Thiocyanate Levels Research Articles

Urinary heavy metals, phthalates, phenols, thiocyanate, parabens, pesticides, polyaromatic hydrocarbons but not arsenic or polyfluorinated compounds are associated with adult oral health: USA NHANES, 2011-2012.

Links between environmental chemicals and human health have emerged over the last few decades, but the effects on oral health have been less studied. Therefore, it was aimed to study the relationships of different sets of urinary chemical concentrations and adult oral health conditions in a national and population-based setting. Data was retrieved from the United States National Health and Nutrition Examination Surveys, 2011-2012 including demographics, self-reported oral health conditions and urinary environmental chemical concentrations (one third representative sample of the study population). Chi-square test, t test, and survey-weighted logistic and multi-nominal regression modeling were performed. Of 4566 American adults aged 30-80, 541 adults (11.9 %) reported poor teeth health while 1020 adults (22.4 %) reported fair teeth. Eight hundred fifty-five people (19.1 %) claimed to have gum disease, presented with higher levels of urinary cadmium, cobalt and polyaromatic hydrocarbons. Six hundred three adults (13.3 %) had bone loss around the mouth, presented with higher levels of cadmium, nitrate, thiocyanate, propyl paraben and polyaromatic hydrocarbons. Eight hundred forty-five adults (18.5 %) had tooth loose not due to injury, presented with higher level of cadmium, thiocyanate and polyaromatic hydrocarbons. Eight hundred forty-five adults (18.5 %) with higher levels of lead, uranium, polyaromatic hydrocarbons but lower level of triclosan noticed their teeth did not look right. Three hundred fifty-one adults (7.7 %) often had aching in the mouth and 650 (14.3 %) had it occasionally, presented with higher levels of phthalates, pesticides and polyaromatic hydrocarbons. Benzophenone-3 and triclosan elicited protective effects. Regulation of environmental chemicals in prevention of adult oral health might need to be considered in future health and environmental policies.

Comparative reactivity of the myeloperoxidase-derived oxidants HOCl and HOSCN with low-density lipoprotein (LDL): Implications for foam cell formation in atherosclerosis

Atherosclerosis is characterised by the accumulation of lipids within macrophages in the artery wall. Low-density lipoprotein (LDL) is the source of this lipid, owing to the uptake of oxidised LDL by scavenger receptors. Myeloperoxidase (MPO) released by leukocytes during inflammation produces oxidants that are implicated in atherosclerosis. Modification of LDL by the MPO oxidant hypochlorous acid (HOCl), results in extensive lipid accumulation by macrophages. However, the reactivity of the other major MPO oxidant, hypothiocyanous acid (HOSCN) with LDL is poorly characterised, which is significant given that thiocyanate is the favoured substrate for MPO. In this study, we comprehensively compare the reactivity of HOCl and HOSCN with LDL, and show key differences in the profile of oxidative damage observed. HOSCN selectively modifies Cys residues on apolipoprotein B100, and oxidises cholesteryl esters resulting in formation of lipid hydroperoxides, 9-hydroxy-10,12-octadecadienoic acid (9-HODE) and F2-isoprostanes. The modification of LDL by HOSCN results macrophage lipid accumulation, though generally to a lesser extent than HOCl-modified LDL. This suggests that a change in the ratio of HOSCN:HOCl formation by MPO from variations in plasma thiocyanate levels, will influence the nature of LDL oxidation in vivo, and has implications for the progression of atherosclerosis.

