HEALTH CONSULTATION

FOR RESIDENTIAL SOIL

VEGA BAJA SOLID WASTE DISPOSAL
RIO ABAJO WARD/LA TROCHA, VEGA BAJA COUNTY, PUERTO RICO

DISCUSSION

The chemical of concern at the Vega Baja landfill is lead; therefore, only the lead levels in soil will be reported here. Thelevel of lead in the top two inches of soil ranges from 7 ppm to 26,300 ppm. The level of lead in subsurface soil, the top2 feet, ranges from 18 ppm to 2,540 ppm. Soil samples taken in areas near the landfill (that is background samples) rangefrom 7 ppm to 81 ppm. Twenty-nine properties have lead levels that exceed 1,000 ppm.

Table 1 shows the address and range of lead levels for those properties that exceeded 400 ppm lead in soil. The resultscome from the July/August 1996 and the April 1997 soil samples.

* all surface soil samples are from the top 2 inches of soil
** all subsurface soil samples are from the top 2 feet of soil

Children have been living on the Vega Baja site for years. Children, especially pre-school children, might be exposed to smallamounts of lead when they accidentally swallow soil and dust that cling to their hands. EPA has developed a biokinetic model(Integrated Exposure Uptake Biokinetic {IEUBK} Lead Model) that relates multimedia lead exposure to a probability distributionof blood lead levels in exposed children. Based on historical application of EPA's IEUBK model at other hazardous waste sitesin the United States, exposure to lead in soil above 400 ppm could shift the probability distribution of blood lead levels so thatgreater than 5% of the children could have blood lead levels above 10 micrograms per deciliter (µg/dL), the Centers for DiseaseControl and Prevention's level of concern. The shift in blood lead distribution is more pronounced when soil lead levels are above1,000 ppm, resulting in a greater probability of children attaining blood lead levels that are known to cause harmful effects. Insupport of EPA's IEUBK model, slope factors from epidemiological studies that correlate soil lead levels to blood lead levels showan increase of 1 to 8 µg/dL of blood lead in children living in residential areas with lead-contaminated soil for every 1,000 ppm lead in soil (2,3).

PREQB resampled three properties that previously showed very high lead levels (12,700 ppm to 26,300 ppm). The results ofadditional soil samples from the same location on those three properties showed lead levels ranging from approximately 100 ppmto 4,000 ppm. Lead levels from soil samples in other parts of the same properties showed a similar range.

In December 1996, the Puerto Rico Department of Health (DOH) conducted blood lead testing in some children ages 1 to 6 yearswho live on or near the site. The blood lead tests of the children sampled showed levels up to 5.7 µg/dL with a mean of 1.9 µg/dL(4). While the current blood lead results did not find significant lead exposure, the results should not be used to decide that the leadcontamination at the site is not a public health threat. The reasons are

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