EXPOSURE ACTION

The 5-HT receptors function as ligand-gated ion channels and are expressed in the area postrema and solitary tract nucleus, where they couple to potent depolarizing responses that show rapid desensitization to continued 5-HT exposure. Actions of 5-HT at central 5-HT receptors can lead to emesis and antinociceptive actions, and 5-HT antagonists are beneficial in the management of chemotherapy-induced emesis (see Chapter 37). 

Despite this theoretical position, in practice the trade unions r x)gmse that the process of establiriiing health-based Europe-wide recognised OELs is very time consuming. They therefore accept (in order to speed up the process for getting OELs at all) for the time being what they call technical OELs, or occupational exposure action levels . 

The exposure action value (EAV) is a daily amount of vibration exposure, above which employers are required to take action to control exposure. Daily exposure action value is 2.5 m/s. ... 

Lower limit of concentration associated with toxicity/occupational exposure action limit. 

Action level— The amount of a material in air at which certain OSHA regulations to protect employees take effect. Exposure at or above the action level is termed occupational exposure. Action plan—Documented outline of specific projected activities to be accomplished within a specified period, to meet a defined need. 

To avoid an unacceptably high exposure from radon, many countries have introduced limitations on the radon concentration in dwellings for chronic exposures. Action levels have been designated above which protective actions should be carried out to decrease chronic exposure. In most countries, action levels for dwellings are established between 200 and 600 Bq m for the annual average radon concentration, based on representative measurements and other parameters. 

Noise is measured in decibels (dB). The Regulations require the employer to take specific action at certain action values. The Regulations define exposure action values -levels of noise exposure which, if exceeded. 

The employer must provide health surveillance for all employees who are likely to be exposed above the upper exposure action values, or are at risk for any reason, e.g. they already suffer from hearing loss or are particularly sensitive to damage. 

The source of noise and vibration on demolition sites will normally be caused by the use of plant and equipment, falling debris and/or explosives. Compressors, pneumatic hand-held tools, front end loaders, excavators and other equipment can create noise levels of more than the lower exposure action level of 80dB(A) and may at times create peak noise levels of more than 137 dB(C) the lower peak sound pressure action value. A noise assessment will be required and workers given ear defenders. 

An exposure limit value must not be exceeded. If an exposure action value is exceeded, then action must be taken to reduce the value. The expression A(8) is added to the exposure limit or action value to denote that it is an average value spread over an 8-hour working day. Thus the daily exposure limit value for hand-arm vibration is 5 m/s A(8). 

The Control of Noise at Work Regulations specify exposure action levels at which the hearing of employees must be protected. The conclusion as to whether any of those levels have been breached is reached after an assessment of noise levels has been made. However, before noise assessment can be discussed, noise measurement and the statutory action levels must be described. 

The Regulations introduce exposure action level values and exposure limit values. 

An exposure action value is a level of noise at which certain action must be taken. 

Where there are things that can be done to reduce risks from noise that are reasonably practicable, they should be done. However, where noise exposures are below the lower exposure action values, risks are low and so employers would only be expected to take actions which are relatively inexpensive and simple to carry out. 

Where this is not reasonably practicable and the risk assessment indicates that an exposure action value is likely to be reached or exceeded, the employer shall reduce exposure as low as reasonably practicable by establishing and implementing a programme of organizational and technical measures which is appropriate. 

This shall not apply where the exposure of an employee to vibration Is usually below the exposure action value but varies markedly from time to time and may occasionally exceed the exposure limit value, provided that ... 

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