FIELD DOCUMENTS AND WORK PLANS 1987

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Marley Cooling Tower Page 2 essential element, and because the authors felt that 5.3 mg was a very conservative LOAEL. If a child were to ingest a mouthful of this soil, he might absorb enough copper to cause toxic effects to the gastrointestinal tract, such as gastric pain and diarrhea. This is assuming that the copper is in a readily absorbable form. However, the copper is probably in a complexed form and would not be easily absorbable. The level of chromium is well below the acute NOAEL for rats, which is 14.4 mg/kg/d. The highest soil level of arsenic (253 ppm) is well above the background for Stockton (<0.35 ppm) based on the samples taken by Bob Shlag at two locations remote from the site. If all the arsenic present on the site was arsenic trioxide (trivalent arsenic) the maximum level detected could represent a potentially dangerous level to children ingesting 10 gm of this soil, however, the arsenic is probably in the form of arsenic pentoxide (pentavalent arsenic) rather than arsenic trioxide. Arsenic pentoxide is much less toxic than arsenic trioxide having a human oral LD50 of 55 mg/kg compared to 1.4 mg/kg for arsenic trioxide. Chronic and Subchronic Effects The chromium found in the soil samples was not speciated into Cr VI and Cr III. Cr VI is much more toxic than Cr III. Arsenic and chromium VI are carcinogenic. The other metals are non-carcinogens. TSCD has produced a draft document entitled "The Development of Applied Action Levels for Soil Contact. " In this document it is estimated that an individual is exposed to the contaminants in 0.71 g/day of soil as a lifetime average (0.14 g/d from ingestion and 0.57 g/d from dermal contact) . Human exposure to Cr, Cu and Zn was calculated based on the estimate of 0.71 g/d provided by TSCD. Exposure (mg/d) AIS (mg/d) AIC (mg/d) Chromium .85 1.75 0.35 Copper .47 2.6 2.6 Zinc 1.0 14.7 14.7 AIS and AIC are acceptable intake levels based on subchronic and chronic effects. The AIS is the highest human intake of a chemical that does not cause adverse effects when exposure is short-term (but not acute) . The AIS is usually based on subchronic animal studies. The AIC is the highest human intake of a chemical that does not cause adverse effects when exposure is long-term (lifetime) . The AIC is usually based on chronic animal studies. The AIS and AIC shown for chromium are based on Cr VI toxicity. The corresponding numbers for Cr III are much higher. There are no AIS or AIC numbers for arsenic, because arsenic is a carcinogen. For carcinogens there is no intake level which can be regarded as having no adverse effect. Chromium VI has been shown to be carcinogenic by inhalation but not by ingestion, so there are AIS and AIC values for Cr VI for the oral route, but none for the inhalation route.