Analysis of dialkylphosphate urinary metabolites of organophosphorus insecticides has been used to estimate dose in nonoccupationally exposed populations, including children. Analytical methods must continue to be improved in order to accurately and reproducibly measure less than 10 ng/mL of these metabolites. Dialkyl phosphates are commonly determined as their pentafluorobenzyl bromide derivatives via gas chromatography (GC) with flame photometric detection. Presented here is an improved method for precleanup of urine using solid-phase extraction, followed by derivatization and GC analysis. The method includes the quantitative determination of the following dialkyl phosphate metabolites: dimethylphosphate, diethylphosphate, dimethylthiophosphate, diethylthiophosphate, and dimethyldithiophosphate. Additional cleanup of urine samples allows for increasing sample size and improving sensitivity while minimizing interferences and variability associated with derivatization. Sample aliquot size was 5 mL with limits of quantitation of 10 ng/mL of urine for dimethylphosphate and diethylphosphate and 2 ng/mL of urine for dimethylthiophosphate, diethylthiophosphate, and dimethyldithiophosphate. This level of method sensitivity allows for quantitative determination of trace dialkyl phosphates in approximately 75% of individuals in nonoccupationally exposed populations. This streamlined method increases sample throughput, provides a clean extract for analysis, and requires no custom glassware.

Radiological sampling and analysis performed under the National Interim Primary Drinking Water Regulations were evaluated for the U.S. Environmental Protection Agency (EPA) Office of Drinking Water to consider whether any changes should be recommended. The authors reviewed the analytical screening scheme; sample collection, storage and analysis procedures; selection of analytical methods; reliability of results; and possible future needs. The main problem in the program has been dependence on a screening scheme of gross alpha-particle activity measurement and 226Ra analysis for predicting elevated 228Ra levels to determine compliance with the maximum contaminant level (MCL) for Ra. In some aquifers, 228Ra levels have been found to be unrelated to 226Ra levels. Several alternatives are discussed to eliminate this problem. A secondary problem is that the measurement for assuring compliance with the MCL for gross alpha-particle activity minus Ra, Rn and U uses chemical U analysis and assumes equilibrium of 238U and 234U. Because some ground waters are known to be at disequilibrium, radiometric U analysis is needed for those gross alpha-particle activities and chemical U values that could result in an erroneous conclusion relative to the MCL. In addition, studies were recommended for determining analytical uncertainties and assuring reliable sampling and sample maintenance; improvements in the system for accepting methods were suggested; and methods were identified for several radionuclides not currently in the analytical program that may be needed to assure absence of elevated radiation doses and could be useful for identifying trace contaminants.

Iowa towns of 1000-10,000 population, whose water came solely from wells of over 500 feet (152 meters) in depth and was not treated by a process that would remove radioactivity, were identified. Age-adjusted, sex-specific, cancer incidence rates were determined for these towns for the years 1969-1978 (excluding 1972) and related to the mean level of radium-226 in the municipal water supply. Incidence rates of cancers of the lung and bladder among males and of cancers of the breast and lung among females were higher in towns with a radium-226 level in the water supply exceeding 5.0 pCi/l. A gradient of increasing cancer incidence associated with rising radioactivity level for three time periods was also seen for lung cancer among males. The associations between cancer incidence and radioactivity of water supply could not be explained by smoking patterns, water treatment factors, other water quality measurements, or known socio-demographic features.

No abstract

The University Hygienic Laboratory has been performing radiochemical analyses on drinking water in the state of Iowa for over 20 yr. Approximately one half of the 1250 community water supplies that exist in Iowa have been sampled roughly once every 3 yr for the past decade. Originally, raw and finished waters that showed a gross alpha activity of greater than or equal to 3.0 pCi/L were analyzed for 226Ra, but starting in July 1976, finished waters were analyzed for both 226Ra and 228Ra if the gross alpha activity was greater than or equal to 2.0 pCi/L. As of 10 June 1981, 604 community water supplies had submitted composited samples that have been analyzed for gross alpha, 226Ra, and 228Ra concentrations in compliance with the federal Safe Drinking Water Act (Public Law 93-523). Approximately 10% of these supplies were found to exceed the EPA-established maximum contaminant level (MCL) for 226Ra plus 228Ra of 5 pCi/L. The results revealed, consistent with several other investigators (Mc81; Mi80; Mic80), that some supplies had higher concentrations of 228Ra than of 226Ra. It was also concluded, in agreement with McCurdy and Mellor (Mc81), that some ground water samples cannot be accurately measured for gross alpha activity due to their high dissolved solids content.