a closer look at types of biological and chemical hazard

A Closer Look at Types of Biological and Chemical Hazard

Bio-hazardsBacteria

– single celled organisms (lack nucleus)– if they are parasites, they are classed as pathogens– can survive outside of a human body (host organism)– can form spores (dormant structures) that can survive millions of years– reproduce by asexual reproduction (mitosis)

Bio-hazardsViruses - much smaller than bacteria (cannot

be seen with a light microscope) - are not cells therefore not

considered quite “alive” - DNA inside a protein shell - can only replicate inside living cells - usually require direct contact for

transmission but can survive briefly in the air (e.g. sneezing/ coughing)

Bio-hazardsFungi - includes moulds, yeasts,

mushrooms - can reproduce by dispersing

spores - most grow thread-like hyphae to

draw in nutrients - can produce mycotoxins - “black mould” in houses - allergies can be severe

Black Mold

Bio-hazardsProtozoans (or Protists) - single celled organisms (more

complex than bacteria) - e.g. DNA is inside a nucleus - diseases include dysentery (E.

coli), malaria, African sleeping sickness

Bio-hazardsWorms - roundworms, tapeworms,

flatworms - often infect people through

undercooked food, infected water, skin contact with larva in soil

Chemical HazardsContaminant – a chemical in an ecosystem that is normally not

presentPollutant – a contaminant that

causes damage within an ecosystem Toxin – a pollutant that poses a

human health riskToxicology – the study of health

effects of chemicals

Six basic types of chemical hazard1. Mutagens- Cause changes to genetic code in

the DNA of organisms (mutations)- May (or may not) lead to disease

Six basic types of chemical hazard

2. Carcinogens

- Cancer causing- Uncontrolled cell division

(mitosis) leads to a mass of cells called a tumour or carcinoma.

- Tumours block normal function of other tissues

3. Teratogens- Any agent (chemical, biological or

physical) that can cause a malformation of a fetus; a birth defect.

- Route of entry is placental transfer (from the mother’s blood to the fetus)

- Examples: alcohol, nicotine, aspirin, mercury, lead, measles, chickenpox, x-rays etc.

- Example: thalidomide 1957-1961 sold as a sedative drug to pregnant women (and to aid with ‘morning sickness’). Banned in the mid 1960s (limb deformities)

Fetal Alcohol Syndrome

Thalidomide

4. Allergens- Immune system

over-reacts to a chemical and causes a response greater than necessary (increased production of white blood cells).

- Increased asthma may be a result of more synthetic chemicals present

Increase in Asthma

5. Neurotoxins- Attack the nervous system- Can cause slurred speech, loss of

muscle control, death- E.g. heavy metals such as mercury,

snake and frog venom

6. Endocrine Disruptors- Interfere with the endocrine system

(production of hormones or messenger molecules – such as testosterone and estrogen)

- Possible link to rise in breast cancer, low birth weights, early puberty

- Examples – DDT, softening chemicals in plastics, lead