B2 Identification, Assessment and Evalutation Of Hazardous Substances Flashcards
Basic description of the Respiratory system
Air enters the nose and passes through the nasal cavity, there it is warmed and moistened by water from the mucus membranes.
It passes out of the nasal cavity, through the pharynx (back of the throat) and then down the trachea (wind pipe)
The trachea carries air down into the thoracic cavity (chest) and divides into the two bronchi, the bronchus branches into bronchioles which branch into progressively smaller and smaller tubes.
These tubes lead to the aveoli (small looking grapes) where the moist oxygen meets the blood, this is the gas exchange where the inhaled oxygen passes into the bloodstream and carbon dioxide leaves the bloodstream and is exhaled.
Routes of entry
Inhalation
Ingestion
Skin contact/ injection/ absorption
Eyes
Others
Ear
Aspiration
Body defences (innate, non specific)
Skin - physical barrier Tears - Dilution Blinking Coughing Hairs in nose Mucocilary escilator Stomach acid Phagocytes Detoxification in the liver
Senses
Touch Smell Sound/ noise Taste Heat
Types of effect
Acute = single exposure, sudden on set short term.
Chronic = repeated exposure, delayed onset long term.
Systematic = Widespread throughout body eg bloodstream.
Localised = point of contact with substance ie burn.
Legislation controlling the use of chemicals in the work place.
Coshh Regulations
Control of lead at work Regulations
Control of asbestos regulations
Target organs and systems
Kidney (Urinary) = cadmium, carbon tetrachloride Bladder = napthylamine Skin = cement, latex, nickel Blood = arsenic, benzine Lungs = Asbestos, coal dust, isocynates Liver = chloroform, trichloroethane Nervous system = mercury, Reproductive
Four stages of the digestive system
INGESTION = through mouth with mastication (chewing) and swallowing.
DIGESTION = the breakdown of foodstuffs by enzymes secreted into it by the mouth, stomach and duodenum (first part of the intestine).
ABSORPTION = of breakdown products of digestion in the small and large intestine.
EXCRETION = of undigested food and waste through the rectum and anus.
Parts of the gastrointestinal tract
Mouth - Chews food, mixing food stuffs with saliva containing enzymes, start of digestion.
Oesophagus - swallowed food is squeezed by muscular contractions down this tube.
Stomach - acidic gastric juices are secreted from the stomach wall into the food. Digestion is full swing, food remains in stomach for some time.
Small intestine - Food from the stomach passes through the first part of the small intestine, the duodenum where further enzymes and bile are added, further digestion takes place.
- the food passes to another part of the small intestine, the ileum where the breakdown products of digestion (sugars, amino acids and fatty acids) are absorbed into the bloodstream.
Large intestine - water is absorbed from the remaining material which is then collected in the rectum prior to excretion.
Large intestine -
Circulatory system
Suppliers oxygen and removal of waste
Consists of heart, valves, blood vessels and blood.
Blood
Blood is 45% blood cells and 55% plasma
Plasma = straw coloured and high in salts
Blood cells
Erythrocytes (red cells) = these contain haemoglobin which allows the oxygen to be transported around the body.
Leukocytes (white cells) = there are three main types
- Granulocytes - these ingest harmful micro organisms such as bacteria by a process known as phagocytosis.
- Lymphocytes - production of antibodies which neutralise the effect of recognised foreign matter.
- Monocytes - change into macrophages and have a similar ingesting role as granulocytes.
- Thrombocytes (platelets) - main function is to clot the blood
Make up of the skin
EPIDERMIS = outer layer of skin made up of the horny layer, dead cells constantly being shed and the Germinal zone which is the living cells that reproduce to form the horny zone
DERMIS = thick layer of tissue which contains
- blood vessels = supply oxygen and help loose heat to the skin
- sweat glands = excrete sweat to help loose heat
- nerve endings = sensory stimulation and pain receptors
- hair follicles =
- sebaceous gland = oil glands to help suppress bacteria
Skin is impervious to water but can be permeated by other liquids such as organic solvents.
Nervous system
Brain and spinal cord
Respiratory system defences
Initial filtration of particles larger than 10 microns takes place in nasal cavity. INHALE ABLE
Smaller particles and aerosols between 7 to 10 microns are trapped in mucus lining the conducting airways and bronchi, bronchioles and transport up by the mucociliary escalator to the pharynx where it can be swallowed or expectorated (spat out). INHALEABLE
Smaller particles between 0.5 and 7 microns can pass into the Gas exchange region of the bronchioles and alveoli, here they may be ingested as foreign bodies by macrophages. RESPIRABLE
Below 5 microns remain airborne and are exhaled.
