Joel C. Harrison

Genotoxicity of diesel-exhaust particles dispersed in simulated pulmonary surfactant

Diesel-exhaust particles from two sources were dispersed in aqueous mixtures of dipalmitoyl phosphatidyl choline, a major component of pulmonary surfactant, and were tested for genotoxicity. Diesel samples from the same sources were extracted with dichloromethane and transferred into dimethyl sulfoxide and subjected to the same assays. Both types of extractions yielded similar results in both the Salmonella mutagenicity assay and the sister-chromatid exchange assay using V79 cells. After separation of the samples into supernatant and sediment fractions, the activity of both diesel samples was shown to reside exclusively in the supernatant fraction for the solvent-extracted samples, and exclusively in the sedimented fraction for surfactant dispersed samples. These findings indicate that genotoxic activity associated with diesel particles inhaled into the lung may be made bioavailable by virtue of the solubilization/dispersion properties of pulmonary surfactant components.

Susceptibility of High-density Polyethylene/wood-flour Composite to Mold Discoloration

Abstract High density polyethylene (HDPE)/wood-flour composites containing either pine or maple flour were evaluated for susceptibility to mold colonization and discoloration using two different ASTM standards: ASTM standards D4445 and G21. Some test specimens were pre-exposed to accelerated ultraviolet weathering and freezethaw cycles and these were air-dried before exposure to molds in either ASTM D4445 or G21. Mold colonization on the surface of exposed samples was visually rated. Wood plastic composites containing either pine or hard maple exhibited greater fungal colonization and discoloration in the ASTM G21 test than the ASTM D4445. Consequently, the ASTM standard G21 was a more sensitive and better test protocol for evaluating the susceptibility of HDPE/wood-flour composite to mold discoloration. It is evident that constant or frequent moisture presence is necessary for the growth and support of mold colonization and discoloration of HDPE/woodflour composite. Pre-conditioning of HDPE/wood-flour composites to accelerated UV weathering or freeze thaw cycles had no discernible effect on susceptibility to mold discoloration. Environmental scanning electron microscopic analysis of the surface of HDPE/wood-flour composite clearly indicated that wood flour is not completely encapsulated by the HDPE matrix and exposed wood flour may serve as points for moisture adsorption and fungal colonization.

Surface Properties of Respirable Silicate and Aluminosilicate Dusts Affecting Bioavailability

Pure respirable quartz is a known pathogenic agent for lung disease. However, for mixed dusts, neither mineralogical nor, in vitro, cytotoxicity assays unequivocally predict the contribution of quartz to their pathogenic potential.

Possible role of regional variation in allergic contact dermatitis: case report

A 27-year-old male presented to our dermatitis clinic with 6 months’ duration of red oedematous lesions on his ankles. He was previously treated for this suspected allergic contact dermatitis with prednisone (30 mg daily) for 2 weeks, during which time these lesions cleared. However, upon prednisone discontinuation the lesions recurred within several days. Physical examination showed symmetrical red, oedematous and scaling lesions on the patient’s anterior and lateral ankles bilaterally. The dorsa of his feet and his soles were clear, and no psoriatic stigmata were observed. Working diagnoses considered at this point were atypical tinea and possible allergic contact dermatitis. KOH scraping for fungi gave a negative result. Patch testing was performed with the baseline series of the ICDRG (1). Finn Chambers® were placed on the upper back, and read on day (D) 2 and D4; the ICDRG scoring system was used (maximum of +++). All patch tests gave negative results on D4, except for potassium dichromate 0.5% pet. (++) and cobalt chloride 1% pet. (++). Repeat patch testing was performed with potassium dichromate 2% pet., and gave a positive result (++). The National Institute for Occupational Safety and Health (NIOSH) was consulted, and samples of the patient’s leather footwear were sent to the NIOSH for evaluation of total chromium (Cr) content in the ankle and dorsal foot area. Cr contents of a leather boot were analysed with inductively coupled plasma mass spectrometry (ICP-MS) (NexION 300D; Perkin-Elmer, Waltham, MA, USA) after acid digestion. All glassware was cleaned

A chamber study of alkyl nitrate production formed by terpene ozonolysis in the presence of NO and alkanes

Organic nitrates are relatively long-lived species and have been shown to have a potential impact on atmospheric chemistry on local, regional, and even global scales. However, the significance of these compounds in the indoor environment remains to be seen. This work describes an impinger-based sampling and analysis technique for organic nitrate species, focusing on formation via terpene ozonolysis in the presence of nitric oxide (NO). Experiments were conducted in a Teflon film environmental chamber to measure the formation of alkyl nitrates produced from α-pinene ozonolysis in the presence of NO and alkanes using gas chromatography with an electron capture detector. For the different concentrations of NO and O3 analyzed, the concentration ratio of [O3]/[NO] around 1 was found to produce the highest organic nitrate concentration, with [O3] = 100 ppb & [NO] = 105 ppb resulting in the most organic nitrate formation, roughly 5 ppb. The experiments on α-pinene ozonolysis in the presence of NO suggest that organic nitrates have the potential to form in indoor air between infiltrated ozone/NO and terpenes from household and consumer products.