The International Programme on Chemical Safety (IPCS) sponsored a collaborative study to examine the intra- and inter-laboratory variation associated with the preparation and bioassay of complex chemical mixtures. The mixtures selected were National Institute of Standards and Technology (NIST) Standard Reference Materials (SRMs). 20 laboratories worldwide participated in the collaborative trial. The participating laboratories extracted the organic portion of two particulate samples--an air-particulate sample and a diesel-particulate sample--and bioassayed the extracts. The laboratories simultaneously bioassayed a NIST-prepared extract of coal tar and two control compounds (benzo[a]pyrene, and 1-nitropyrene). The bioassay method used was the Salmonella/mammalian microsome plate-incorporation test using strains TA98 and TA100. Study design also allowed for a comparison of sonication and Soxhlet extraction techniques. The mean extractable masses for the air particles and diesel particles were approximately 5% and 17.5%, respectively. The particulate samples were mutagenic in both strains with and without activation in all 20 laboratories. For TA100 the with and without activation slope values for the air particulate were 162 and 137 revertants per mg particles, respectively. For TA98 the respective diesel slope values were 268 and 269. The mutagenicity slope values for the diesel particles ranged from 3090 (TA98, +S9) to 6697 (TA100, +S9) revertants per mg particles. The coal tar solution was negative for both strains when exogenous activation was not used but was mutagenic in both strains with exogenous activation. The benzo[a]pyrene and 1-nitropyrene were used as positive controls and gave results consistent with the literature. This paper provides a complete summary of the data collected during the collaborative study. Companion papers provide further analysis and interpretation of the results.

Air Pollutants↗

PubMedDate not supplied

Overview, conclusions, and recommendations of the IPCS collaborative study on complex mixtures.

The International Programme on Chemical Safety (IPCS) sponsored an international collaborative study to examine the variability associated with the extraction and bioassay of standard reference materials (SRMs) that are complex environmental mixtures provided by the U.S. National Institute of Standards and Technology (NIST). The study was also intended to evaluate the feasibility of establishing bioassay reference values and ranges for the SRMs. Twenty laboratories from North America, Europe, and Japan participated in the study. As part of the mandatory core protocol, each laboratory extracted the organic material from two particulate samples and bioassayed these extracts. A coal tar polycyclic aromatic hydrocarbon (PAH) solution and two mutagenic control compounds were also subjected to bioassay without prior extraction by the participating laboratories. The bioassay used was the Salmonella/microsomal plate incorporation assay. For the optional portion of the study, a laboratory was free to use the SRMs for any type of exploratory research. The primary purpose of the required portion of the study was to estimate the intra- and inter-laboratory variability in mutagenic potencies of the test materials and to determine whether or not the NIST mixtures could be used as reference materials by others performing the Salmonella assay. Repeatability (intra-laboratory variance) of the bioassay results ranged from 16% to 88% depending on the SRM and the bioassay conditions (tester strain and metabolic activation), whereas reproducibility (inter-laboratory variance) ranged from 33% to 152%. Between-laboratory variability was the main source of variation accounting for approximately 55-95% of the total variation for the three environmental samples. Variation in the mutagenic potency of the control compounds was comparable, with the exception of 1-nitropyrene for which the reproducibility ranged from 127% to 132%. In summary, NIST SRMs provided useful materials for an international inter-laboratory study of complex mixtures. By establishing both intra- and inter-laboratory variance for the mutagenicity results for these materials, the usefulness of these SRMs as reference materials for the Salmonella bioassay was established, critical procedures within the bioassay protocol were identified, and recommendations for future efforts were delineated.

International Cooperation↗

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The prevalence and frequency of drug use among Western Australian metropolitan high school students.

Data pertaining to prevalence and frequency of drug use were obtained from 1,394 Western Australian metropolitan high school students using a self-report questionnaire. Alcohol, marijuana, tobacco, hallucinogens, and amphetamines were reported as the most prevalent substances, with over 50% of "current drug users" using alcohol and marijuana on a frequent basis (i.e., weekly to more than once per day). Significant interactions existed between Gender and prevalence of tobacco and hallucinogens; and School Year Level and prevalence of tobacco, alcohol, hallucinogens and amphetamines. In terms of the frequency of use, significant interactions were found between Gender and marijuana; and between School Year Level and tobacco. Approximately 40% of substance-using participants used one single substance, 40% used two or three substances, and 20% used four or more substances. The results suggest there is a need for educators to have a greater understanding of the patterns of substance use in order for them to more aptly shape drug education programs.

Adolescent↗

PubMedDate not supplied

Plexiform neurofibromatosis of the orbit: CT evaluation.

Seven patients with orbital plexiform neurofibromas (PNFs) were evaluated by computed tomography (CT). These lesions are pathognomonic of von Recklinghausen disease and manifest a spectrum of radiologic abnormalities ranging from thickening of the eyelid and periorbital soft tissues to enlargement of the bony orbit and extensive infiltration of the orbital soft tissues. In analyzing the CT features of orbital PNF, three findings that have not been previously reported were identified. Increased density of the intraconal fat present in four of seven patients was believed to represent PNF involvement of small intraconal nerves. Three patients demonstrated enhancing, irregularly nodular thickening of the optic nerve sheath complex thought to be caused by PNF of the posterior ciliary nerves surrounding the optic nerve. Three patients with buphthalmos and congenital glaucoma demonstrated thickening and enhancement of the uveal/scleral layer believed to represent PNF of these structures. Involvement of the choroid and sclera, posterior ciliary nerves, and small intraconal nerves has been recognized pathologically but has not been previously identified by CT.

Adolescent↗

PubMedDate not supplied

The role of trauma in the pathogenesis of the osteochondroses.

Compression fracture of the secondary centers of ossification is an important factor in the pathogenesis of Perthes' disease and osteochondrosis dissecans. Avulsion fracture produces osteochondrosis affecting the non-articular epiphyses, e.g., Osgood-Schlatter disease. Some of these injuries appear to be produced solely by repetitive trauma and others may represent pathologic insult to constitutionally vulnerable or revascularizing bone, e.g., the femoral head in Perthes' disease.

Animals↗