Lower serum levels of selenium, copper, and zinc are related to neuromotor impairments in children with konzo

We assessed the relationship between key trace elements and neurocognitive and motor impairments observed in konzo, a motor neuron disease associated with cassava cyanogenic exposure in nutritionally challenged African children. Serum concentrations of iron, copper, zinc, selenium, and neurotoxic lead, mercury, manganese, cadmium, and cobalt were measured in 123 konzo children (mean age 8.53years) and 87 non-konzo children (mean age 9.07years) using inductively coupled plasma mass spectrometry (ICPMS). Concentrations of trace elements were compared and related to performance scores on the Kaufman Assessment Battery for Children, 2nd edition (KABC-II) for cognition and Bruininks–Oseretsky Test, 2nd edition (BOT-2) for motor proficiency. Children with konzo had low levels of selenium, copper, and zinc relative to controls. Selenium concentration significantly correlated with serum 8,12-iso-iPF2α-VI isoprostane (Spearman r=0.75, p<0.01) and BOT-2 scores (r=0.31, p=0.00) in children with konzo. Elemental deficiency was not associated with poor cognition. Mean (SD) urinary level of thiocyanate was 388.03 (221.75) μmol/l in non-konzo compared to 518.59 (354.19) μmol/l in konzo children (p<0.01). Motor deficits associated with konzo may possibly be driven by the combined effects of cyanide toxicity and Se deficiency on prooxidant mechanisms. Strategies to prevent konzo may include dietary supplementation with trace elements, preferentially, those with antioxidant and cyanide-scavenging properties.

Konzo prevention in six villages in the DRC and the dependence of konzo prevalence on cyanide intake and malnutrition

Six villages in Boko Health Zone, Bandundu Province, DRC, were studied with 4588 people, 144 konzo cases and konzo prevalences of 2.0–5.2%. Konzo incidence is increasing rapidly in this area. Food consumption scores were obtained from the households with konzo and the mean % malnutrition calculated for each village. Urine samples were obtained from 50 school children from each village and % high urinary thiocyanate content (>350μmol/L) determined. The experimental data relating % konzo prevalence (%K) to % children with high urinary thiocyanate content (%T) and % malnutrition (%M) for the six villages were fitted to an equation %K=0.06%T+0.035%M. This confirms that konzo is due to a combination of high cyanide intake and malnutrition. The village women used the wetting method to remove cyanogens from cassava flour. During the 9-month intervention there were no new cases of konzo; cyanide in flour had reduced to WHO safe levels and mean urinary thiocyanate levels were greatly reduced. To prevent konzo at least 60–70% of women should use the wetting method regularly. The wetting method is now accepted by the World Bank, FAO and WHO as a sensitive intervention. Four successful konzo interventions have involved nearly 10,000 people in 13 villages, the cost is now $16 per person and the methodology is well established.

Salivary Thiocyanate, Uric Acid and pH as Biomarkers of Periodontal Disease in Tobacco Users and Non-Users- An In-Vitro Study.

Biomarkers of tobacco exposure are used to confirm the absorption of specific smoke constituents in a quantitative manner. Periodontal status was measured by Community periodontal Index (WHO). Salivary thiocyanate was determined using spectrophotometric analysis, Salivary uric acid concentration was determined using the enzymatic uric acid assay reagent. pH was measured using pH strips. Proportion of participants with periodontal pockets of 4-5mm was highest among tobacco smokers (80.0%) and periodontal pockets of 6mm or more were observed to be higher among tobacco chewers (26.67%). When LOA scores among tobacco chewers were recorded 26.7% of them presented with attachment loss of 0-3mm. 46.7% of them were affected with loss of attachment of 4-5mm and loss of attachment 6-8mm was found in 16.7%. 6.7% of them were found to be having loss of attachment of 9-11mm. 3.3% of them were found to be having loss of attachment of 12mm or more. The LOA scores in non- tobacco users showed 46.7% of 0-3mm, 50.0% of 4-5mm and 3.33% of 6-8mm attachment loss. The mean level of thiocyanate level detected in saliva of tobacco smokers was 172 ± 54.7 μg/ml and 203.70± 45.7 μg/ml in tobacco chewers. The mean uric acid levels was found to be 2.54 ±0.63 (μg/dl) in smokers and 2.65 ± 0.37(μg/dl) in chewers and in non tobacco users it was 2.33 ± 0.47 μg/dl. Tobacco users had significantly higher concentration of SCN levels than non-users.

