Asbestos control limits

EH 10 Asbestos — control limits and measurement of airborne dust concentrations (1984) EH 11 Arsine - health and safety precautions (1977)... 

Asbestos control limits are determined by fibre counting with the phase contrast opticai microscope, and are ... 

Acheson, E. D., and M. J. Gardner (1983). Asbestos The Control Limit for Asbestos. Health and Safety Commission, Her Majesty s Stationery Office, London. 

Control limits for asbestos dust in the working environment are ... 

A singie tighter control limit for all types of asbestos... 

If, despite the use of other control measures, exposures still have the potential to exceed the control limits, employers must provide suitable respiratory protective equipment and make sure that it is used correctly by those carrying out the work. Employers must choose RPE which is designed to provide an adequate margin of safety. To be suitable, RPE must be matched to the job, the environment, the anticipated maximum exposure, and the wearer. It should be checked to make sure it is compatible with the personal protective equipment (PPE), particularly that any PPE which protects the head or eyes of employees does not affect the fit of the RPE. It must reduce the concentration of asbestos fibres inhaled to a concentration which is as low as is reasonably practicable, and in any case to a level which is below the control limits. 

Designated asbestos areas should be marked out to prevent or reduce exposure and the spread of contamination, by making sure that workers do not enter areas where they may be unknowingly exposed to significant concentrations of asbestos (i.e. such that the action level would be exceeded if the workers spent their normal work time exposed to that concentration of asbestos). Where potential exposure is such that control limits are liable to be exceeded, respirator zones should be marked out to ensure that RPE is worn. 

Monitoring of employee exposure should be carried out as appropriate to protect the health of employees by determining or checking the concentrations of airborne asbestos to which they are exposed. This should consist of personal sampling followed by analysis using a method approved by the Health and Safety Commission. Information on employee exposure needs to be compared with the action levels and the control limits, as the results may trigger the need for certain control measures. 

Monitoring should always be done when there are any doubts about the effectiveness of the measures taken to reduce the concentration of asbestos in air, and, in particular, measures taken to reduce that concentration below the relevant control limit. 

If the control limit for asbestos is exceeded in the working area, this triggers particular requirements including ... 

Air monitoring should always be done when there are any doubts about the effectiveness of the measures taken to reduce the concentration of asbestos in air (e.g. that engineering controls are working as they should to their design specification and do not need repair), and, in particular, measures taken to reduce that concentration below the control limit or below a peak level measured over 10 minutes of 0.6f/m . Monitoring will also be necessary to confirm that the RPE chosen will provide the appropriate degree of protection where the level of asbestos fibres in air exceeds, or is liable to exceed, the control limit or a peak level measured over 10 minutes of 0.6f/m . 

Control limits are based on Regulations, Approved Codes of Practice, European Community directives, or Health and Safety Commission instructions, and are limits which should not be exceeded. Failure to comply with a control limit may result in enforcement action by a Health and Safety Executive Inspector. With some controlled substances (i.e. those with no minimum threshold below which adverse effects do not occur, or where short exposure to high concentrations cause injury) exposures may need to be reduced to the lowest levels justifiable on a cost/risk basis. The present strategy behind the application of control limits for exposure to relatively few substances, some of which are not highly toxic, is based on the recognition that these substances are very commonly used at work. Until a few years ago, a great many were used without any real control of exposure (e.g. asbestos, vinyl chloride and lead compounds). Some, such as methylene chloride, formaldehyde and styrene, have been shown more recently to be potentially very harmful, in both the short and the long term, at levels of exposure just above the limits set, and they are included because of their widespread use at work. 

Workplace exposure is usually assessed by personal sampling in which a known volume of air is sucked through a membrane filter which is subsequently prepared for examination by phase-contrast optical microscopy, and respirable fibres counted using predetermined rules (HSE, 1990). 0.5 0.2 f/ml control limits for chrysotile and amphibole asbestos exposure respectively has been introduced in the UK, and a 2f/ml maximum exposure to MMMF has been agreed, running in parallel with a 5mg/m gravimetric limit. 

Amosite - brownish in colour unless subjected to high temperature, this form of asbestos is now considered as dangerous as crocidolite. In 1984 it was made subject to the same control limits. 

The reason for the chosen work method Details of expected exposures, including whether they are likely to exceed the action level or control limit (see below) and the number of people affected Steps to be taken to reduce exposure to the lowest level reasonably practicable Steps to be taken to reduce release of asbestos into the environment and for the removal of waste Procedures for provision and use of personal protective equipment... 

