Perchlorate exposure from food crops produced in the lower Colorado River region

Abstract

The Colorado River shows low levels of perchlorate derived from aerospace-and defense-related fuel industries once located near the Las Vegas Wash. At sufficiently high dosages perchlorate can disrupt thyroid function by inhibiting uptake of iodide. The Colorado River is the primary source of irrigation water for most food crops grown in Southern California and Southwestern Arizona. The objective of this study was to evaluate potential perchlorate exposure from food crops produced in the lower Colorado River region (LCRR). The major food commodities produced in the region were sampled and perchlorate levels were determined by ion chromatography followed by detection using either conductivity or tandem mass spectrometry, depending on analyte levels. The Monte Carlo module of the Dietary Exposure Evaluation Model (DEEMt) was used to derive an estimate of the 2-day average perchlorate intakes. Data were derived assuming that individuals residing in the LCRR get their fruits and vegetables from within the LCRR as well as from other areas in the United States, or assuming individuals living in the LCRR get their fruits and vegetables from the LCRR only. Perchlorate exposure estimates derived in this study are comparable to exploratory estimates by the US Food and Drug Administration. For infants and children, over 50% of the estimated perchlorate exposure was from milk. The relative impact of vegetables and fruit toward perchlorate exposure increased by age through adulthood. Cumulative perchlorate exposure estimates based on this hypothetical analysis could approach or exceed the NAS reference dose (RfD) for some population groups as drinking water levels exceeded 6 mg/l. However, few individuals are exposed to perchlorate in drinking water at levels above 4 mg/l in the United States and very few would be exposed to perchlorate levels exceeding the RfD, whether consuming food crops from within or outside the LCRR.

Drinking water contribution to aggregate perchlorate intake of reproductive-age women in the United States estimated by dietary intake simulation and analysis of urinary excretion data

“…Consistent with findings from previous studies or perchlorate concentrations in foods (Jackson et al, 2005;Sanchez et al, 2005a;Sanchez et al, 2005b;Murray et al, 2008;Sanchez et al, 2008), results from our dietary simulations suggest that drinking water contamination accounts for a relatively small proportion of total population intake for reproductive-age women in the United States. As shown in Table 5, addition of reasonable assumed drinking water perchlorate distributions increases the central tendency (mean and median) estimates of national perchlorate intakes for reproductive-age women by between approximately 3 and 24%.…”

“…Sanchez et al (2008) also used Monte Carlo analysis to estimate the perchlorate intake distribution for women aged Figure 2. Distribution of intra-day variability in perchlorate excretion (Greer et al, 2002).…”

Thyroid antagonists and thyroid indicators in U.S. pregnant women in the Vanguard Study of the National Children's Study

“…Perchlorate is formed in the atmosphere and can accumulate in the soils of arid regions (Dasgupta et al, 2005). Human exposure sources include contaminated drinking water and consumption of foods containing perchlorate; mainly, milk and high surface area plants such as leafy green vegetables (Murray et al, 2008; Sanchez et al, 2009). Human health concerns are related to the ability of perchlorate to competitively inhibit iodide uptake by the sodium-iodide symporter (NIS) of the thyroid gland (Dohan and Carrasco, 2003; Tonacchera et al, 2004).…”

Method Development and Application To Determine Potential Plant Uptake of Antibiotics and Other Drugs in Irrigated Crop Production Systems

“…Several researchers have demonstrated that certain veterinary antibiotics (e.g., florfenicol, trimethoprim, sulfamethazine, and enrofloxacin) can be taken up into food crops (e.g., wheat, corn, lettuce, barley, and potato) produced on manure-amended soils (22)(23)(24)(25) River to irrigate the approximately 400,000 ha of agricultural crops that are shipped nationally and internationally. Previous research has shown that the Colorado River is contaminated with low levels of perchlorate, and this contaminant can be detected in most agricultural commodities irrigated with this water (27,28). Macrolide antibiotics, pseudoephedrine, and illicit drugs have been identified in several municipal wastewater streams that discharge into the Colorado River (29).…”