long lasting, perhaps even permanent. A chronic effect can result from a single dose of very toxic substance, or it can be a result of a continuous or repeated sublethal exposure. - hard to asses bc of other factors, like aging or normal diseases can act simultaneously with the factor under study.

solubility

most important characteristic in determining how where and when toxic material will move through the environment through the body to its site of action

biomagnification

occurs when toxic burden of a large number of organisms at a lower trophic level is accumulated and concentrated by a predator at a higher trophic level.

bioaccumulation

organisms may selectively absorb and store toxins in their bodies

additive

other materials are this - occur together in exposures

risk

the probability of harm times the probability of exposure if that chemical is released into the environment