Summary of the NIOSH guidelines for air sampling and analytical method development and evaluation.

Suggested guidelines for the development and evaluation of sampling and analytical methods for industrial hygiene monitoring have recently been published in a NIOSH technical report. These guidelines are based in part on various published approaches for method development and evaluation and serve as an attempt at a more unified experimental approach. This paper presents some salient features of this unified approach for method development and evaluation. The basic goal of the approach is to determine if the method under study meets the criterion to produce a result that fell within 25% of the true value 95 times out of 100 on average, although other factors of method performance are evaluated. The experiments proposed for the evaluation of method performance include determination of analytical recovery from the sampler, sampler capacity, storage stability of samples and effect of environmental factors. Evaluation criteria for the experimental data and procedures for the calculation of method bias, precision and accuracy are also included.

Evaluation of a chemical spot-test kit for the detection of airborne particulate lead in the workplace.

A commercial rhodizonate-based test kit was evaluated for its potential use in the detection of lead in airborne particulate samples at work sites. Over 350 air samples were collected at abrasive blasting lead paint abatement sites using cellulose ester membrane filters and personal sampling pumps. The filter samples were tested with the chemical spot test and then analyzed by graphite furnace atomic absorption spectrophotometry. No positive readings were recorded for lead masses below 1.3 micrograms Pb/filter, and no negative readings were observed for lead amounts above 8.1 micrograms Pb/filter. Experimental data were statistically molded in an effort to estimate the performance parameters of the spot test kit. The identification limit of the kit was found to be approximately 3.6 microgram/filter sample. For lead mass values above approximately 10 micrograms Pb/filter, 95% confidence of a positive reading was found, while 95% confidence of a negative reading was found for lead masses below approximately 0.6 micrograms Pb/filter. Based on the results of this study the rhodizonate-based test kit for lead demonstrates potential for use in field screening for lead in personal breathing zone and area air samples.

Investigation of the ability of MDHS method 25 to determine urethane-bound isocyanate groups.

Method 25 for the Determination of Hazardous Substances (MDHS 25) of the Health and Safety Executive of the United Kingdom attempts to identify and quantify all isocyanate species in an air sample. Isocyanate species are derivatized with 1-(2-methoxyphenyl)piperazine (MOPP) and analyzed by high-performance liquid chromatography (HPLC) with tandem ultraviolet/electrochemical (UV/EC) detection. The method identifies peaks as being isocyanate-derived if the EC/UV detector response ratio is between 0.75 and 1.5 times that of the derivatized monomer. This investigation sought to determine if the method correctly identifies and accurately quantifies intermediates created during polyurethane formation that possess free isocyanate groups. Model compounds derived from 2,4-toluene diisocyanate (2,4-TDI) and ethylene glycol were prepared. These urethane species contained two ("dimer") and three ("trimer") TDI units and terminal MOPP-derivatized isocyanate groups. Like monomeric 2,4-TDI/MOPP urea, each contained two derivatized isocyanate groups per molecule. This investigation found that neither the UV nor the EC response is proportional to the number of isocyanate groups present in the model compounds. Therefore, it is concluded that MDHS 25 is neither capable of correctly identifying TDI-urethane intermediates possessing MOPP-derivatized isocyanate groups nor is it capable of accurately quantifying these isocyanate groups. The proposed solution to this problem is the utilization of a derivatizing reagent that yields derivatized isocyanate species whose detector responses come more exclusively from the derivatized isocyanate moiety and, therefore, are more proportional to the number of derivatized isocyanate groups.

Magnetic resonance imaging of glenohumeral instability.

Glenohumeral instability refers to subluxation or dislocation of the glenohumeral joint. This painful disorder is particularly common in the athletic population, and the individual with instability may present with a variety of clinical complaints. This paper addresses current theories regarding the pathophysiology of glenohumeral instability and illustrates magnetic resonance findings that can assist in diagnosis and treatment planning.

Acidic-phosphoprotein phosphatase activity of rat ventral prostate nuclei: apparent lack of effect of androgens.

A protein phosphatase activity has been demonstrated in nuclei of rat ventral prostate utilizing 32P-labelled phosvitin as a model acidic phosphoprotein substrate. This phosphoprotein phosphatase has a pH optimum of 6.7, is unaffected by the sulphydryl protecting agent 2-mercaptoethanol, and requires a divalent cation for maximal activity. Of the various divalent cations tested, Mg2+ is the most effective in reactivating the EDTA-inhibited enzyme. The phosphatase is inhibited by sodium flouride, sodium oxalate, N-ethylmaleimide, ATP and ADP but is relatively insensitive to ammonium molybdate. Increased ionic strength of the reaction medium also causes a reduction in the enzyme activity, e.g., by 48% at 200 mM sodium chloride. The activity of the acidic phosphoprotein phosphatase did not change significantly at 48 h or 96 h post-orchiectomy when expressed per unit of nuclear protein. However, it is reduced by approx. 30% at these times after castration if based on DNA content. The decline in activity per nucleus reflects the decrease in the realtive nuclear protein content observed at 48 h or 96 h post-orchiectomy. This suggests that the decline in the phosphorylation of prostatic nuclear acidic proteins which occurs upon androgen withdrawal is not due to increased nuclear phosphatase activity.