Effect of oxytocin on enzyme activities in bovine milk

The objective of this study was to determine the effect of administration of oxytocin prior to milking on enzyme activities and thiocyanate concentration in bovine milk. Intramuscular administration of oxytocin (20 IU) was made to a group of cattle comprising 8 animals, whilst a second group was kept as control. Significant (p < 0.01) differences were measured in enzymatic levels of oxytocin-treated and control bovine milk. Alkaline phosphatase and lipase activity were reduced in milk of oxytocin-treated cows. However, the trend was the opposite for acid phosphatase, where high enzyme activity was observed in milk after oxytocin treatment (0.010 U mL−1) compared with the control (0.004 U mL−1). Treating cattle with oxytocin did not significantly (p < 0.01) affect lactoperoxidase concentration but increased thiocyanate levels of milk by ∼6.5%. In conclusion, oxytocin administration to cows cause variations in milk enzyme activities and might consequently affect milk stability against certain deteriorative changes.

High plasma thiocyanate levels are associated with enhanced myeloperoxidase-induced thiol oxidation and long-term survival in subjects following a first myocardial infarction

Elevated levels of myeloperoxidase (MPO) are associated with poor cardiovascular outcomes. MPO uses H2O2 to generate oxidants including HOCl and HOSCN, from chloride and thiocyanate (SCN−) ions, respectively. SCN− is the preferred substrate. Elevation of this anion decreases HOCl generation and increases HOSCN formation, a thiol-specific oxidant. Such changes are of potential relevance to people with elevated SCN− levels, such as smokers. In this retrospective study, we examined whether elevated plasma MPO and SCN− levels increased thiol oxidation as a result of increased HOSCN formation, and impacted on long-term survival in 176 subjects (74 non-smokers, 46 smokers, and 56 previous smokers) hospitalized after a first myocardial infarction. Plasma thiols were not significantly altered in smokers compared to non-smokers or past smokers. However, significant positive correlations were detected between SCN− levels and MPO-induced thiol loss in the total population (r = 0.19, P = 0.020) and smokers alone (r = 0.58, P < 0.0001). Twelve-year all-cause mortality data indicate that above median MPO is significantly associated with higher mortality, but below-median MPO and above-median SCN− results in increased survival, compared to below-median SCN−. Cox proportional hazard analysis showed a significant decrease in mortality for each 1 μM increase in SCN− (0.991; P = 0.040). Subject age was, as expected, a strong predictor of subject survival. Overall these data suggest that subjects with below-median MPO and above-median SCN− have better long-term survival, and that elevated plasma levels of SCN− might be protective in at least some populations.

SOME HEALTH EFFECTS DUE TO CHRONIC OCCUPATIONAL EXPOSURE TO CYANIDE

Introduction: Exposure to cyanide is encountered in many industries as in Case Hardening and Electroplating. Chronic exposure to cyanide is associated with some health effects including its effect on thyroid gland. Aim of work: To study the health effects due to chronic occupational exposure to cyanide with special emphasis on the thyroid gland. Materials and Methods: This study was conducted on 56 workers exposed to cyanide in case hardening and electroplating industry. Their age ranged between 36 and 59 years with a mean of 46.96 ± 5.51 years. They are exposed to cyanide from 4 to 31 years with a mean of 19.86 ± 8.53 years. They were compared with 60 workers not exposed to cyanide as a control group, Their age ranged between (30-60) years with a mean of 45.76 and S.D. ±11.81. Hydrogen cyanide was measured in air of workplace environment. Serum thiocyanate serum and thyroid hormones (T3, T4, and TSH) were measured. Results: The serum thiocyanate levels showed highly statistically significant difference among exposed workers when compared to the control. A highly statistically significant lower serum levels of T3 and T4 among the exposed group, and higher serum levels of TSH compared to the control group. Serum TSH showed a statistically significant positive correlation with serum thiocyante among the exposed workers, a statistically significant negative correlation as regards T3, and a negative correlation between TSH and T4 but it is not statistically significant. Conclusion: Cyanide exposure is associated with decrease in thyroid functions but not clinically detected.

