Relative source contributions for perchlorate exposures in a lactating human cohort.

Perchlorate is an iodine-uptake inhibitor and common contaminant of food and drinking water. Understanding the amount of perchlorate exposure occurring through non-water sources is essential for accurate estimates of human exposure levels, and establishment of drinking water limits for this pervasive contaminant. The study objective was to determine the amount of perchlorate intake derived from diet rather than water. Subjects provided drinking water samples, detailed fluid-intake records, 24h urine collections and four milk samples for nine days. Samples were analyzed for perchlorate by isotope dilution ion chromatography-tandem mass spectrometry. Amounts of perchlorate derived from drinking water and dietary sources were calculated for each individual. Water of local origin was found to contribute a minor fraction of perchlorate intake. Estimated fraction intake from drinking water ranged from 0 to 36%. The mean and median dose of perchlorate derived from non-water sources by lactating women was 0.18 µg/kg/day (range: 0.06 to 0.36 µg/kg/day.) Lactating women consumed more fluid (mean 2.424 L/day) than has been assumed in recent risk assessments for perchlorate. The data reported here indicate that lactating women may be exposed to perchlorate through dietary sources at markedly higher levels than estimated previously. Exposures to perchlorate from non-water sources may be higher than recent estimates, including those used to develop drinking water standards.

Perchlorate, iodine supplements, iodized salt and breast milk iodine content.

This study was undertaken to determine if increasing maternal iodine intake through single dose tablets will decrease breast milk concentrations of the iodine-uptake inhibitor, perchlorate, through competitive inhibition. We also sought to determine if the timing of supplementation influences the fraction of iodine excreted in milk versus urine and to compare the effectiveness of iodized salt as a means of providing iodine to breastfed infants. Thirteen women who did not use supplements, seven of whom used iodized salt and six of whom used non-iodized salt, submitted four milk samples and a 24-h urine collection daily for three days. Women repeated the sampling protocol for three more days during which ~150µg of iodine were taken in the evening and again for three days with morning supplementation. Samples were analyzed using isotope-dilution inductively-coupled plasma-mass spectrometry for iodine and isotope-dilution ion chromatography-tandem mass spectrometry for perchlorate. No statistically significant differences were observed in milk iodine or perchlorate concentrations during the two treatment periods. Estimated perchlorate intake was above the U.S. National Academy of Sciences suggested reference dose for most infants. Single daily dose iodine supplementation was not effective in decreasing milk perchlorate concentrations. Users of iodized salt had significantly higher iodine levels in milk than non-users. Iodized salt may be a more effective means of iodine supplementation than tablets.

Trace iodine quantitation in biological samples by mass spectrometric methods: the optimum internal standard.

Accurate quantitation of iodine in biological samples is essential for studies of nutrition and medicine, as well as for epidemiological studies for monitoring intake of this essential nutrient. Despite the importance of accurate measurement, a standardized method for iodine analysis of biological samples is yet to be established. We have evaluated the effectiveness of (72)Ge, (115)In, and (129)I as internal standards for measurement of iodine in milk and urine samples by induction coupled plasma mass spectrometry (ICP-MS) and of (35)Cl(18)O(4)(-), (129)I(-), and 2-chlorobenzenesulfonate (2-CBS) as internal standards for ion chromatography-tandem mass spectrometry (IC-MS/MS). We found recovery of iodine to be markedly low when IC-MS/MS was used without an internal standard. Percent recovery was similarly low using (35)Cl(18)O(4) as an internal standard for milk and unpredictable when used for urine. 2-Chlorobenzebenzenesulfonate provided accurate recovery of iodine from milk, but overestimated iodine in urine samples by as much as a factor of 2. Percent recovery of iodine from milk and urine using ICP-MS without an internal standard was approximately 120%. Use of (115)In predicted approximately 60% of known values for both milk and urine samples. (72)Ge provided reasonable and consistent percent recovery for iodine in milk samples (approximately 108%) but resulted in approximately 80% recovery of iodine from urine. Use of (129)I as an internal standard resulted in excellent recovery of iodine from both milk and urine samples using either IC-MS/MS and ICP-MS.

