IB-1 Principles of Chemical Control Toxicology & Epidemiology Flashcards
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
- 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
Explain the following terms
- LD 50
- LC 50
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
Outline the merits and limitations of using animals to study chemical reactions
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
Compare and contrast the following epidemiological methods
- retrospective cohert study
- prospective cohert study
- 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
What is a cohert study
Concerned with establishing a cause effect or exposure - disease relationship. They use exposed and unexposed groups
Outline factors that effect the reliability of cohert studies
Statistician significance / other influences / identifying historic exposures / drop outs
Describe the main structure of the skin
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)
- horney zone (layers of dead cells that protect the outer
- 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)
Describe how hazardous substances can enter the body through the skin
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
How does contact (primary) dermatitis occur
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
What are the causative agents, symptoms and mechanisms of damage of occupational pneumoconiosis
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
Explain the information that may be needed to diagnose a case of pneumoconiosis
Work history / medical records / chest x ray / lung function / clinical examination
Identify the ill effects of exposure to isocyanates
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
describe the routes of attack and entry methods that chemical substances can enter the human body
absorption or direct entry through breaks in the skin
- inhalation - into the lungs - any inhaled substance which is capable of dissolving in water or passing through the membranes can enter the blood stream
- 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
- 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)
- 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
- mucus membrane of eye - be absorbed into the bloods stream
- ear - through the ear cannel - organic solvents
what are the body’s defence mechanisms to the attack of chemical substances
- respiratory defences - nasal hair / mucus / sneeze reflex / cilary escalator
- skin - epidermis layers of protection / water proof
- ingestion - vomiting diarrhoea
- eyes - tear ducts / eye lashes
- ear - ear wax
- blood - phagocytosis
inflammatory response
describe phagocytosis
macrophages (form of white blood cell) destroy foreign particles ingesting them and secreting enzymes onto it then absorbs the digested remains
what is inflammation
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
what are the ill health effects of lead
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
what is human epidemiology
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
what is in vitro mutagenicity (AMES) testing
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
outline the diseases caused by asbestos including their ill health effects
- 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.
- cancer of the lung & bronchus - combined effect of smoking tabacco and exposure to asbestos - spitting up blood
- 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
what information should be included in a chemical safety data sheet
- 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
Outline what is meant by respirable dust
Dust that is under 7 microns in aerodynamic diameter. This penetrates the gas exchange region of the lung
Give the meaning of a carcinogen and an example
- 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
Give the meaning of the term mutagen and give an example of where they might be found
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
Outline the meaning of the toxicity test - fixed dose
- 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
Explain the meaning of the term toxicity
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
