Lead coated copper is used by many architects today as a roofing and/or exterior covering material. What are the environmental impacts of the use of this material? Does it contaminate ground water? Does it pose a hazard to installers?

Should we be specifying lead coated copper?

-- Ann Sussman (anns@grahamgund.com), November 14, 1999

Answers

Ann,

I believe this will answer your question:

http://www.yale.edu/ynhti/curriculum/units/1997/7/97.07.05.x.html

-- Dirk Thiele (ke6zuy@excite.com), January 17, 2001.

http://www.professionalroofing.net/past/aug00/qa.asp

-- zack ostroff (zostroff@dt.smithgroup.com), January 29, 2001.

I found the above referenced article interesting, however I feel compelled to point out a few things.

The article appears to have been prepared by a representative of the roofing industry. Unfortunately, the article does not provide any data to support its claim that lead coated copper roofing systems are safe.

The assertion that lead forms an insoluble patina that is impervious to rainwater may not be true. The solubility of lead oxides is dependent on the pH of the solution. Museum conservators use weak solutions of hydrochloric acid to clean lead oxide from artifacts. The use of lead coated copper roofing in areas subject to acidic precipitation may not be a good idea.

I would be much less concerned with how much lead washes from a roof to a groundwater aquifer or a surface water body than with how much lead accumulates in the soil along the building drip line and at the base of the downspout. Lead has some unique properties. One of which is its “stickiness.” Lead washed from a roof system during low intensity rainfalls will most likely accumulate in the soils near the drip line and downspouts. Over time (what is the estimated life span of these roofs?) the lead concentration in these areas can easily build up to toxic levels.

Lead in outdoor soils has been proven to be a source of indoor lead dust.

Under the new EPA standards, lead is considered a hazard if there are greater than: 40 micrograms of lead in dust per square foot on floors; 250 micrograms of lead in dust per square foot on interior window sills and 400 parts per million (ppm) of lead in bare soil in children's play areas or 1200 ppm average for bare soil in the rest of the yard. These levels are applicable regardless of the source of the lead.

As to the hazards to installers, yes it poses a hazard. Consult the OSHA website for the latest regulatory requirements.

-- Mark Wyco (mwyco@theitgroup.com), January 30, 2001.