Contribution of tap water to chlorate and perchlorate intake: A market basket study

Abstract

The contributions of water to total levels of chlorate and perchlorate intake were determined using food and water samples from a market basket study from 10 locations in Japan between 2008 and 2009. Foods were categorized into 13 groups and analyzed along with tap water. The average total chlorate intake was 333 (min. 193-max. 486) μg/day for samples cooked with tap water. The contribution of tap water to total chlorate intake was as high as 47%-58%, although total chlorate intake was less than 32% of the tolerable daily intake, 1500 μg/day for body weight of 50 kg. For perchlorate, daily intake from water was 0.7 (0.1-4.4) μg/day, which is not high compared to the average total intake of 14 (2.5-84) μg/day, while the reference dose (RfD) is 35 μg/day and the provisional maximum tolerable daily intake (PMTDI) is 500 μg/day for body weight of 50 kg. The highest intake of perchlorate was 84 μg/day, where concentrations in foods were high, but not in water. The contribution of water to total perchlorate intake ranged from 0.5% to 22%, while the ratio of highest daily intake to RfD was 240% and that to PMTDI was 17%. Eight baby formulas were also tested--total chlorate and perchlorate intakes were 147 (42-332) μg/day and 1.11 (0.05-4.5) μg/day, respectively, for an ingestion volume of 1 L/day if prepared with tap water.

Risks for public health related to the presence of chlorate in food

“…The presence of chlorate in the order of mg/kg dry weight in infant/follow-on formula is supported by published studies carried out in Japan (Asami et al, 2013). EFSA is informed that further analyses are currently on-going to confirm the presence of these high levels of chlorate in infant/follow-on formula.…”

“…The amount of water used for cooking was based on described weight yield factor for the different foods; for pasta and rice it was estimated that two parts of water per part of food are used while for dry legumes it should be 1.5 parts of water per part of food (Bognár, 2002). By doing this it is assumed that chlorate is non-volatile and that it remains stable during cooking as it has been recently reported (Asami et al, 2013).…”

“…This sample was not included in the exposure scenarios as it was received at a very late stage during the preparation of this scientific opinion, but is notable because of the high chlorate level. High levels of chlorate (in the order of mg/kg dry weight) have been reported also from infant/follow-on formula in Japan (Asami et al, 2013).…”

Placental transfer of and infantile exposure to perchlorate

“…Perchlorate has also been detected in drinking water and dairy milk (Corley, 2005;Guruge et al, 2011;Her et al, 2010;Kirk et al, 2005;Mantus, 2005;Kannan et al, 2009;Wu et al, 2010). The prevalence of trace levels of perchlorate in food and water results in widespread human exposure (Asami et al, 2013;Blount et al, 2007;Eguchi et al, 2014;Lee et al, 2012). Human exposure to perchlorate is associated with potential health effects because this anion competes with iodine's transport into the thyroid gland by the sodium/iodide symporter (NIS) and can prevent the uptake of iodine into the thyroid, which is essential for thyroid hormone synthesis, normal development, growth, and metabolism (Eguchi et al, 2014;Srinivasan and Viraraghavan, 2009).…”

“…Human exposure to perchlorate is associated with potential health effects because this anion competes with iodine's transport into the thyroid gland by the sodium/iodide symporter (NIS) and can prevent the uptake of iodine into the thyroid, which is essential for thyroid hormone synthesis, normal development, growth, and metabolism (Eguchi et al, 2014;Srinivasan and Viraraghavan, 2009). NIS is expressed in human placenta and in lactating breast tissue, likely as a mechanism for active transport of iodide to the fetus (Bannerman et al, 2006;Dohan and Carrasco, 2003;Logothetopoulus and Scott, 1956). Several studies (Bannerman et al, 2006;Dohan et al, 2007;Tran et al, 2008) found that perchlorate is actively transported across membrane barriers by NIS, raising concerns about the active transport of perchlorate into the fetal circulation during pregnancy and into breast milk (Gu and Coates, 2006;ITRC, 2005;Mantus, 2005), providing two successive routes of exposure during pre-and postnatal periods, respectively.…”