English

There were 68 konzo cases in three villages in Boko Health Zone, Bandundu Province, Democratic Republic of Congo (DRC), where yearly incidence had increased greatly since 2009. The nine months long intervention to prevent konzo started in the wet season. Village women were taught the wetting method, after which there were no new konzo cases and urinary thiocyanate levels were low. Using data from four different interventions in March 2010, July 2011, September 2013 and the present intervention in October-November 2012, a correlation was found between the monthly cyanide intake (measured by percentage of children with high urinary thiocyanate level) and the monthly konzo incidence. This dose response relationship between cyanide intake and konzo incidence, together with the prevention of konzo in many villages using the wetting method to reduce cyanogen intake, shows that konzo is very likely to be due to high cyanide/low sulfur amino acid intake in a diet of bitter cassava. Key words: Dose-response relation, konzo prevalence, urinary thiocyanate, cyanide, cassava flour, wetting method.

Occurrence of Perchlorate and Thiocyanate in Human Serum From E-Waste Recycling and Reference Sites in Vietnam: Association With Thyroid Hormone and Iodide Levels

Perchlorate (ClO4 (-)) and thiocyanate (SCN(-))interfere with iodide (I(-)) uptake by the sodium/iodide symporter, and thereby these anions may affect the production of thyroid hormones (THs) in the thyroid gland. Although human exposure to perchlorate and thiocyanate has been studied in the United States and Europe, few investigations have been performed in Asian countries. In this study, we determined concentrations of perchlorate, thiocyanate, and iodide in 131 serum samples collected from 2 locations in Northern Vietnam, Bui Dau (BD; electrical and electronic waste [e-waste] recycling site) and Doung Quang (DQ; rural site) and examined the association between serum levels of these anions with levels of THs. The median concentrations of perchlorate, thiocyanate, and iodide detected in the serum of Vietnamese subjects were 0.104, 2020, and 3.11ngmL(-1), respectively. Perchlorate levels were significantly greater in serum of the BD population (median 0.116ngmL(-1)) than those in the DQ population (median 0.086ngmL(-1)), which indicated greater exposure from e-waste recycling operations by the former. Serum concentrations of thiocyanate were not significantly different between the BD and DQ populations, but increased levels of this anion were observed among smokers. Iodide was a significant positive predictor of serum levels of FT3 and TT3 and a significant negative predictor of thyroid-stimulating hormone in males. When the association between serum levels of perchlorate or thiocyanate and THs was assessed using a stepwise multiple linear regression model, no significant correlations were found. In addition to greater concentrations of perchlorate detected in the e-waste recycling population, however, given that lower concentrations of iodide were observed in the serum of Vietnamese females, detailed risk assessments on TH homeostasis for females inhabiting e-waste recycling sites, especially for pregnant women and their neonates, are required.

Time-dependent comparative evaluation of some important biomarkers of acute cyanide poisoning in rats: an aid in diagnosis

Objective: The study focuses on time-dependent comparative evaluation of various biomarkers of acute cyanide poisoning in rats.Methods: Blood gas (analyzer), lactate, pyruvate, cyanide, thiocyanate (spectrophotometer) and 2-amino-2-thiazoline-4-carboxylic acid (ATCA; gas chromatography–mass spectrometry) in plasma or urine, and various physiological parameters (polygraph) were measured.Results: Cyanide poisoning was characterized by elevated lactate, cyanide, thiocyanate and ATCA concentrations in plasma up to 15 min, 4, 16 and 24 h, respectively, while high urinary thiocyanate and ATCA levels were measured between 4 and 24 h.Conclusion: ATCA concentration in plasma and urine was found to be more reliable indicator of cyanide poisoning.

