Residential mercury spills from gas regulators.

Many older homes are equipped with mercury-containing gas regulators that reduce the pressure of natural gas in the mains to the low pressure used in home gas piping. Removal of these regulators can result in elemental mercury spills inside the home. In the summer of 2000, mercury spills were discovered in the basements of several Chicago-area homes after removal of gas regulators by gas company contractors. Subsequent inspections of approximately 361,000 homes by two northern Illinois gas companies showed that 1,363 homes had residential mercury contamination. Urine mercury screening was offered to concerned residents, and results of urine bioassays and indoor mercury air measurements were available for 171 homes. Six of these 171 homes (3.5%) had a cumulative total of nine residents with a urine mercury > or = 10 microg/L. The highest urine mercury concentration observed in a resident was 26 microg/L. Positive bioassays were most strongly associated with mercury air concentrations > 10 microg/m3 on the first floor [odds ratio (OR) = 21.4 ; 95% confidence interval (CI) , 3.6-125.9] rather than in the basement (OR = 3.0 ; 95% CI, 0.3-26) , and first-floor air samples were more predictive of positive bioassays than were basement samples. Overall, the risk of residential mercury contamination after gas regulator removal ranged from 0.9/1,000 to 4.3/1,000 homes, depending on the gas company, although the risk was considerably higher (20 of 120 homes, 16.7%) for one of the contractors performing removal work for one of the gas companies. Gas companies, their contractors, and residents should be aware of these risks and should take appropriate actions to prevent these spills from occurring and remediate them if they occur.

Urinary p-nitrophenol as a biomarker of household exposure to methyl parathion.

Methyl parathion (MP) is an organophosphate pesticide illegally applied to the interiors of many hundreds of homes throughout the United States by unlicensed pesticide applicators. Public health authorities developed a protocol for investigating contaminated homes and classifying their need for public health interventions. This protocol included environmental screening for MP contamination and 1-day biomonitoring (a.m. and p.m. spot urine samples) of household members for p-nitrophenol (PNP), a metabolite of MP. The variability of urinary PNP excretion under these exposure conditions was unknown. We collected a.m. and p.m. spot urine samples for 7 consecutive days from 75 individuals, who were members of 20 MP-contaminated households in the greater Chicago, Illinois, area, and analyzed them for PNP. We also assessed the ability of the 1-day sampling protocol to correctly classify exposed individuals and households according to their need for public health interventions, assuming that 1 week of sampling (14 urinary PNPs) represented their true exposure condition. The coefficient of variation of log urinary PNPs for individuals over the course of 7 days of a.m. and p.m. sampling averaged about 15%. Adjusting for urinary excretion of creatinine improved reproducibility of urinary PNPs among children but not among adults. The 1-day protocol correctly classified true risk category in 92% of individuals and 85% of households. The data contained in this study can be used to refine what is already a reasonable and effective approach to identifying MP-exposed households and determining the appropriate public health intervention.