Perchlorate, an iodide uptake inhibitor, is increasingly being detected in new places and new matrices. Perchlorate contamination has been attributed largelyto the manufacture and use of ammonium perchlorate (the oxidizer in solid fuel rockets) and/or the earlier use of Chilean nitrate as fertilizer (approximately 0.1% perchlorate). However, there are regions such as the southern high plains (Texas Panhandle) where there is no clear historical or current evidence of the extensive presence of rocket fuel or Chilean fertilizer sources. The occurrence of easily measurable concentrations of perchlorate in such places is difficult to understand. In the southern high plains groundwater, perchlorate is better correlated with iodate, known to be of atmospheric origin, compared to any other species. We show that perchlorate is readily formed by a variety of simulated atmospheric processes. For example, it is formed from chloride aerosol by electrical discharge and by exposing aqueous chloride to high concentrations of ozone. We report that perchlorate is present in many rain and snow samples. This strongly suggests that some perchlorate is formed in the atmosphere and a natural perchlorate background of atmospheric origin should exist.

Perchlorate inhibits iodide uptake and may impair thyroid and neurodevelopment in infants. Recently, we unambiguously identified the presence of perchlorate in all seven brands of dairy milk randomly purchased from grocery stores in Lubbock, TX. How widespread is perchlorate in milk? Perchlorate in 47 dairy milk samples from 11 states and in 36 human milk samples from 18 states were measured. Iodide was also measured in a number of the samples. Perchlorate was detectable in 81 of 82 samples. The dairy and breast milk means were, respectively, 2.0 and 10.5 microg/L with the corresponding maximum values of 11 and 92 microg/L. Perchlorate is present in virtually all milk samples, the average concentration in breast milk is five times higher than in dairy milk. Although the number of available measurements are few at this point, for breast milk samples with a perchlorate content greater than 10 microg/L, the iodide content is linearly correlated with the inverse of the perchlorate concentration with a r2 of >0.9 (n = 6). The presence of perchlorate in the milk lowers the iodide content and may impair thyroid development in infants. On the basis of limited available data, iodide levels in breast milk may be significantly lower than it was two decades ago. Recommended iodine intake by pregnant and lactating women may need to be revised upward.

Abstract. A Nationwide Nitrogen Deposition Monitoring Network (NNDMN) containing 43 monitoring sites was established in China to measure gaseous NH3, NO2, and HNO3 and particulate NH4+ and NO3− in air and/or precipitation from 2010 to 2014. Wet/bulk deposition fluxes of Nr species were collected by precipitation gauge method and measured by continuous-flow analyzer; dry deposition fluxes were estimated using airborne concentration measurements and inferential models. Our observations reveal large spatial variations of atmospheric Nr concentrations and dry and wet/bulk Nr deposition. On a national basis, the annual average concentrations (1.3–47.0 μg N m−3) and dry plus wet/bulk deposition fluxes (2.9–83.3 kg N ha−1 yr−1) of inorganic Nr species are ranked by land use as urban > rural > background sites and by regions as north China > southeast China > southwest China > northeast China > northwest China > Tibetan Plateau, reflecting the impact of anthropogenic Nr emission. Average dry and wet/bulk N deposition fluxes were 20.6 ± 11.2 (mean ± standard deviation) and 19.3 ± 9.2 kg N ha−1 yr−1 across China, with reduced N deposition dominating both dry and wet/bulk deposition. Our results suggest atmospheric dry N deposition is equally important to wet/bulk N deposition at the national scale. Therefore, both deposition forms should be included when considering the impacts of N deposition on environment and ecosystem health.

Storm surge associated with Hurricane Katrina and the breach of levees protecting New Orleans, Louisiana allowed floodwaters from Lake Pontchartrain to inundate 80% of the city. Environmental samples were collected during September 16-18, 2005 to determine immediate human and wildlife health hazards from pathogens and toxicants in the floodwaters. Baseline information on potential long-term environmental damage resulting from contaminants in water and sediments pumped into Lake Pontchartrain was also collected. Concentrations of aldrin, arsenic, lead, and seven semivolatile organic compounds in sediments/soils exceeded one or more United States Environmental Protection Agency (USEPA) thresholds for human health soil screening levels and high priority bright line screening levels. High numbers of Aeromonas spp., pathogenic Vibrio spp., and other coliform bacteria were found in floodwater samples. Alligator and snake tissues did not contain excessive toxicant concentrations. Initial findings suggest numerous environmental contaminants are present in New Orleans and support the need for further evaluation of the extent of those threats.

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