Biochemical, oxidative and histological changes caused by sub-acute oral exposure of some synthetic cyanogens in rats: Ameliorative effect of α-ketoglutarate

Time-dependent cyanide generation and acute toxicity of six different cyanogens were reported earlier, out of which malononitrile (MCN), propionitrile (PCN), and sodium nitroprusside (SNP) were found to be very toxic. We report here 14d sub-acute toxicity of MCN, PCN, and SNP (oral; 1/10 LD50 daily) in female rats, and its amelioration by α-ketoglutarate (α-KG; oral; 5.26mmol/kg; +5min), a potential cyanide antidote. Significant decrease in white blood cells (PCN, SNP), platelets count (PCN), and blood glucose levels (MCN, PCN, SNP) was accompanied by elevated levels of alanine aminotransferase, lactate dehydrogenase (MCN, PCN, SNP), and aspartate aminotransferase (PCN, SNP). Oxidative damage was evidenced by diminished total antioxidant status in plasma and enhanced malondialdehyde levels in liver and kidney. This was accompanied by diminished levels of reduced glutathione, glutathione peroxidase, glutathione reductase, superoxide dismutase, and catalase in the brain, liver and kidney. We also observed increased levels of blood cyanide and thiocyanate, together with inhibition of cytochrome c oxidase and thiosulfate-sulfur transferase activities in total brain and liver homogenate, respectively. Cyanogens also produced several histological changes in all the organs studied. Post-treatment with α-KG significantly abrogated the toxicity of cyanogens, indicating its utility as an antidote for long-term cyanogen exposure.

Iodine Status in Turkish Populations and Exposure to Iodide Uptake Inhibitors

Perchlorate, nitrate, and thiocyanate are competitive inhibitors of the sodium iodide symporter of the thyroid membrane. These inhibitors can decrease iodine uptake by the symporter into the thyroid gland and may disrupt thyroid function. This study assesses iodine status and exposure to iodide uptake inhibitors of non-pregnant and non-lactating adult women living in three different cities in Turkey (Istanbul, Isparta and Kayseri). We measured iodine and iodide uptake inhibitors in 24-hr urines collected from study participants (N = 255). All three study populations were mildly iodine deficient, with median urinary iodine (UI) levels of 77.5 µg/L in Istanbul, 58.8 µg/L in Isparta, and 69.8 µg/L in Kayseri. Perchlorate doses were higher in the study population (median 0.13 µg/kg/day), compared with a reference population (median 0.059 µg/kg/day), but lower than the U.S. EPA reference dose (0.7 µg/kg/day). Urinary thiocyanate levels increased with increasing exposure to tobacco smoke, with non-smokers (268 µg/L) significantly lower than light smokers (1110 µg/L), who were significantly lower than heavy smokers (2410 µg/L). This pilot study provides novel data indicating that study participants were moderately iodine deficient and had higher intakes of the iodide uptake inhibitor perchlorate compared with a reference population. Further investigation is needed to characterize the thyroid impact resulting from iodine deficiency coupled with exposure to iodide uptake inhibitors such as perchlorate, thiocyanate and nitrate.

Estimation and correlation of salivary thiocyanate levels in healthy and different forms of tobacco users having chronic periodontitis: A cross-sectional biochemical study.

Background:Periodontitis is a common inflammatory disease with complex and multi-factorial origin. Tobacco usage has shown its adverse effect on periodontal health. Various components within saliva not only protect the integrity of oral tissues, but also provide clues to local and systemic diseases and conditions. Salivary thiocyanate (SCN) has been shown to be a chemical indicator in smokers and smokeless tobacco users. Noninvasive nature of salivary testing has made it an attractive and effective alternative to blood and urine testing. Limited studies are there comparing and correlating the salivary SCN levels in smokers with chronic periodontitis (CP). However, no studies show correlation of salivary SCN among gutka chewers with CP.Aims and Objectives:The objective of the following study is to estimate, compare, and correlate the SCN levels in periodontally healthy, CP, smokers with CP and gutka chewers with CP subjects.Materials and Methods:Study includes 120 subjects with age 18-55 years, categorized as periodonally healthy (n = 30), CP (n = 30), smokers (n = 30), and gutka chewers (n = 30) with CP. Required clinical parameters such as gingival index, probing depth and clinical attachment loss were recorded and salivary SCN levels were estimated through ultraviolet-spectrophotometer.Results:Mean salivary SCN level were shown to be higher among smokers and gutka chewers with CP as compared to healthy and CP alone.Conclusion:The present study exhibited the significant increase in salivary SCN levels among smokers and gutka chewers when compared to others, concluding that the analysis of salivary SCN levels could be used as an adjunctive means of diagnosis.

