B4 Ollie Flashcards
Workplace Exposure Limits (1)
Airborne concentrations , averaged overtime, which according to current knowledge are thought to be safe
Published every year in HSE
Environmental lHealth EH40
Substances are allocated a WEL in either parts per million (ppm) or milligrams per cubic metre (mg/m3)
Basis for determining compliance with COSHH Regulations
Workplace Exposure Limits (2)
WELs MUST not be exceeded
Principles require that reduction below WEL to be proportionate to the health risk
Some WELs must be must be reduced to a level as low as reasonably practicable :
Carcinogens and mutagens (R45, R46, R49)
Respiratory sensitisers (R42, R43)
Lack of WEL does not mean substance is safe
Workplace Exposure Limits - WATCH & ACTS
WATCH:
Working Group on Action to Control Chemicals
Reviews scientific evidence and publishes risk assessments
Scientific evidence includes epidemiological studies /animal testing etc
ACTS:
Advisory Committee on Toxic Substances
Considers evidence and takes into account socio-economic factors Makes recommendation to HSE
Workplace Exposure Limits - First & Second Level
First: Set at a level where there is no adverse affects on human health(NOAEL) - exceptions : Genotoxic carcinogens Asthmagens Mixtures Lackof data If not reasonably practicable
Second:
Set at a level that is considered to represent good control
Workplace Expos ure Limits - 8Hour TWA
Represent an average level of exposure measured over an eight hour working shift
Calculated by:
8 hour TWA=C1T1+ C2T2+ C3T3……divided by 8 hour period
C = Concentration
T = Time (hours )
Role of the Occupational Hygienist
Usually trained to Degree level, and preferably a member of British Occupational Hygiene Society (BOHS)
Identification of occupational health hazards
The measurement and evaluation of exposure to hazards Interpretation of results
The design of control measures
Education and training of workers and management
Preparation of labels and keeping of records Conducting research
Why Measure Airborne Contaminants ?
Risk assessment To ensure compliance with WELs To determine design of control measures To check effectiveness of controls To indicate the need for health surveillance To establish in-house standards Insurance Legal requirement
Legal Requirements
COSHHReg 10:
If risk assessment indicates that it is requisite for ensuring maintenance of adequate control
COSHH Schedule 5:
VCM continuous , chromium electrolysis every 14 days
CAR:
If likely to exceed control limit (0.1f/cm3 of average air over 4hr period)
CLAW:
Every 3 months if exposure likely to be significant (lead other than lead alkyls 0.15mg/m3 & lead alkyls 0.10mg/m3)
Types of Monitoring
Static sampling
Personal monitoring
Monitoring Strategy (HSG173)
Initial Appraisal:
If exposure not under control - move to
Basic Survey:
Evaluate results - if more information is required or conclusion not certain - move to
Detailed Survey:
Following conclusions - carry out reappraisal & monitoring
Initial Appraisal
Enables you to decide on risks and hazards
Enables you to decide if monitoring is required
Consider:
Substance, physical properties , points of exposure, number and nature of release points , pattern and degree of exposure, WELs
Sources of information:
Labels , safety data sheets , HSE publications , technical literature, experience etc
Simple qualitative tests:
Smoke tubes , dust lamp (MDHS 82), odour
Methods for the Determination of Hazardous Substances
Series of publications from HSE
Provide standard methods for analysis
Currently 125 methods
Can be downloaded from HSE website
Examples:
MDHS14/3: General methods for sampling and gravimetric analysis of respirable and inhalable dust
MDHS 82: The dust lamp, a simple tool for observing the presence of airborne particles
Basic Survey (1)
Estimates exposure, estimates efficiency of engineering controls
Needed if:
There is an exposure risk and level uncertain Major changes made since last assessment
Unusual operations planned (e.g. maintenance)
New process/WEL
Basic Survey (2)
Estimates personal exposure, estimates efficiency of engineering controls
Uses semi-quantitative methods: Indicator (Draeger)tubes Computer exposure monitoring Photoionisation Detectors Flame Ionisation Detectors Portable Gas Chromatographs Infra-red Analysers
Detailed Survey
If the extent cannot be determined by the basic survey
Exposure highly variable between employees Carcinogens or senstisers involved
If BS indicates close to WEL and cost not justified Complex and usually involves occupational hygienists Quantitative methods e.g. personal samplers
May need to include biological monitoring
Factors Affecting Airborne Contaminant Exposure
Physical and chemical properties
Number of sources
Rate, duration and release from each source
Arrangement of the process , temperature and design of control measures
Dispersion or mixing due to air movements /gdv Proximity/frequency of employee exposure to source If employee has control/poor appreciation
Factors Affecting the Design of Monitoring Strategies
Health effect e.g. chronic or acute Grouping of employees: Similarly ExposedGroups (SEGs) Type of measurement: Personal or static, representative or worst-case Duration: Depends on variables in exposure e.g. 25% of shift Sampling equipment: Heavy, battery life etc Accreditation/ quality control : NAMAS, WASP, MDHS
Reappraisal/Routine monitoring
Reappraisal: Change in process Change in number of personnel Routine monitoring: To ensure controls remain effective Specific requirement e.g. VCM continuous (COSHH Schedule 5) COSHH Regulation 10
