IB-1 Principles of Chemical Control Toxicology & Epidemiology

Question 0

Powders inhaled can enter the respiratory tract and deposit in 3 areas - nose / respiratory tract / alveoli.

For each area state the amount of microns needed for powder to deposit and the body’s mechanisms used to defend against these

Answer 0

• Nasal cavity anything above 10 microns. Defences include - nasal hairs / sneeze reflexe
• Respiratory tract anything 7 - 10 microns. Defences include - conducting airways - ciliary escalator (trapping in mucous for spitting of swallowing

Alveoli - 0.5 -7 microns. Defending mechanisms - alveolar macrophages (specialised attacking cells which ingest foreign particles)phagocytes attack and eat them

If particles can not be moved then inflammation of the membrane may occur which could result in scarring

Question 1

Explain the following terms

• LD 50
• LC 50

Answer 1

LD 50 = dose at which 50% of the test subjects die. (Administred orally or dermally) given in mg of substance per kg of body weight

LC 50 = is the concentration of air of airborne substance at which 50% of the test subjects die. Specified in mg per lt of air and a typical over a specified period of time usually 4 hours

Question 2

Outline the merits and limitations of using animals to study chemical reactions

Answer 2

Pros - well used / accurate / quick - alternative = epidemiological data relies on human exposure over a period of time / more closely biologically related to humans - vitro testing / avoids human harm

Cons - applicability / animal testing is completed in controlled labs rather than a work place - exposure patterns may vary / effects of combining chemicals (synergistic effects) will not be seen a laboratory / time consuming & expensive / controversial issue / difficulty in determining level at which no effects observed for carcinogens

Question 3

Compare and contrast the following epidemiological methods

• retrospective cohert study
• prospective cohert study

Answer 3

• Retrospective study = is looking backwards from now / use historical data
• Prospective study = is looking forwards from now / starting now and following the cohorts in time / exposure and health is monitored / involves selecting groups of exposed and unexposed individuals who are similar

Question 4

What is a cohert study

Answer 4

Concerned with establishing a cause effect or exposure - disease relationship. They use exposed and unexposed groups

Question 5

Outline factors that effect the reliability of cohert studies

Answer 5

Statistician significance / other influences / identifying historic exposures / drop outs

Question 6

Describe the main structure of the skin

Answer 6

the skin has a layered structure

• epidermis layer - outermost layer
  
  • horney zone (layers of dead cells that protect the outer
    surface & continually shed & replaced)
    -germinal or living zone (cells that reproduce the horney
    zone)
• dermis layer - is much thicker and contains
  
  • blood vessels (supply oxygen and cool skin)
  • sweat glands (excrete sweat to the surface of the epidermis)
  • nerve endings (pain, heat & pressure receptors)
  • hair follicles (thermal insulation)
  • sebaceous glands (secrete sebum onto skin for water
    proofing)

Question 7

Describe how hazardous substances can enter the body through the skin

Answer 7

Absorption - Skin is semi permeable once through-the skin chemicals can enter blood vessels. Especially if the glandular secretions are removed or their is damage to the skin

Cuts and grazes allow direct entry

Physical injection

Question 8

How does contact (primary) dermatitis occur

Answer 8

Contact with primary cutaneous irritants (chemicals & physical agents, frequent contact with water) these irritants degrease the skin and sensitisation occurs.

May not develop immediately or might arise from frequent exposure

Question 9

What are the causative agents, symptoms and mechanisms of damage of occupational pneumoconiosis

Answer 9

Non collagenous = caused by metal oxide (tin dust) has minor symptoms and is detected by observation of reversible structural changes of lung which can be seen in x rays

Collagenous = more serious condition caused by repair able asbestos,coal dust & cotton dust. Symptoms include cough, breathlessness & emphysema. The dust causes chronic inflammatory response which results in scar tissue in the lungs and loss of function. This can result from death from excess pressure on the heart

Question 10

Explain the information that may be needed to diagnose a case of pneumoconiosis

Answer 10

Work history / medical records / chest x ray / lung function / clinical examination

Question 11

Identify the ill effects of exposure to isocyanates

Answer 11

these are organic solvents found in paint spraying and foam manufacturing

irritants and allergen’s (inflammation of mucous membrane of nose and throat) symptoms and signs clear rapidly if user is removed

sensitization - violent recurrent symptoms - chronic asthma

very low exposure limit

Question 12

describe the routes of attack and entry methods that chemical substances can enter the human body

