In an attempt to define a tolerable daily intake (TDI) for molybdenum based on a toxicological risk analysis approach, a large literature survey was conducted. In man, absorption of molybdenum after oral intake is in the range of 28–77% and urinary excretion is 17–80% of the total dose. A low order of toxicity of molybdenum compounds has been observed in humans. However, with the available data, it is not possible to calculate any dose–response or dose–effect relationships. Because molybdenum toxicity is associated with copper intake or depleted copper stores in the body, humans who have an inadequate intake of dietary copper or some dysfunction in their copper metabolism that makes them copper‐deficient could be at greater risk of molybdenum toxicity. In the absence of relevant human studies, animal studies were evaluated for the derivation of the TDI. Effects of Mo on reproduction and foetal development were found to be critical effects observed in rats and mice. A dose–response relationship was observed in a study by Fungwe et al., with a ‘no observed adverse effect’ level (NOAEL) and a ‘lowest observed adverse effect’ level (LOAEL) of 0.9 and 1.6 mg Mo kg−1 day−1, respectively. Applying uncertainty factors of 10 for intraspecies and 10 for interspecies differences to the NOAEL, a TDI of 0.009 mg Mo kg−1 day−1 was calculated. The TDI is given a medium confidence rating. This TDI is more than double the upper limit of adequate intake for adolescents and adults that was derived from the Mo content of the average diet in the USA. Copyright © 1999 John Wiley & Sons, Ltd.

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In accomplishing their duties, firefighters are potentially exposed to a vast array of toxic combustion and pyrolysis products such as benzene, carbon monoxide, acrolein, nitrogen dioxide, and polycyclic aromatic hydrocarbons. Exposure to PAH and benzene was assessed by means of urinary measurements of 1-hydroxypyrene and t,t-muconic acid, respectively. All urine samples were collected from 43 firefighters during a period extending for 20 h following the end of exposure during a fire. A control sample was also obtained from each participant after at least four days without involvement in fire fighting activities. Only one control 1-hydroxypyrene measurement exceeded the value of 0.32 micromol/mol creatinine considered as the 95th percentile of a normal reference population in this study. Following exposure, 38 percent of the maximum values of all samples collected from each firefighter exceeded this reference value. The highest single value observed in this study was 3.6 micromol/mol creatinine. None of the control samples had a t,t-muconic acid concentration above the limit of detection. A large number (81%) of post-fire samples also had nonquantifiable concentrations of this metabolite. Among 43 firefighters in this study, 17 had measurable excretion of this metabolite in any of the urine samples after fire fighting and, of the latter group, only 6 had t,t-muconic acid concentrations exceeding 1.1 mmol/mol creatinine, a value considered to correspond to a benzene-air concentration of approximately 1 ppm according to the literature. There is clear evidence that fire fighting activities are associated with exposure to PAH above environmental background, as assessed by 1-hydroxypyrene measurements, despite the use of protective equipment. However, in comparison with observations made in other cohorts of industrial workers with known polycyclic aromatic hydrocarbons exposure, firefighters' exposure in this study was low. Similarly, based on t,t-muconic acid determinations, exposure to benzene was rather low in this study. For both contaminants, observation of low exposure could be due to either low concentrations of the contaminant during fire fighting or to the efficiency of protective equipment worn.

Technical variant techniques expand the pediatric donor pool and reduce time from listing to transplant, but they are associated with increased morbidity and mortality.

Biomonitoring Equivalents (BEs) are defined as the concentration of a chemical (or metabolite) in a biological medium (blood, urine, human milk, etc.) consistent with defined exposure guidance values or toxicity criteria including reference doses and reference concentrations (RfD and RfCs), minimal risk levels (MRLs), or tolerable daily intakes (TDIs) [Hays, S.M., Becker, R.A., Leung, H.W., Aylward, L.L., Pyatt, D.W., 2007. Biomonitoring equivalents: a screening approach for interpreting biomonitoring results from a public health risk perspective. Regul. Toxicol. Pharmacol. 47(1), 96-109]. The utility of the BE is to provide a screening tool for placing biomonitoring data into a health risk context. A Panel of experts took part in the Biomonitoring Equivalents Expert Workshop to discuss the various technical issues associated with calculating BEs and developed a set of guidelines for use in the derivation of BEs. Issues addressed included the role of the point of departure (POD) in BE derivation, the appropriate application of human and animal kinetic data and models, consideration of default uncertainty factor components in the context of internal dose-based extrapolations, and relevance of mode of action to technical choices in kinetic modeling and identification of screening values. The findings from this Expert Panel Workshop on BE derivation are presented and provide a set of guidelines and considerations for use in BE derivation.