A CONTROLLED TRIAL OF THE EFFECT OF HEPA VACUUMING ON CHILDHOOD LEAD-EXPOSURE

The benefit of repeated use of high efficiency particulate air (HEPA) vacuum cleaners was studied in the lead/zinc smelter community of Trai l, British Columbia. Fifty-five treatment homes received thorough HEPA vacuuming of floor areas once every six weeks for 10 months, while 56 control homes did not. the geometric mean blood lead level declined f rom 11.9 to 11.0 mu g/dL in the treatment group (p=0.06) and from 11.3 to 10.7 in the control group (p=0.23). The net effect of vacuuming on blood lead level (0.3 mu g/dL) was neither clinically nor statistical ly significant. Geometric mean lead loading on carpet surfaces decline d from 0.56 to 0.36 mg/m(2) in the treatment group (p=0.01) and from 0 .27 to 0.23 mg/m(2) in the control group (p=0.21). The net difference between groups (0.16 mg/m(2), p=0.02) fell short of the estimated 0.30 mg/m(2) required for clinical significance. A survey of participants and an ancillary investigation of recontamination provided insight int o the factors that influence indoor lead exposure and indicated that m ore frequent vacuuming might be beneficial in some cases.