Qualitative test for the detection of extraneous thiocyanate in milk.

Thiocyanate is one of the three components of lactoperoxidase system for preserving the milk under the conditions where chilling facilities do not exist due to economic and technical reasons. In 1988, International Dairy Federation (IDF) has recommended the levels and the code of practices for the application of LP-system. As the excessive use of thiocyanates beyond the recommended limits can lead to human health hazards, its rapid detection in milk at the reception dock of dairy, where milk is tested for quality before its acceptance or rejection, is necessary. For simple and rapid detection of added thiocyanates in milk, two types of qualitative tests have been developed in this study, of which one is applicable directly to milk and the other is applicable to TCA filtrate of milk. The results of the test reveal that as low as 0.6ppm of added thiocyanate (equivalent to 1ppm of potassium thiocyanate) can be detected. The orange to orange-red color obtained in the test solution can be considered the basis of rejecting milk assuming that it has added levels of thiocyanate.

Thiocyanate as a Biomarker for Cyanide Exposure in the U.S. Population

Background: Tobacco smoke exposure is one of the major causes of lung cancer, respiratory infection, and heart disease. Cyanide, one of many toxic chemicals present in tobacco smoke, is considered the major contributor to the cardiovascular toxicity of tobacco smoke. Good biomarkers to reliably measure cyanide exposure are therefore critical. Urinary levels of thiocyanate, the main metabolic product of cyanide, can be used to assess cyanide exposure. Aims: To evaluate human exposure to cyanide by measuring urinary concentrations of its metabolite, thiocyanate. Method: We measured urinary thiocyanate levels in samples from U.S. residents, ages 6 years and older, during 2001 – 2012 as part of the National Health and Nutrition Examination Survey (NHANES) using ion chromatography-tandem mass spectrometry. Results: When geometric means of urinary thiocyanate levels were adjusted for age, fasting, sex, smoking status and race-ethnicity, significantly higher levels of urinary thiocyanate were detected in smokers compared with non-smokers. Conclusion: These data provide an updated population-based assessment of the magnitude and prevalence of cyanide exposure in the U.S. population. Differences in urinary thiocyanate levels between smokers and non-smokers indicate cyanide exposure is largely driven by exposure to tobacco smoke.

Urinary Perchlorate and Thiocyanate Concentrations in Pregnant Women from Toronto, Canada

