Refinishing Old Floors Leads to 'High' Levels of Lead Exposure

With all the attention being paid to lead paint these days, researchers in Wisconsin set out recently to shed light on the danger posed by sanding wood floor varnish in older homes. Their work revealed that refinishing older varnished floors produced "high" levels of lead dust; however, they also learned that the danger posed by this lead dust could be lessened by attaching a HEPA-equipped vacuum to sanding machines.

The researchers found that sanding old varnished surfaces produced lead dust levels that were higher than federal occupancy standards, or dust clearance standards. In addition, they determined that certain varnish refinishing operations can generate lead in air above OSHA standards for workers.

To complete the study, researchers visited 35 homes where Bob Ikens, a report co-author and owner of Ikens Hardwood Floors (Madison, Wis.), was refinishing wood flooring; all homeowners volunteered to have their homes tested for the study. Twenty-six of the homes were built before 1930 and nine were built in 1930 or later. Whereas previous studies of wood floor varnish only looked at lead content in varnishes, for this report the researchers measured for lead before, during and after refinishing work was completed.

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Before sanding, researchers took lead level readings from the floor using an X-ray florescence (XRF) analyzer and by scraping the varnish and sending the sample to a lab for analysis. While sanding work was being performed, researchers collected air samples within the workers' breathing zones to assess lead content in the air; doors and windows were kept closed during sanding. One hour after sanding work was completed, researchers used a HUD-approved dust wipe sampling method to measure the amount of dust present. After the work was performed and all samples collected, the areas were cleaned and made safe for re-occupancy.

Researchers looked at samples both where machines (big machine, edger and buffer) were fitted with HEPA-equipped vacuums and where they were not.

Key findings include:

• The level of lead in a varnish before sanding "significantly correlated" with airborne lead during sanding.
• Machine retrofits resulted in an approximately 54.5 percent reduction in lead in settled dust after sanding was completed.
• When machine retrofits were in use, 90 percent of air samples had no detectable lead.
• Pre-refinishing testing found more lead on stairs that on floors, perhaps because stairs most often still wore original varnish. As a result, refinishing stairs resulted in higher settled lead dust levels than refinishing floors.
• Hand scraping on stairs generated higher lead-in-air levels than power sanding on floors. Also, researchers determined that hand-scraping will likely produce lead in the air above OSHA-permissible levels when an initial lead varnish measurement exceeds 0.18 mg/square-centimeter.
• It is more difficult to get a good vacuum seal on edgers and thus more difficult to control lead in dust when refinishing stairs than when refinishing floors.
• It is more accurate to measure lead in varnish using a scrape sample rather than relying on a reading from a portable XRF analyzer. This is because the federal standards used to calibrate XRF instruments are not sensitive enough to identify lead in varnish that could cause hazards.

The full report "Lead Exposures from Varnished Floor Refinishing" can be purchased and downloaded here. An abstract of the report can be read here.

A 2001 article included research that indicated 18 percent of floor varnish samples exceeded the federal legal definition for lead-based paint of 5000 parts per million (ppm), and 72 percent exceeded the U.S. Consumer Product Safety Commission's limit for lead in new paint of 600 ppm.