Intake of iodine and perchlorate and excretion in human milk.

Perchlorate, thiocyanate, and iodine excretion in urine and milk of 13 breastfeeding women was investigated and the results were interpreted by a model of parallel/competitive transport of these species bythe sodium iodide symporter. For each species i, we assumed physiological homeostasis, where i(T,in) equals the corresponding total excretion in urine and milk (i(e,u) + i(e,m)). The fraction of the total excretion that appeared in milk f(I,m) was measured and ranged from 0.394-0.781, 0.018-0.144, and 0.086-0.464 for perchlorate,thiocyanate, and iodine, respectively. The corresponding median values were 0.541, 0.053, and 0.177, respectively. The selectivity factors of perchlorate over iodide transport, and thiocyanate over iodide transport, defined as f(PC,m)/ f(I,m), and f(SCN,m)/ f(I,m), respectively, were 3.14 +/- 1.20 and 0.27 +/- 0.26 while PC(T,in), SCN(T,in), and I(T,in) among individuals varied 4.9, 5.0, and 8.4x, respectively. These transport selectivities are an order of magnitude lower than those indicated by in vitro studies, suggesting that the impact of both these anions on inhibiting iodide transport in milk may have been overestimated in the extant literature. On the other hand, our results showed that 12 of 13 infants did not have an adequate intake of iodine as defined by the Institute of Medicine and 9 out of 13 infants were likely ingesting perchlorate at a level exceeding the reference dose suggested bythe National Academy of Science panel.

Atmospheric ozone measurement with an inexpensive and fully automated porous tube collector-colorimeter.

The bleaching action of ozone on indigo and related compounds is well known. We describe sensitive automated instrumentation for measuring ambient ozone. Air is sampled around a porous polypropylene tube filled with a solution of indigotrisulfonate. Light transmission through the tube is measured. Light transmission increases as O(3) diffuses through the membrane and bleaches the indigo. Evaporation of the solution, a function of the RH and the air temperature, can, however cause major errors. We solve this problem by adding an O(3)-inert dye that absorbs at a different wavelength. Here we provide a new algorithm for this correction and show that this very inexpensive instrument package (controlled by a BASIC Stamp Microcontroller with an on-board data logger, total parts cost US$ 300) provides data highly comparable to commercial ozone monitors over an extended period. The instrument displays an LOD of 1.2ppbv and a linear span up to 300ppbv for a sampling time of 1min. For a sampling time of 5min, the respective values are 0.24ppbv and 100ppbv O(3).

Iodine nutrition: iodine content of iodized salt in the United States.

Adequacy of iodine nutrition in the United States has lately been of concern. A major source of dietary iodine for the U.S. population is iodized salt. The U.S. Food and Drug Administration (USFDA) recommends 60-100 mg Kl/kg salt, equivalent to 46-76 mg l/kg salt. All U.S. iodized salt contains 45 mg l/kg according to labels. We collected samples of table salt from freshly opened containers from U.S. volunteers. A sample was sent to us when the can was first purchased. Subsets of volunteers sent further samples when the salt container became half-empty through normal use and a further final sample when the container was nearly finished. We also looked at iodine distribution homogeneity within individual containers, loss of iodine from salt upon exposure to humidity and sunlight, and upon short-term heating (dry and in solution) as may be encountered in cooking. Measurements were made in 0.01% w/v salt solutions by induction coupled plasma-mass spectrometry with 72Ge as an internal standard. The median and mean (+/-sd) I content in freshly opened top-of-the-can salt samples was 44.1 and 47.5 +/- 18.5 mg/kg (n=88, range 12.7-129 mg l/kg) and geometric mean and standard deviation of 44.70 and 1.41. Forty-seven of 88 samples fell below the USFDA recommended I content while 6 exceeded it. The homogeneity in a single can of salt varied greatly: in 5 samples taken from the same container from different depths, the iodine content varied by as little as 1.2x (8.3% coefficient of variance (CV)) to as much as 3.3x (49.3% CV) from one container/brand to another. Iodine is significantly lost upon high humidity storage but light or dry heat has little effect. There is much recent literature on iodine sufficiency and uptake inhibitors; there is also much misinformation and disinformation. We review the relevant literature and discuss our results with reference to the United States.