Dear Editor: The developing fetus is dependent upon maternal iodine for thyroid hormone production required for normal neurodevelopment. Perchlorate is ubiquitous at low levels in the environment from the manufacture of air bags and solid rocket fuel and is present in a wide variety of foodstuffs, a component of some crop fertilizers used in the United States, and a byproduct of fireworks displays. Low-level perchlorate exposure has been recently suggested to adversely affect thyroid function. Perchlorate acts as a competitive inhibitor of the sodium/iodide symporter and is also actively transported by the sodium/iodide symporter to be concentrated into the thyroid follicular cells. Thiocyanate, from cigarette smoke and some Brassica genus vegetables in the diet, is a weaker inhibitor of sodium/iodide symporter. Environmental perchlorate and thiocyanate exposures during pregnancy could potentially decrease thyroidal iodine uptake in the mother and/or her fetus and thus decrease thyroid hormone synthesis. The objective of this study was to assess the status of low-level environmental urinary perchlorate and thiocyanate exposures in a cohort of pregnant women in Toronto, Canada. We recruited pregnant women presenting for routine care from among four low-risk outpatient obstetric clinics between December 2009 to February 2011 at Mount Sinai Hospital, Toronto, Canada. Women with a history of thyroid disease were excluded. Women completed a questionnaire to provide information regarding their age, gestational age, race/ethnicity, country of origin, highest level of education, income level, cigarette smoking status, and use of prenatal and/or multivitamins before and during pregnancy. Women also completed a food frequency questionnaire to provide information on their dietary iodine intake, including use of iodized salt. Subjects provided a single-spot urine sample, from which perchlorate and thiocyanate concentrations were measured using ion chromatography–mass spectrometry (1). The Mount Sinai Hospital Ethics Board approved the protocol. Our study cohort consisted of 150 women (mean age 33.8±4.4 years) in their second and third trimesters (mean gestational age 29±7.9 weeks) who were primarily Caucasian (73%), well educated (96% more than a high school education), and relatively affluent (64% with median annual income >$100,000). The median urinary perchlorate concentration was 3.2 μg/L (range 0.5–48.1 μg/L), and the median urinary thiocyanate concentration was 351 μg/L (range 28–1195 μg/L). These pregnant women were iodine sufficient (median urinary iodine concentration 227.1 μg/L) (2). This is the first report describing population urinary perchlorate and thiocyanate concentrations in Canada. In 2005, Backus and colleagues (3) had reported perchlorate levels ranging from nondetectable to 0.33 μg/L in water samples from 55 Canadian areas, including sites of heavy industry, urbanization, agriculture, atmospheric deposition, and recent fireworks displays. The potential effects of perchlorate exposure on human health remain controversial, and its monitoring and cleanup would carry significant financial costs. Currently, Health Canada (4) continues to monitor perchlorate levels in drinking water, in which a recommended threshold of <6 μg/L is in place, but not enforced. There are no regulations for thiocyanate currently in place. There are currently no normative ranges for urinary perchlorate and thiocyanate concentrations. However, the low levels of both perchlorate and thiocyanate in the present study are comparable to those previously reported in iodine-deficient and iodine-sufficient pregnant women from Wales (5), Italy (5), Argentina (6), Greece (7), and the United States (6). There was no association between urinary perchlorate levels and maternal thyroid function in these previous studies, in contrast to a decrease in serum thyroxine concentrations in women with urinary iodine levels <100 μg/L from the U.S. National Health and Nutrition Examination Survey (8). The limitations of our study included the use of a convenience sample in our subject selection, the potential nongeneralizability of the findings to other regions, and the absence of serum thyroid function tests. The results of the present study suggest that the low urinary perchlorate concentrations in Canada would be unlikely to alter the thyroid function of pregnant women or their fetuses, especially in iodine-sufficient regions, although further studies are warranted to better explore these relationships.

Control of konzo by detoxification of cassava flour in three villages in the Democratic Republic of Congo

Three villages in Boko Health Zone, Bandundu Province, Democratic Republic of Congo (DRC), had 61 konzo cases and konzo prevalences of 2.5%, 4.1% and 7.5% respectively. Konzo cases occurred every year for 10 years and every month, peaking in July. The high mean cyanide content of cassava flour of 50 ppm was due to short soaking of cassava roots for 1-2 days instead of 3-4 days. Konzo cases were examined and village women taught the wetting method that removes cyanogens from flour. The villages were visited every month for 1 year following previous methodology. No new konzo cases occurred during the intervention, mean flour cyanide levels reduced from 50 to 14 ppm and mean urinary thiocyanate levels of school children reduced from 930 to 150 μmole/L. The percentage of children with urinary thiocyanate levels of >350 μmole/L was reduced from a maximum of 80 in Ikialala before the intervention to 0 in Ikusama, Ikialala and 3 in Imboso Mwanga 1 year later. This is the second time that konzo has been controlled and success depends on regular use of the wetting method by village women. The methodology is now being used in other villages in DRC with financial support of AusAID.

