B4 Monitoring and Measuring Hazardous Substances Flashcards
WELS
Work place exposure limit set under COSHH in EH40
Lead and asbestos have their own limits set under CLAW and CAW regulations
Gas/ vapour= ppm
Dusts mg/m3
WELS set by the advisory committee on toxic substances and set the maximum time weighted average airborne concentration of a substance to which workers can be exposed to.
NOAEL
NOAEL = No Observable Adverse Effect Level
How are WELS established
WELS are set by the advisory committee on toxic substances (ACTS), following an assessment of toxicological, epidemiological and other relevant data.
WELS setting is done as a three stage process
1) Assessment of toxicology of substance to identify its does response and set its NOAEL, the point on the dose response curve below which no adverse response noted. Not all substances have a NOAEL such as a genotoxic carcinogen.
2) NOAEL is used as a starting point to determine the highest exposure level, an estimate is then made to work out the highest level of exposure that a worker maybe exposed to on a daily basis for the rest of their working life, without experiencing ill health effects (this data is based on animal studies so an estimate is built in with a safety factor)
3) Determine actual levels of exposure that are being achieved or are realistic in the workplace. If that level is below the identified level then the WEL is set.
Where substances do not have a set NOAEL or it is not reasonably Practicable to achieve control to the identified level then ACTS will set a WEL in line with good hygiene practices, where ever possible a WEL is not set at a level where there is positive evidence of adverse effects on human health.
Interpretation of occupational hygienist reports
Reports should include/ cover the following
- Appropriate strategy and method of sampling used
- The Equipment was maintained, certificated and calibrated
- Carried out at a time and place that would be representative of real working conditions
- Results have been evaluated against correct legal standards
- Actions required to remedy any failures
- dated
- state site, area, what the report converted, legal reference used to validate actions required
- Name, credentials of persons carrying out test.
HSG 173 monitoring strategies for toxic substances
Initial appraisal:
- Gather information such as information on substance (WELS, physical form, health effects), routes of entry, process where exposure likely to occur, numbers, groups likely to be exposed, existing control measures.
- Conduct qualitative test such as smoke tubes, dust lamps, smell,
Basic survey if the initial appraisal indicates exposure is unacceptable, this looks at the worst case scenario and requires
- Personal sampling of those most likely to be at risk
- Static sampling
- Risk Assessment to decide if Risk is acceptable or not
Detailed survey used when:
- Dealing with carcinogens, mutagens and respiratory sensitisers
- Exposure is highly variable between employees doing similar tasks
- the initial appraisal and basic survey indicate
- TWA concentrations are very close to WEL and additional control costs need to be justified with more detailed evidence.
Four stages in the practice of occupational hygiene
- Recognition/ identification of the hazards
- Measurement of the hazard/ extent of exposure (who and by how much)
- Evaluation against recognised standards - judgement on risk posed
- Control- putting measures in place to reduce or eliminate
Describe gravimetric method for measuring dust
Using a sampler connected to an air pump via a hose.
- Clean and load sampler with pre weighted filter or cassette
- Fit sampler to pump and run
- Connect sampler to operators (no more than 30cm from nose mouth region)
- Record start time of sampling, Check and adjust flow
- Record end time and remove filter for weighing
- Recheck flow rate
- Once filters weighed a simple calculation is carried out to give dust per cubic meter orphan air (mg.m3)
Sampling Asbestos
Air measured using a downward facing cowled sampler head
The amount of asbestos collected is quantified by counting fibres by phase contrast microscopy
Only fibres in excess of 5 microns and a width of less than 3 microns and a width to length ratio of 3:1 are defined as countable
Difference between health assessment and Health surveillance
A health assessment is an assessment to determine the state of someone’s health or fitness for general duties or specific tasks associated with work ie pre employment assessment! It is usually carried out by occ health doctor or nurse.
Health surveillance is a more specific assessment of a workers fitness that focuses on one specific aspect in relation to a particular hazard. The assessment assesses the workers health in regards to that hazard and then tracks that workers health going forward.
Legal requirement for health surveillance
MHSWR section 6 is a general duty to provide health surveillance
COSHH reg 11 specific duty
Control of noise at work
Control of vibration at work
Legal Requirement for medical surveillance
COSHH
CLW
CAW
Ionising radiation regulations
What is biological monitoring
Biological monitoring is the measurement and assessment of workplace agents exposed to workers and is the measurement of breath, urine or blood or any combination of these.
It can indicate how much chemical has entered a workers system
Advantages and disadvantages of biological monitoring
Advantages
- identify what has actually been absorbed by the body
- measurement of exposure by all routes of entry
- demonstrates if Controls are effective
- gives reassurance to workers their exposure is being monitored
Disadvantages
- costly
- requires a doctor or nurse to take blood
- data relates to an individual and data protection issues need to be addressed
-
Specific criteria that must be met before health surveillance becomes a legal requirement
The criteria set out by the MHSWR Regulation 6 are:
* There is an identifiable disease or adverse health condition related to the work concerned
- Valid techniques exist to detect indications of disease or condition
- There is reasonable likelihood that the disease or condition may occur under particular work conditions
- Surveillance is likely to further the protection of the health and safety of the employees
Difference between health record and medical record
HEALTH RECORD is a record of the conclusion of a clinician (such as OH doctor) on health surveillance results, it doesn’t contain clinical information and as such is not medically confidential.
MEDICAL RECORD is created by a clinician and contains clinical information and as such is medically confidential.
