Comparison of methods for personal sampling of inhalable and total lead and cadmium-containing aerosols in a primary lead smelter.

It has been proposed that future occupational aerosol exposure standards be based on particle size-selective sampling criteria that more accurately reflect worker exposure. In relation to methods currently used for determining individual workers' lead exposures, the widely used 37-mm, closed-face, plastic sampling cassette is known from laboratory wind tunnel studies to undersample significantly compared with estimations of aerosol actually inhaled, especially for large particles. The present study investigated the degree to which this is borne out in field sampling by using side-by-side sampling in selected work sites in a primary lead smelter. Exposures to "total" airborne lead and cadmium as measured using the 37-mm sampler (E37) were compared with exposure measurements using the institute of Occupational Medicine (IOM) personal inhalable aerosol sampler (EIOM). There were 166 good sample pairs for lead and 55 for cadmium. The ratio (reflecting the fractional undersampling of the 37-mm sampler, as represented by the ratio EIOM/E37) was consistently greater than unity, by factors obtained by regression analysis ranging (for different parts of the plant) from 1.39 to 2.14 for lead and 1.29 to 2.12 for cadmium. The factor tended to be greater for parts of the plant characterized by coarser aerosol, consistent with the physical sampling characteristics of the two instruments. This research is important (1) in assessing the impact of implementation of new standards for lead- and cadmium-containing aerosols in the primary lead production industry, and (2) in the development of new occupational exposure limits based on the inhalable aerosol fraction.

Antibiotic production and biocontrol activity by Bacillus subtilis CL27 and Bacillus pumilus CL45.

Bacillus subtilis CL27 and B. pumilus CL45 showed similar activity against Botrytis cinerea in in vitro plate assays. In a seedling bioassay, however, B. subtilis CL27 had activity similar to a commercial fungicide while B. pumilus CL45 failed completely to prevent seedling damping-off caused by Bot. cinerea. Antibiotic production by the two Bacillus strains was found to depend on the growth substrate and highest antibiotic production was found on media based on homogenized cabbage tissue. Antibiotic activity was found to depend on the pH and nutrient concentration in the assay medium. Antifungal antibiotics produced by B. subtilis CL27 and B. pumilus CL45 in different fermentation media were separated by thin layer chromatography. As suspected from the activity spectrum, three antibiotics (one with activity against Alternaria brassicicola, one with activity against Botrytis cinerea and one with activity against both fungi) could be detected in the fermentation broth of CL27, but only one in the fermentation broth of CL45. The two antibiotics produced by strain CL27 with activity against A. brassicicola were identified as peptides since their bands on the TLC plates developed a green to blue/green colour after treatment with 4,4'-tetramethyldiamino-diphenylmethane (TDM) reagent. The third antibiotics produced by strain CL27 and antibiotic produced by CL45 had a similar Rf-value and appeared not to be peptides based on the reaction with TDM. However, they showed a slightly different activity spectrum when tested against a range of different fungi. Antibiotic production was clearly indicated as the mode of action of in vivo biocontrol by strain CL27 against damping off caused by Bot. cinerea of Astilbe micro-plants, because a u.v.-induced antibiotic negative mutant strain CL27b showed no activity in seedling bioassays in vivo. Also the mutant strain CL27a which produced the two peptide antibiotics but had lost the ability to produce the non-peptide antibiotic, showed greatly reduced in vivo activity.

Perception of time-altered monosyllables in a specific group of phonologically disordered children.

Temporal auditory processing of open (e.g. pie) versus closed (e.g. pipe) syllables in a specific group of phonologically impaired children who deleted word-final consonants and normal phonologically developing children between the ages of 4 and 7 yr was investigated. The disordered group demonstrated significantly poorer discrimination at the faster but not slower rates of speech. Imitation of word-final consonants did not significantly increase in the disordered subjects when presented with time-expanded speech although certain individuals made noticeable improvements. Discussion of temporal auditory processing deficits from a neuropsychological perspective which suggests different etiologies is offered.