Answer 12

absorption or direct entry through breaks in the skin

1. inhalation - into the lungs - any inhaled substance which is capable of dissolving in water or passing through the membranes can enter the blood stream
2. skin contact - water soluble chemicals can not permeate through the skin. however some chemicals can pass through the epidermis layer (organic solvents benzene & toluene) they dissolve lipid membranes of the cells of the epidermis layer. chemicals can also enter via injection
3. ingestion - cross contamination of food. substance must be water soluble or able to pass through membranes to be absorbed. must reach part of the gastrointestinal tract where absorption can occur (small intestine)
4. aspiration - direct entry of liquid or solid into the lungs - sucked directly during pipetting or siphoning. or vomit which has run down the respiratory tract
5. mucus membrane of eye - be absorbed into the bloods stream
6. ear - through the ear cannel - organic solvents

Question 13

what are the body’s defence mechanisms to the attack of chemical substances

Answer 13

1. respiratory defences - nasal hair / mucus / sneeze reflex / cilary escalator
2. skin - epidermis layers of protection / water proof
3. ingestion - vomiting diarrhoea
4. eyes - tear ducts / eye lashes
5. ear - ear wax
6. blood - phagocytosis

inflammatory response

Question 14

describe phagocytosis

Answer 14

macrophages (form of white blood cell) destroy foreign particles ingesting them and secreting enzymes onto it then absorbs the digested remains

Question 15

what is inflammation

Answer 15

the means by which white blood cells are called to a site of infection or injury

if called upon for to long can cause disease - over production of scar tissue = emphysema

Question 16

what are the ill health effects of lead

Answer 16

inorganic lead

lead oxide in lead/acid batteries /chromate and red pigment. inhalation of dusts most serious - symptoms = nausea / vomiting & headaches / constipation / colic. brain affected = dullness / restlessness / tremor / coma. chronic symptoms - blue line on gums

organic lead

petrol anti knock agent & lead tetraethyl - inhalation & skin contact - symptoms = fatal - central nervous system / restlessness / raised level of excitement / talkativeness /muscular twitching and possible delusions and mania / fall in body temp and blood pressure

Question 17

what is human epidemiology

Answer 17

the study of patterns of ill health in populations

concerned with the distribution of a particular disease and the search to identify various factors involved

Question 18

what is in vitro mutagenicity (AMES) testing

Answer 18

toxicology tests completed in a test tube

AMES tests for mutagens by using a a non histidine containing bacteria. (histidine is an amino acid bacteria needs to grow) if the bacteria can go grow in the histidine free environment then it has become a mutagen when mixing with the desired chemical

Question 19

outline the diseases caused by asbestos including their ill health effects

Answer 19

1. asbestosis - collagenous pneumoconiosis - when fibres are inhaled into the alveoli and migrate into the surrounding tissues. resulting in inelastic scar tissue and thickening of the pleural membrane.
2. cancer of the lung & bronchus - combined effect of smoking tabacco and exposure to asbestos - spitting up blood
3. mesothelioma - cancer in mesothelium (the lining covering major organs) lungs and abdominal lining. asbestos fibres can migrate through lung tissues having a toxic effect on surrounding tissues

symptoms = breathlessness / coughing / pain between the shoulder blades and breast bone - reduced lung function resulting in pressure on the heart then death

Question 20

what information should be included in a chemical safety data sheet

Answer 20

• chemical product & company identification
• composition information on ingredients
• hazards identification
• first aid measures
• fire fighting measures
• accidental release measures
• handling & storage
• exposure controls & personal protection
• physical & chemical properties
• toxicological information
• ecological information
• disposal considerations
• transport information
• regulatory information

Question 21

Outline what is meant by respirable dust

Answer 21

Dust that is under 7 microns in aerodynamic diameter. This penetrates the gas exchange region of the lung

Question 22

Give the meaning of a carcinogen and an example

Answer 22

• An agent which has the ability to produce malignant tumours which may attack the cell reproduction mechanism
• causes changes in the cells DNA (production of abnormal cells with uncontrollable growth)
• effects are irreversible

Asbestos / wood dust / chromium used in alloys / vinyl chloride monomer

Question 23

Give the meaning of the term mutagen and give an example of where they might be found

Answer 23

Causes mutagens or changes in the DNA of cells and the damage caused can be passes on to future generations. The damage of the cell may kill it or lead to cancer

Acclaimed - formed naturally in starch rich foods are fried toasted or grilled

Question 24

Outline the meaning of the toxicity test - fixed dose

Answer 24

• used to determine acute oral toxicity
• used on animals usually rats
• starts with initial study to determine starting dose
• a single animal has a successfully Increased dose to determine toxicity effects
• test dose is chooses on one that can effect toxicity without mortality
• main study - animal tested on with 1 of 4 fixed doses 5, 50, 300 or 2000 mg/kg and observation carried out over 14 days
• the dose is determined and used as the basis for classifications such as very toxic, toxic and harmful or the equivalent GHS classification
• ## considered more humane the LD50 as it looks morbility rather than mortality & less animals are exposed

Question 27

Explain the meaning of the term toxicity

Answer 27

Is the degree in which a substance is able to cause damage to an organism

It can be chronic or acute - systemic or local effects

And divided into categories such as Carcinogens