Two defence types
Innate (non specific) immune response
This is the response we are born with, it provides a rapid response but is non specific.
- Inflammation
- specialised white blood cells such as macrophages
Adaptive (acquired) immune response
This is targeted at a specific invader and takes time to develop
- specialist blood cells
Physical forms of substances
Solids
- Massive form ie lead ingot
- Dust
- Fibres
- Fumes
Liquids
- Fluid
- Mist
Gases
-Vapour
CLP labels must contain
Name, address and telephone number of supplier
Product identifiers such as product name, CAS Number
Hazard pictograms and signal words such ass danger
Hazard statements and applicable precautionary statements
Supplemental information
Safety data sheets
REACH requires suppliers to provide safety data sheets containing information under 16 headings
- Supplier details
- Components and overall hazards
- What to do if things go wrong (first aid, fire fighting and accidental release)
- How to stop things going wrong
- Basic properties ie physical, chemical and toxicological.
- Disposal and transportation.
- label and regulatory information
- Anything else
Steps of a coshh Assessment
Information about the substance Evaluate the risk to health Decide on control measures Record assessment Review and update as necessary
Factors to consider when assessing health risk
COSHH Assessment Hazardous properties of the substance Type and level of exposure Duration and frequency of exposure Number of people Effect of mixtures Unusual activities WELS Existing controls Health surveillance/ monitoring Individual suseptabilites Review
Toxicology and epidemiology
Toxicology = the study of adverse effects of chemicals on living organisms
Epidemiology = study of patterns of ill health in populations (identify link between exposure and illness)
Hierarchy of controls for carcinogens
- Eliminate
- Substitution
- Engineer out
- Control at source
- Use organisational measures to control numbers exposed, level, duration
- Control the working environment
- Prohibition of eating/ drinking/ smoking in potentially contaminated areas
- Clean surfaces
- Design potentially contaminated areas and use warnings
- Use safe storage, handling and disposal methods
- PPE as last resort
- Health surveillance for exposed workers
- Develop Emergency spillage procedures
Case control study
Retrospective study, beginning with a definition of a group of cases (people with the disease known as the case) and comparing these to a group without the disease (the control).
Looking at past exposure history to try to draw a conclusion
Drawback = hard to gain an accurate exposure history of the two groups and may need to go as far back as 40 years.
Prospective cohort study
This is a case controlled study following two groups forward in time.
Comparing those exposed and those who are not, to determine possible links between exposure (cause) and possible incidents (effect)
Drawback = can take a long time, there can be a loss of the study groups death by other causes etc. Can be expensive
Retrospective cohort study
Similar to the prospective cohort only this starts with the disease and no diseased cohorts and then looks back at the exposure history.
Animal testing (toxicity tests)
Acute toxicity = single exposure, testing for short term effects Skin sensitisation = testing for potential contact dermatitis Repeat does (28 day) toxicity = multiple exposures, testing for medium term effects. Sub chronic repeat dose (90 days) toxicity = multiple exposure, longer term onset. Chronic toxicity = long term effects following life time multiple exposures. Mutagenicity = testing to determine if substance has the ability to cause genetic damage Carcinogenicity = if mutagenic tests prove positive the animal is exposed to a lifetime exposure of the substance and post-mortem carried out to detect tumours Reproductive toxicity = examine effects of substance or embryo or foetus to identify abnormalities
Advantages of animal testing
- Can be quicker and cheaper than epidemiology studies
- Doesn’t rely on exposing people to chemicals and substances so preventing human pain and suffering
- Gives good quality of information about effects of exposure that can not be determined by other studies.
- Allows long term effects of exposure to low doses to be studied, replicating what workers may experience
Limitations of animal testing
- Responses vary between species, so may not represent effects on a human
- Testing on animals raises ethical questions
- Not representative of human life styles which could have effect of diseases such as cancers.
- May take a long time and be expensive
Alternatives to animal testing
In-vitro studies = test tube or Petri dish, test uses bacteria etc. Ames test for mutagens using a defective histidine gene.
Predictive studies - grouping and read across, looking at related chemicals and their effects. This data would still require further vitro or in vitro testing to prove data but would reduce the need for animal testing.
Quantitative , structure - activity relationship QSAR uses a computer modelling to predict how substances will act/ effect the human body. Will still require further testing to prove data.
