Occupational exposure limit types

An indicative limit value is a more common type of limit that reflects expert evaluation based on scientific data where it is possible to identify the highest level of exposure along with the corresponding reference time period for which one can have confidence that there will be no adverse effects on health. For any chemical agent for which an indicative occupational exposure limit value is established at the community level, member states shall establish a national occupational exposure limit value, taking into account the community limit value and determining its nature in accordance with national legislation and practice. 

Occupational exposure limits for airborne contaminants are reviewed annually in the UK by the Health and Safety Executive. They are published as Guidance Note EH 40/ —. The two types of exposure limit are ... 

Several other types of occupational exposure limits are derived in addition to the OELs derived to protect against airborne chemical exposures in traditional workplace settings. 

Although epidemiological data provide the strongest evidence that specific chemicals affect human health, occupational exposure limits and other preventive measures typically are not based on these types of data alone. The number of chemicals to which workers are exposed far exceeds the number of solid epidemiological studies. Therefore, many occupational health standards and protective health measures are based on data from toxicology studies. Consequently, one of the major challenges that faces an occupational toxicologist is how to interpret the results obtained from animal studies and molecular studies for application to humans. 

Types of Occupational Exposure Limits until 31 December 2004. Until 31 December 2004, three limit values were in use in Germany ... 

Aside from the definitions presented above, section I of directive 98/24/EC contains basic principles on the procedure for establishing of occupational exposure limits on the European Community level. The following types of limits have to be distinguished ... 

The term binding occupational exposure limit value (BOELV) was introduced in article 3,4 of the chemical agents directive 98/24/EC. This type of Hmit is established in accordance to J 118 a of the European Treaty and is Hsted in the annex of this directive. According to the procedure for incorporation of limit values into national laws, the EU member states are required to adopt a national occupational exposure limit, which may be equal to or below the Hmit, but not higher than the BOELV. The procedure for establishing BOELV is quite complicated. Besides the toxicological properties, feasibility plays an important role. This includes technical aspects as well as considerations of the excess risk at estimated exposure levels. The acceptable-risk approach for genotoxic substances requires intense discussions on socio-economic factors between aU interested parties. 

In cases where respiratory devices are used to avoid exceeding occupational exposure limits, chemical protective suits are necessary. These are available for use against many different chemicals, and are made from various types of elastomer materials or coated fabrics. Most chemical protective suits enclose the whole body. In order to reduce any leaks, the protective boots are integrated. Normally one can choose from protective suits having fiiU face masks with a connector for a cartridge or an external compressed air breathing apparatus (Fig. 6.25 b), or with an... 

A.2.8 Exposure controls personal protection. Engineering measures recommended to control exposure should be covered, together with any occupational exposure limits or biological standards. Where personal protection is needed, the type of equipment should be specified. This will cover ... 

In the United Kingdom, there are two types of occupational exposure limits occupational exposure standards (OESs) and maximum exposure limits (MELs). An OES is set at a level at which there is no indication of risk to health, while the MELs are set for materials for which serious health implications exist, but which due to socioeconomic factors must have a numerically higher value in order for the controls associated with certain uses to be regarded as reasonably practicable. 

There are two types of occupational exposure limit which have different criteria ... 

In the past, the HSE has incorporated the American TLV system in a Guidance Note which was published annually. This practice continued until 1984 when a UK system of limits was adopted. Since that time, there have been several types of UK occupational air quality standards including the two-tier Control and Recommended Limit and, until recently, the Maximum Exposure Limit and Occupational Exposure Limit. Both these two-tiered systems defined exposure standards with different requirements for legal compliance. These systems have now been abolished and replaced by the current single-tier Workplace Exposure Limit (WEL) system. The WeL system now forms part of the requirements for adequate control of exposure by inhalation under the COSHH Regulations 2002 (as amended) . 

The occupational exposure limits for the UK are published in EH40. Since April 2005, when the fifth edition of COSHH Regulations 2002 (as amended) was issued, the previous system of setting occupational exposure limits (OELs) as maximum exposure limits (MELs) and occupational exposure standards (OESs) has been discontinued. They have been replaced by a single type of OEL known as the workplace exposure limit (WEL) which has legal status under regulation 7(7)(b) of COSHH. Incorporated in the data on exposure limits contained in the HSE s publication EH40 are the Indicative Occupational Exposure Limit Values (lOELVs) adopted by the EU. 

At the present time, the exposure of people at work to chemical hazards is controlled by reference to the limits set by safety authorities, i.e. the occupational exposure limits set by the Health and Safety Executive in the UK and threshold limit values set by the Occupational Safety and Health Association in the USA. In the UK two types of limits are currently in operation recommended limits and control limits. 

Once a scheme is set up and operational, whoever manages the job for which personal protection is required should have established procedures for updating that protection to cope with changes to the process itself or to the materials used in it, reductions in the occupational exposure limit, any change of personnel, the availability of new systems of protection or the lack of availability of current types of protection. Written procedures concerning the scheme should be made available. 

Calculation of the occupational exposure concentration (OEC) depends on the type of OEL. For example, when the limit value has been set as an eight-hour time-weighted average, the cumulative exposure for an eight-hour work shift should be computed as follows ... 

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