A class action lawsuit was filed against major paint manufactures for damages relative to lead-based paint in all houses in a state that were built before a certain date. Six houses had been selected as exemplars for all houses in the state. As the lawsuit was based upon a presumption that all houses, as represented by these six, were similarly situated, it was necessary to evaluate the six houses to determine if this presumption was correct. Lead-based paint testing had been performed in all the houses by X-ray fluorescence.
We evaluated the testing that had been performed and inspected all of the houses in order to make a lead-based paint hazard assessment for each house, and to document similarities and differences. The houses were similar in that they were all residences and contained lead-based painted surfaces, but there were differences house to house including: age of the house, age of the paint, condition of the house and paint, location and accessibility of lead-based painted surfaces, potential for development of lead-containing dust due to sliding and abrasion of painted surfaces, quantity of lead-based paint, lead concentration in the paint, history of renovation, nature of the occupants, and cleaning and hygiene practices. These differences resulted in very different hazard potential for residents for each house, even if the resident population were the same, which they were not. The population of exemplar houses was too small to determine if there were groupings of houses that would be similar, such as by age, paint history, location (urban vs. suburban), house type (single family detached vs. row house), and construction type (wood frame vs. masonry).
Information developed by this analysis was provided to the trier of fact to inform a decision regarding the similarity of the structures.