A control limit is that concentration of asbestos in the air, averaged over any continuous 4-hour or 10-minute period, to which employees must not be exposed unless they are wearing suitable respiratory protective equipment (RPE). Control limits are expressed in fibres per millilitre of air averaged over the period. 

Control limits and action levels for asbestos are given in Table 15.1. If the assumption is made that the material is not chrysotile alone, then the more stringent limits and level must be used and there will not be a need to identify the type of asbestos. 

The intention of marking asbestos areas (Regulation 17) is to make sure workers do not enter them unknowingly. A work area can be designated as an asbestos area (because the workers may exceed the action level) or a respirator zone (because either of the control limits may be exceeded), or both. 

Asbestos type 4-hour control limit (fibres/ml) 10-minute control limit (fibres/ml) Action level (fibre-hours/ml)... 

The 2003 ACGIH threshold limit valuetime-weighted average (TLV-TWA) for particulate matter containing no asbestos and <1% crystalline silica is 3mg/m for respirable size fraction and lOmg/m for inhalable mass fraction. Exposure to any substance in the particulate mass that has a designated TLV should be controlled to that value. 

Toxic Substances Control Act (TSCA) Law passed in 1976 that governs the regulation of toxic substances in commerce, with the objective of preventing human health and environmental problems before they occur. The manufacturing, processing, or distribution in commerce of toxic substances may be limited or banned if EPA finds, based on results of toxicity testing and exposure assessments, that there is an unreasonable risk of injury to human health or the environment. Important hazardous chemicals regulated under TSCA include, for example, dioxins, PCBs, and asbestos. 

The CIPE plan called for a remediation of asbestos-containing materials in the Etemit and in the ILVA steelwork factories. Ninety percent of the buildings, squares, and sites were cleared of asbestos by March 4,2000. During the remediation activities, and in coordination with the local Health Unities (ASL)), a series of control samples were collected. 915 samples were analyzed to evaluate the presence of aerially dispersed asbestos fibers in nearby locations. No values exceeding WHO limits were detected. 1044 samples and analyses from the Etemit site and 56 from the ILVA site were also collected to monitor fiber dispersion inside the area of the operations. 

In a previous section, data and plots were given showing the rapid rise in consumption and production of manufactured fibers at the expense of natural fibers. The principal reason for this has been the wide range of manufactured fiber variants that can be produced from a single fiber-forming polymer. The wide range of polymers available, each with its particular properties, adds yet another dimension. This is not to say that there is only one type of cotton, wool, silk, or asbestos fiber there are many varieties of natural fibers, but their supply is limited by natural factors such as climate and genetics. The relative availabilities of manufactured fiber types can be altered by controlled chemical-process... 

American Conference of Governmental Industrial Hygienists threshold limit value (TLV) lOmgm for total zinc oxide dust (containing no asbestos and <1% crystalline silica), as a TWA for a normal 8h workday and a 40h workweek TLV — TWA of 5mgm and a TLV — STEL (short-term exposure limit) of lOmgm for zinc oxide fume (based on providing reasonable control of this nuisance dust). 

The difference betw n the two types of French limit values, their enforcement, and the possibilities labour inspectors have become clear when loddr at the power of the Labour Inspectorate with respect to these two OELs. Air quality control measurements by the labour inspectors are only possible tor substances for which a binding limit value exists, which are thc e tor dust/fibres of asbestos, lead, benzene, vinyl chloride monomem etc. For substances for which indicative limit values have been adopted and published, the ender of 9 October 1987 does not allow the labour inspectors to enforce these OELs directly by issuing inqjrovement or entorcement orders. The nature of these limit values ( indicative/guidance ) does not pennit prescription of exact measures to enforce them. The cmly possibility to enforce them is via indirect sanctions on failures of the ventilation system and similar offences. 

The effect of this new policy will be the development, whenever possible, of quantitative RELs that are based on human and/or animal data, as well as on the consideration of technological feasibility for controlling workplace exposures to the REL. Under the old policy, RELs for most carcinogens were non-quantitative values labeled lowest feasible concentration (LFC). [Note There are a few exceptions to LFC RELs for carcinogens (e.g., RELs for asbestos, formaldehyde, benzene, and ethylene oxide are quantitative values based primarily on analjdical limits of detection or technological feasibility). Also, in 1989, NIOSH adopted several quantitative RELs for carcinogens from OSHA s permissible exposure limit (PEL) update.]... 

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