The absence of well-validated biomarkers of manganese (Mn) exposure in children remains a major obstacle for studies of Mn toxicity. We developed a hair cleaning methodology to establish the utility of hair as an exposure biomarker for Mn and other metals (Pb, Cr, Cu), using ICP-MS, scanning electron microscopy, and laser ablation ICP-MS to evaluate cleaning efficacy. Exogenous metal contamination on hair that was untreated or intentionally contaminated with dust or Mn-contaminated water was effectively removed using a cleaning method of 0.5% Triton X-100 sonication plus 1N nitric acid sonication. This cleaning method was then used on hair samples from children (n=121) in an ongoing study of environmental Mn exposure and related health effects. Mean hair Mn levels were 0.121 μg/g (median = 0.073 μg/g, range = 0.011 – 0.736 μg/g), which are ~4 to 70-fold lower than levels reported in other pediatric Mn studies. Hair Mn levels were also significantly higher in children living in the vicinity of active, but not historic, ferroalloy plant emissions compared to controls (P<0.001). These data show that exogenous metal contamination on hair can be effectively cleaned of exogenous metal contamination, and they substantiate the use of hair Mn levels as a biomarker of environmental Mn exposure in children.

Native oxide surfaces of stainless steel 316L and Nitinol alloys and their constituent metal oxides namely, nickel, chromium, molybdenum, manganese, iron and titanium were modified with long chain organic acids to better understand organic film formation. The adhesion and stability of films of octadecylphosphonic acid, octadecylhydroxamic acid, octadecylcarboxylic acid and octadecylsulfonic acid on these substrates was examined in this study. The films formed on these surfaces were analyzed by diffuse reflectance infrared Fourier transform spectroscopy, contact angle goniometry, atomic force microscopy and matrix assisted laser desorption ionization mass spectrometry. The effect of the acidity of the organic moiety and substrate composition on the film characteristics and stability is discussed. Interestingly, on the alloy surfaces, the presence of less reactive metal sites does not inhibit film formation.

Regioselective labelling of arene rings via electrophilic exchange is often dictated by the electronic environment caused by substituents present on the aromatic system. Previously, we observed the presence of a t‐butyl group, either covalently bond or added as an external reagent, could impart deuterium exchange to the unactivated, C1‐position of estrone. Here, we provide nuclear magnetic resonance analysis of this exchange in a solvent system composed of 50:50 trifluoroacetic acid and D2O with either 2‐t‐butylestrone or estrone in the presence of t‐butyl alcohol has shed insights into the mechanism of this t‐butyl‐catalyzed exchange. Fast exchange of the t‐butyl group concurrent with the gradual reduction of the H1 proton signal in both systems suggest a mechanism involving ipso attack of the t‐butyl position by deuterium. The reversible addition/elimination of the t‐butyl group activates the H1 proton towards exchange by a mechanism of t‐butyl incorporation, H1 activation and exchange, followed by eventual t‐butyl elimination. Density functional calculations are consistent with the observation of fast t‐butyl exchange concurrent with slower H1 exchange. The σ‐complex resulting from ipso attack of deuterium at the t‐butyl carbon was 6.6 kcal/mol lower in energy than that of the σ‐complex resulting from deuterium attack at C1. A better understanding of the t‐butyl‐catalyzed exchange could help in the design of labelling recipes for other phenolic metabolites.

Rationale:The absence of well-validated biomarkers of manganese (Mn) exposure in children remains an obstacle for human studies of Mn toxicity. Approach:A cross-sectional epidemiological study of environmental Mn neurotoxicity in children living in the vicinity of ferroalloy plant activity is underway in Italy. Mn exposure is characterized via 24hr personal air samplers, Mn in soil, settled dust, tap water, and dietary Mn intake using FFQ. Candidate biomarkers collected concurrent with environmental measures include blood, urine, hair, fingernails, and saliva (teeth analyses will be reported separately by Arora). Because of the susceptibility of hair to Mn contamination, cleaning/processing methodologies to minimize contamination risk were developed. A sub-set of subjects (n~120) were used to investigate the relationship(s) between exposure and resultant candidate biomarker Mn levels. Results:The three study regions of active ferroalloy activity (Bagnolo Mella), past ferroalloy activity (Valcamonica), and the reference region (Garda Lake) exhibited significantly different levels of soil and airborne Mn levels consistent with current or past ferroalloy emissions. Blood Mn levels were not associated with exposure region. In contrast, hair Mn levels were elevated in children from Bagnollo Mella compared to the Garda Lake reference group; hair levels in children from the Valcamonica region were intermediate. Associations of all candidate biomarkers with environmental exposure measures will be presented and discussed.Conclusion: These data suggest that hair Mn correlates with environmental Mn exposure in children, while blood and urine Mn do not. Furthermore, rigorous cleaning of hair is sufficient to remove external Mn contamination from dust.