Particulate matter from diesel exhaust (DPM) is a pollutant of increasing concern, but its concentrations are difficult to measure in the environment. There are no unique chemical characteristics for DPM, so elemental carbon (EC) and black carbon (BC) measurements have historically been used to estimate its concentrations. However, both methods have limitations, and neither is capable of identifying specific sources. That results in significant uncertainties in the inferred DPM concentrations. In this study an intentional fuel-based tracer, iridium, was used to mark the DPM from a school bus's exhaust. Emissions tests established the mass ratio of DPM-iridium in the exhaust. Iridium measurements inside the bus during normal operations could then be used to calculate DPM concentrations without the limitations of methods relying on nonspecific markers. Previous studies have attributed in-bus concentrations of more than 30 μ/m3 to the bus's exhaust, but they relied on nonspecific methods with a sensitivity of approximately 0.1 μ/m3. In this study the average measured DPMSB concentration was 0.22 μ/m3—about 1% of previous estimates. Measurement sensitivity was approximately 0.001 μ/m3—100 times better than that of other methods. The sensitivity and specificity achieved show that this tracer method can resolve major ambiguities and uncertainties in estimates of actual DPM concentrations. The ability to estimate accurately the contributions of different sources to DPM concentrations provides a needed tool to evaluate proposed emission reduction strategies reliably.

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Background: The association between infertility and sperm disomy is well documented. Results vary but most report that men with severely compromised semen parameters have a significantly elevated proportion of disomic sperm. The relationship between individual semen parameters and segregation of specific chromosome pairs is however less well reported as is the variation of disomy levels in individual men.

The chemistry, microbiology, pharmacokinetics, adverse reactions, and clinical indications for cefsulodin are reviewed and compared to ceftazidime and cefoperazone. Cefsulodin is a narrow-spectrum, third-generation cephalosporin with activity virtually restricted to Pseudomonas aeruginosa. Cefsulodin is eliminated renally and has a serum half-life similar to ceftazidime and cefoperazone. Cefsulodin appears to be well tolerated and relatively free of any significant toxicity except for nausea and vomiting, which appear to be related to the infusion rate. Cefsulodin may be beneficial in those rare clinical situations where an infection is caused by a sensitive isolate of P. aeruginosa known to be resistant to the other antipseudomonal cephalosporins, and/or the avoidance of an aminoglycoside antibiotic is desired. However, its empiric use is to be discouraged.

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