Acute toxicity of some synthetic cyanogens in rats: Time-dependent cyanide generation and cytochrome oxidase inhibition in soft tissues after sub-lethal oral intoxication

Cyanogens include complex nitrile-containing compounds that can generate free cyanide of toxicological significance. Acute toxicity, time-dependent cyanide generation and cytochrome oxidase (CYTOX) inhibition in soft tissues, and urinary thiocyanate levels were measured after acute cyanogen intoxication in rats. Order of cyanogens in terms of LD₅₀ was: malononitrile (MCN)>propionitrile (PCN)≈sodium nitroprusside (SNP)>acrylonitrile (ACN)>succinonitrile (SCN)>acetonitrile (ATCN) for oral, and SNP>MCN>ACN>PCN>SCN>ATCN for intraperitoneal and subcutaneous routes. MCN was most toxic by oral (LD₅₀=66.4 mg/kg) and SNP by intraperitoneal (LD₅₀=16.7 mg/kg) and subcutaneous (LD₅₀=11.9 mg/kg) routes. Minimum survival time (25 min) was recorded after 4.0 LD₅₀ ATCN. Order of cyanogens (0.75 LD₅₀; oral) on the basis of maximum blood cyanide and time of peak cyanide generation were: ATCN>SNP>SCN>PCN>MCN>ACN, and MCN (30 min)<SNP (1h)<PCN≈ACN (8h)<SCN (24h)<ATCN (72 h), respectively. In most cases, time profile of cyanide generation correlated with corresponding CYTOX inhibition and urinary thiocyanate levels. With the understanding of time-dependent toxicity of different cyanogens, suitable therapeutic windows can be designed for their management.

Impact of recycling cyanide and its reaction products on upstream unit operations

A typical operations outcome to dealing with the environmental and economic issues associated with cyanide in gold plant tailings streams involves the recycle of cyanide and its associated reaction products. This recycle stream may take the form of return dam water or tailings thickener overflow to the mill, or a cyanide recovery stream to the leach from a SART (sulphidization–acidification–recycling–thickening) or AVR (acidification–volatilization–reneutralization) circuit. The chemical composition and cyanide speciation of these solutions may be relatively complex, containing various metal cyanide species, thiocyanate, cyanate and other breakdown products.Several of these species are reported to have a deleterious effect on upstream unit operations. For example, while cyanide is in common use as a depressant for pyrite in mineral flotation, ferrocyanide and thiocyanate ions have also been shown to exhibit a depressant action in some cases. Primary flotation recovery of gold can thus be compromised and may be responsible for significant lost revenue, particularly from high-grade refractory gold operations. Bioleaching plants tend to separate cyanide circuits to an independent water balance to ensure that no cyanide or thiocyanate returns to inflict dire consequences on the bacterial population. Tolerable levels of these ions are exceedingly low, creating a risk factor and constraining water balance flexibility. Milling-in-cyanide has been periodically mooted as a beneficial circuit modification, particularly in operations that have tailings thickening, SART or dolomitic ore from which significant levels of free and complexed cyanides and thiocyanates are present. Potential consequences include unwanted side reactions with freshly activated mineral surfaces within mills operating at elevated temperatures and significant cyanide losses under these conditions.The evidence for the effects of recycled cyanides and associated species on upstream gold processing circuits have to date not been assessed in a systematic fashion. This paper presents a review of the available literature and analysis of associated data in these areas. Common arguments from operators justifying certain process plant configurations, modifications and operating setpoints around recycle streams are examined. Impacts of cyanide recycle on milling, flotation and bioleaching are quantified in the context of exemplary case studies. The various literature and case study flowsheets provide a useful analysis of the application of recycle streams to operating plant flowsheets, often requiring creative or inelegant solutions. In the current work, plant operating data is analyzed to quantify some of these effects; moreover, a simulation model has been developed to further quantify and explain some of these effects and provide insight into the decision-making process for plant designers and operators alike. Recycles without water treatment or other means may raise thiocyanate and cyanide levels above site-specific tolerances for operability.