Creatinine adjustment of spot urine samples and 24 h excretion of iodine, selenium, perchlorate, and thiocyanate.

Creatinine (CR) adjustment is widely used for the estimation of urinary 24 h excretion from spot urine samples. We have compared CR-adjusted values for urinary iodine, selenium, perchlorate, and thiocyanate to measured 24 h excretion. The urine samples were collected from a cohort of 14 breastfeeding mothers with both spot samples and 24 h collection, 52 24 h and spot sample pairs where the 24 h CR value fell within the "normal" adult female CR excretion range of 0.6-1.6 g/day were considered for this analysis. In addition, a nonlactating female and a male subject provided all micturitions for 1 and 5 days, respectively. Creatinine was analyzed with a Jáffe reaction-based automated analyzer. Iodine and selenium were determined with induction coupled plasma-mass spectrometry (ICP-MS). Perchlorate and thiocyanate were measured with ion chromatography (IC)-isotope dilution tandem mass spectrometry (MS/MS). Creatinine-adjusted values were poor substitutes of the actual 24 h excretion values (average deviation +/-69, 78, 105, and 104% for iodine, selenium, perchlorate, and thiocyanate, respectively.). Over a 5 day period, the 24 h iodine excretion predicted based on creatinine adjustment of spot samples for the same individual deviated between -83.5 to +101% from the actual measured value, the minimum absolute error being 2.5%. Creatinine adjustment for estimation of 24 h excretion from spot samples was not effective for iodine, selenium, perchlorate, or thiocyanate.

Postcolumn concentration in liquid chromatography. On-line eluent evaporation and analyte postconcentration in ion chromatography.

On-line sample concentration by evaporation through a narrow-bore membrane tube is described. The device can be deployed just prior to the detector or the sample may be concentrated prior to injection. As solution flows through a solvent-permeable membrane tube, (heated) drying gas (nitrogen/air) flows outside it to remove the solvent. The removal rate increases with increasing sample residence time, drying gas flow rate, and temperature. Various membranes and three concentrator designs (a rectangular maze, a serpentine and a filament-filled helix, the last performing the best) were fabricated and tested for post- and preseparation applications in suppressed anion chromatography. An order of magnitude concentration factors are readily obtained. The present system involves active mass transport radially outward through the walls of a tube. This is a system in which many of the traditional paradigms of flow through a tubular conduit no longer hold true. Because the flow rate continuously varies along the tube, residence time does not scale linearly with residence volume or conduit length. The effects of such mass transport on the parabolic velocity profile of laminar flow remain unknown.

Temporal patterns in perchlorate, thiocyanate, and iodide excretion in human milk.

BACKGROUND: Perchlorate and thiocyanate interfere with iodide uptake at the sodium-iodide symporter and are potential disruptors of thyroid hormone synthesis. Perchlorate is a common contaminant of water, food, and human milk. Although it is known that iodide undergoes significant diurnal variations in serum and urinary excretion, less is known about diurnal variations of milk iodide levels. OBJECTIVES: Variability in perchlorate and thiocyanate excretion in human milk has not been examined. Our objective was to determine variability of perchlorate, thiocyanate, and iodide in serially collected samples of human milk. METHODS: Ten lactating women were asked to collect six milk samples on each of 3 days. As an alternative, subjects were asked to collect as many milk samples as comfortably possible over 3 days. Samples were analyzed for perchlorate, iodide, and thiocyanate by ion chromatography coupled with mass spectrometry. RESULTS: Individual perchlorate, iodide, and thiocyanate levels varied significantly over time; there was also considerable variation among individuals. The iodide range, mean +/- SD, and median for all samples (n = 108) were 3.1-334 microg/L, 87.9 +/- 80.9 microg/L, and 55.2 microg/L, respectively. The range, mean +/- SD, and median of perchlorate in all samples (n = 147) were 0.5-39.5 microg/L, 5.8 +/- 6.2 microg/L, and 4.0 microg/L. The range, mean +/- SD, and median of thiocyanate in all samples (n = 117) were 0.4 -228.3 microg/L, 35.6 +/- 57.9 microg/L, and 5.6 microg/L. The data are not symmetrically distributed; the mean is higher than the median in all cases. CONCLUSIONS: Iodine intake may be inadequate in a significant fraction of this study population. Perchlorate and thiocyanate appear to be common in human milk. The role of these chemicals in reducing breast milk iodide is in need of further investigation.

