Lead in Air Standard

Increased use of leaded gasoline in Canada may generate pressures to control automotive exhaust lead emissions, although there is no established health-based lead-in-air standard to serve as the basis for such control. If reduction of automotive lead emissions into the atmosphere should be required, controls should be placed on the amount of lead emitted from the tailpipe, similar to the manner by which gaseous emissions are controlled. Such action is more energy efficient than reducing the amount of lead used in gasoline. One effective way to control tailpipe lead emissions is the use of automotive exhaust lead trap that replaces the standard muffler (2). 

The Approved Code of Practice suggests that exposure to lead is significant if the level of airborne lead is in excess of half the lead-in-air standard or there is a substantial risk of ingesting lead or there is a risk of skin contact with concentrated lead alkyls. For lead-in-air the standard for an 8 hour time weighting is an average concentration of 0.15 mg/m of air except for tetraethyl lead where the level is 0.10mg/m of air. 

The assessment procedure is vital, and it is something new to be brought into the sphere of Regulations. Assessment will be incorporated into the Control of Substances Hazardous to Health Regulations, which are proposed (from 1987/88) to cover all work-related aspects of the use of hazardous substances, and they will follow a very similar pattern to the Lead Regulations. The purpose of assessment in the Lead Regulations is to determine (a) compliance with the Lead in Air Standard (b) whether exposure to lead is significant (c) what action is required and (d) any risk to other people. Obviously, the more lead there is in the workplace, and the more complex the process, the more detailed the assessment will need to be. 

The Lead in Air Standard relates to personal exposure, and so it means wearing a personal sampler for the Lead in Air measurements (personal sampling equipment is... 

Environmental Standards. Lead in the environment is regulated in the United States because of its potential occupational impact, as well as concern about the impact lead may have on the cognitive and physical development of young children. Standards have been set for lead in air, water, and other environmental media. 

For those personnel working in low risk areas, the use of a paper comfort mask should be strongly discouraged. These masks do not provide a good seal around the mouth and nose and do not conform to the standards required for protection from lead-in-air. As a minimum standard, only those paper masks specifically designed for particulates and welding (with neoprene face seals and adjustable nose clips)... 

Where possible all processes in which dust or fume is generated are enclosed and vented to the outside. Where this is not possible the workplace atmosphere is forcibly extracted to provide ample ventilation and to keep lead-in-air to acceptable levels. In areas where industrial hygiene standards are liable to be exceeded, personal respirators are issued to workers to provide a constant supply of uncontaminated air for breathing. Deposited dusts are frequently removed. 

The impHcation of this wide range of blood leads within a population is important for standard setting based on PbB. For instance, the US Environmental Protection Agency (US EPA) has promulgated a standard for lead in air based on achieving a target of a population median PbB for children of <15 jug (100 ml)" [19]. They are thus implicitly accepting that 1 in every 10000 children may have a blood lead >40 jug (100 ml)". This standard is, nevertheless, effectively the same as one based on an individual PbB limit of 35-50 jug (100 ml)" as applied in some countries. 

Amidst all this uncertainty the US EPA has set a standard for lead in air of 1.5 jug m based on achieving a target of a population median blood lead for young children (1-5 years) of <15 jug (100 ml) This median has been chosen in order to prevent most children in the US from exceeding a blood lead of 30 jug (100 ml) (see Fig. 7.8). This value has been adopted as a maximum safe blood lead for individual children and is based principally upon the elevation of FEP in the blood as an index of adverse biochemical effect [19]. By adopting this approach they have avoided basing a standard on the uncertain neurobehavioural blood lead relationships. 

As indicated above, this method is extremely popular because of its low cost and ease and rapidity of use. The simplest form of AAS is the flame technique which is of rather limited sensitivity. This may often prove suitable for analysis of lead in air and soils, but is insufficiently sensitive to analyse natural waters or most vegetation samples without a prior preconcentration. For these latter samples, or for short-term air samples flameless atomic absorption is required. Flame techniques are relatively free of interference and matrix effects, but in many applications the method of standard additions [1, 2] is necessary to minimize matrix interferences. Flameless AAS is more subject to interference by background absorption and matrix effects than the flame method, and the use of both deuterium background correction and the standard additions method is usually advisable. 

For example, the lead industry s technical criticisms during the pending mlemaking phase correlated closely with the quantitative significance of EPA s strategy for air lead levels. Industry s statisticians particularly challenged EPA s choice of the ratio relating PbB to air lead. The EPA value of 2 reduced the permissible air lead level to 1.5 units, while a value of 1 or 0.75 would increase the allowed air lead concentration to 3 and 4 pg/m, respectively. EPA s selection of the ratio value of 2 for children was based on the detailed analysis of this topic in Chapter 12 of the final draft of the air lead criteria document. Industry analyses of this ratio were relatively numerous both at the time of document preparation and when the proposed standard for lead in air was offered. 

As an example, if the work requires that the lead-based paint is to be disturbed by drilling a hole in a beam (the beam that has been painted with lead-based paint), will workers be exposed to lead in the air Wliat should be done under the standard to be sure that workers are not being overexposed Under the standards 29 CER 1910.1025, Oeeupational Exposure to Lead in General Industry, and 29 CER 1926.62, Oeeupational Exposure to Lead in Construetion, the following are some eri-teria that should be applied to determine who should be enrolled in the lead program. 

Here, we first discuss whether such semi-closure (which is introduced so that CO2 separation can be undertaken more easily) is likely to lead to higher or lower thermal efficiency, and in this discussion it is helpful to consider recirculation in relation to an air standard cycle (see Fig. 8.4). Fig. 8.4a shows a closed air standard cycle with unit air flow Fig. 8.4b shows an open cycle similarly with unit air flow and an air heater rather than a combustion chamber. The cycles are identical in every respect except that in the former the turbine exhaust air from the turbine is cooled before it re-enters the compressor. In the latter, the turbine exhaust air is discharged to atmosphere and a fresh charge of air is taken in by the compressor. The quantities of heat supplied and the work output are the same for each of the two cycles, so that the thermal efficiencies are identical. 

The hazard from lead is very high, particularly in conditions where the general standard of hygiene is low and lead dust is allowed to accumulate or lead fume is emitted uncontrolled. The recommended permissible limit for concentration of lead in the workplace for lead dust and fume is 0.15 milligrams per cubic meter of air. 

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