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Daily dietary-boron intake and on-the-job inspired boron were compared with blood- and urine-boron concentrations in workers engaged in packaging and shipping borax. Fourteen workers handling borax at jobs of low, medium, and high dust exposures were sampled throughout full shifts for 5 consecutive days each. Airborne borax concentrations ranged from means of 3.3 mg/m3 to 18 mg/m3, measured gravimetrically. End-of-shift mean blood-boron concentrations ranged from 0.11 to 0.26 microgram/g; end-of-shift mean urine concentrations ranged from 3.16 to 10.72 micrograms/mg creatinine. Creatinine measures were used to adjust for differences in urine-specific gravity such that 1 ml of urine contains approximately 1 mg creatinine. There was no progressive increase in end-of-shift blood- or urine-boron concentrations across the days of the week. Urine testing done at the end of the work shift gave a somewhat better estimate of borate exposure than did blood testing, was sampled more easily, and was analytically less difficult to perform. Personal air samplers of two types were used: one, the 37-mm closed-face, two-piece cassette to estimate total dust and the other, the Institute of Occupational Medicine (IOM) sampler to estimate inspirable particulate mass. Under the conditions of this study, the IOM air sampler more nearly estimated human exposure as measured by blood- and urine-boron levels than did the sampler that measured total dust.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental evidence now supports the nutritional essentiality of boron (B) in some biological systems, and accordingly, the need for reliable analytical B data is increasing. However, the accurate determination of B in biological materials is a formidable challenge at low concentrations (<1 mg B/kg). Recent studies still show significant analytical discrepancies in the analysis of animal tissues and fluids, despite the development of instrumental techniques such as TIMS, ICP-MS, ICP-ES, ICAP, SIMS, NA-MS, PGAA, NRA, and so forth, which have demonstrated detection limits approaching or exceeding (microg B/kg concentrations. Since boric acid is both volatile and ubiquitous in nature, the chemical and physical pathways for B contamination and its loss are manifold, especially during sample preparation. An added obstacle is the inadequacy of biological reference materials certified for B below mg B/kg. With an emphasis toward sample preparation and ICP-MS analysis, examples are provided in this article to help the analyst avoid common problems associated with the analysis of B from biological sources. Topics that are discussed include contamination from Teflon vessels during microwave digestion, losses owing to freeze-drying, B isotopic variations, standards preparation, reagent backgrounds, and instrumental interferences.

Timed-mated Sprague-Dawley rats (60/group) were exposed to boric acid (BA) from gestational days (gd) 0 to 20. BA added to the diet (0, 0.025, 0.050, 0.075, 0.1, or 0.2%) yielded boron (B) intakes of <0.35 (control), 3, 6, 10, 13, or 25 mg B/kg body wt/d. Approximately one-half of the dams/group were terminated on gd 20, maternal whole blood collected and frozen, and prenatal outcome (fetal growth, viability, and morphology) evaluated. Remaining dams received control diet beginning on gd 20, and litters were monitored throughout lactation. Blood samples were prepared by a high-temperature alkaline ashing method and analyzed for B by inductively coupled plasma (ICP) optical emission spectrometry. On gd 20, blood B concentrations of 1.27 +/- 0.298 and 1.53 +/- 0.546 microg B/g were associated with the no-observed-adverse-effect level (NOAEL) and lowest-observed-adverse-effect level (LOAEL) (10 and 13 mg B/kg/d, respectively) for developmental toxicity. Developmental toxicity persisted postnatally only at 25 mg B/kg/d, a dose associated with >10-fold increase in maternal blood B (2.82 +/- 0.987 vs. 0.229 +/- 0.143 microg B/g for controls). Maternal blood B concentrations were: 1. Significantly elevated in all BA-exposed groups. 2. Positively correlated with maternal BA intake. 3. Inversely correlated with fetal body weight at doses above the NOAEL.

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