Perchlorate in dairy milk. Comparison of Japan versus the United States.

Perchlorate has been considered a potential threat to human health, especially to developing infants and children due to its ability to inhibit iodide uptake by the sodium iodide symporter (NIS) of the thyroid. Although the U.S. has been the prime focus of perchlorate contamination, at least some of the similar sources of perchlorate exist across the world, and it has been detected in many types of foods and beverages worldwide. We present here perchlorate data from cow's milk samples from Japan (mean 9.4 +/-2.7 microg/L, n = 54), which are higher on average than those found in U.S. dairy milk samples reported by a 2004 Food and Drug Administration (FDA) study (5.9+/-1.8 microg/L, n= 104).

Perchlorate in the United States. Analysis of relative source contributions to the food chain.

Perchlorate has been considered by some a potential threat to human health, especially to developing infants and children because it may inhibit iodide uptake by the sodium iodide symporter (NIS) of the thyroid. In the United States, during the last several decades, environmental perchlorate has had three recognized sources stemming from (a) its use as an oxidizer (including in rocket propellants), (b) its presence in Chilean nitrate fertilizer (CNF), and (c) natural production. An analysis of the relative source strengths and how they may influence entry into the food chain has not been conducted. Averaged over the last --60 years, we estimate that the source strengths have been (a) 10.6, (b) 0.75, and (c) 0.13-0.64 Gg/y for the United States as a whole. Of this, while (b) and (c) represent actual dispersed amounts, the figure in (a) is the amount of perchlorate produced and only a fraction (f) of it has been dispersed and often in a more localized fashion. In addition, dispersal of (b) has taken place only over agricultural land. Considering that the total land area in the United States is 5.5 x the arable land area, in terms of incorporation into the food chain,the figure cited in (b) has a proportionately greater impact. Most estimates of fwill thus suggest that over the considered period, the contribution of CNF to incorporation of perchlorate in the food chain has likely been comparable to oxidizer perchlorate, with natural production being a lesser source. Fireworks presently constitute a potentially important source of increasing importance but a quantitative impact cannotyet be assessed.

Sample processing method for the determination of perchlorate in milk.

In recent years, many different water sources and foods have been reported to contain perchlorate. Studies indicate that significant levels of perchlorate are present in both human and dairy milk. The determination of perchlorate in milk is particularly important due to its potential health impact on infants and children. As for many other biological samples, sample preparation is more time consuming than the analysis itself. The concurrent presence of large amounts of fats, proteins, carbohydrates, etc., demands some initial cleanup; otherwise the separation column lifetime and the limit of detection are both greatly compromised. Reported milk processing methods require the addition of chemicals such as ethanol, acetic acid or acetonitrile. Reagent addition is undesirable in trace analysis. We report here an essentially reagent-free sample preparation method for the determination of perchlorate in milk. Milk samples are spiked with isotopically labeled perchlorate and centrifuged to remove lipids. The resulting liquid is placed in a disposable centrifugal ultrafilter device with a molecular weight cutoff of 10 kDa, and centrifuged. Approximately 5-10 ml of clear liquid, ready for analysis, is obtained from a 20 ml milk sample. Both bovine and human milk samples have been successfully processed and analyzed by ion chromatography-mass spectrometry (IC-MS). Standard addition experiments show good recoveries. The repeatability of the analytical result for the same sample in multiple sample cleanup runs ranged from 3 to 6% R.S.D. This processing technique has also been successfully applied for the determination of iodide and thiocyanate in milk.