Dust Clearance

The mucociliary clearance mechanism is generally recognised as a defence against infectious agents and a means to remove inhaled particulate matter. Inhaled particles reach different locations in the lung depending on their size. Above 5 [an, the conducting airways filter dusts, where ciliated and mucous cells cooperate and waft the particles upwards. 

BalAshAzy and Hofmann (1995) explored the effects of asymmetry in airway diameter, branching angle, and flow division on both inspiratory and expiratory particle deposition patterns for various particle sizes and flow rates. 

Besides the intensity and duration of the exposure, the period of life at the beginning of the dusty job may be important in the susceptibility of a person (Worth and Muysers 1967). At high levels of exertion children had a greater percentage of total deposition in the tracheobronchial region than do adults for equivatent levels of activity (Schum et al. 1994). Deposition rate depends on the deposition 

Whereas much is known about clearance of particles from the airways, less is known about the interaction between the surface of the particles and the cellular substrate of the clearing mechanism. 

The surface of airway epithelium is covered by airway surface liquid, the physical properties of which are determined by active ions and water transport. Baconnais et al. (1997) developed a technique to study the elemental composition of Na, Mg, P, S, Cl, K and Ca of native airway surface hquid collected in germ-free mice. 

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A certified renovator must visually verify the cleanup in any external areas, including the ground and any exterior windowsills. Alternatively, if the owner or any law requires dust clearance sampling, that can substitute for the visual inspection. The renovator must re-clean if any dust or debris remains. ... 

Typically, when an abatement is performed, the housing is either unoccupied or the occupants are temporarily relocated to lead-safe housing until the abatement has been demonstrated to have been properly completed through dust clearance testing. Carpet in the housing is usually removed as part of the abatement because it is difficult to demonstrate that it is free of lead-based paint hazards. Uncarpeted floors that have not been replaced during the abatement may need to be refinished or sealed in order to... 

In contrast to the 2006 Proposal, this final rule does not allow dust clearance sampling in lieu of post-renovation cleaning verification, except in cases where the contract between the renovation firm and the property owner or another federal, state, territorial, tribal, or local regulation requires dust clearance sampling by a certified sampling professional and requires the renovation firm to clean the work area until it passes clearance. 

Except as provided in 40 CER 745.85(c), this final rule does not allow dust clearance sampling to be performed in lieu of post-renovation cleaning verification. However, some property owners may still choose to have dust clearance sampling performed after the renovation. Dust sampling technicians certified in accordance with this final rule will be available to perform dust clearance sampling after renovations and for the purposes of HUD s Lead-Safe Housing Rule. 

Therefore, the final rule does not require dust clearance sampling after any renovations, nor does it allow the signs... 

A few commenters contended that EPA should not require dust clearance testing because there is a difference between abatement, which is intended to eliminate lead-based paint hazards, and renovations in which the focus should be to not create any new lead-based paint hazards. Some commenters asserted that dust clearance testing should not be required because this would result in the renovator being responsible for existing... 

For abatements, clearance testing and clearance are used to minimize potential exposure by eliminating lead-based paint hazards after completion of the job. Clearance acts as the means to ensure that minimization, and signal the end of the job. For renovations, given the presence of residents, the concern is for potential exposure both during and after the job. Dust clearance testing and clearance would only address the second part of the exposure equation. Thus, dust clearance testing conducted after renovation activities have been completed would not provide the equivalent determination of potential exposure that it does for abatement. 

Thus, EPA believes that dust clearance sampling is a poor fit for renovation work for a variety of reasons, including the greater expense associated with clearance testing, the time necessary to obtain the results of the testing and the consequent delay in the completion of the job, and the potential to expand the scope of the renovation. 

One commenter contended that cleaning after the renovation activity until the worksite passed a visual inspection was the most important determinant of whether a job would pass a dust clearance test. In support of this contention, the commenter cited the Reissman study (Journal of Urban Health, 79(4) 502-11, 2005). The commenter contended that the study demonstrates that when there was no visible dust and debris present after completion of renovation or remodeling activity, there was no added risk of a child having an elevated blood-lead level as compared to the risk for children living in homes where there was no reported renovation or remodeling work. 

EPA proposed to allow optional dust clearance sampling at the completion of renovation activities instead of the postrenovation cleaning verification described in 745.85(b). Some commenters agreed that the decision whether to perform clearance at the conclusion of the job should be left to the home-owner. One commenter asked EPA to require that, if a resident arranged for clearance testing and found lead hazards, the contractor would have to reclean to the resident s satisfaction. 

As discussed, dust clearance sampling and cleaning verification are not surrogates and EPA is not requiring renovation... 

In response to these comments, EPA has further considered the issue and decided to allow dust clearance sampling instead of cleaning verification only in certain limited situations. EPA agrees with the commenters that, if the rule were to allow clearance sampling instead of verification, EPA would have to require the renovator to achieve clearance, otherwise there would be no check on whether the renovation had been safely performed. HUD s Lead-Safe Housing Rule requires clearance to be achieved in many situations, as do several states. For example, the State of New Jersey requires dust clearance sampling and clearance in certain situations in multi-unit rental housing. 

EPA will allow the renovation firm to use both dust clearance testing and clearance instead of the cleaning verification step. 

EPA disagrees that it should modify its proposed rule to allow cleanup with a non-HEPA vacuum. EPA has determined that the weight of the evidence provided by various studies demonstrates that the HEPA vacuums consistently removed significant quantities of lead-based paint dust and reduced lead loadings to lower levels then did other vacuums. While there may be some vacuums that are as effective as HEPA vacuums, EPA has not been able to define quantitatively the specific attributes of those vacuums. That is, EPA is not able to identify what criteria should be used to identify vacuums that are equivalent to HEPA vacuums in performance. Thus, EPA does not believe that it can identify what types of vacuums can be used as substitutes for HEPA vacuums. EPA also notes that non-HEPA vacuums that perform as well as HEPA vacuums may not be less expensive than HEPA vacuums. For these reasons, EPA has determined that modifying its proposed rule to allow cleanup with non-HEPA vacuums would compromise the level of lead dust clearance achieved by the standard, and might not result in meaningful cost reductions. 

Guidelines for clearance following paint abatement are probably inadequate for dust abatement. These guidelines were most likely selected because they are the lowest reasonable level attainable with paint abatement methods producing large amounts of dust. The uncertainty over dust clearance stems from the fact that there is very little information about the relationship between dust loading (pg/m ) and lead exposure. 

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