Monitoring diesel particulate matter and calculating diesel particulate densities using Grimm model 1.109 real-time aerosol monitors in underground mines.

Currently, there is no Mine Safety and Health Administration (MSHA)-approved sampling method that provides real-time results for ambient concentrations of diesel particulates. This study investigated whether a commercially available aerosol spectrometer, the Grimm Portable Aerosol Spectrometer Model 1.109, could be used during underground mine operations to provide accurate real-time diesel particulate data relative to MSHA-approved cassette-based sampling methods. A subset was to estimate size-specific diesel particle densities to potentially improve the diesel particulate concentration estimates using the aerosol monitor. Concurrent sampling was conducted during underground metal mine operations using six duplicate diesel particulate cassettes, according to the MSHA-approved method, and two identical Grimm Model 1.109 instruments. Linear regression was used to develop adjustment factors relating the Grimm results to the average of the cassette results. Statistical models using the Grimm data produced predicted diesel particulate concentrations that highly correlated with the time-weighted average cassette results (R(2) = 0.86, 0.88). Size-specific diesel particulate densities were not constant over the range of particle diameters observed. The variance of the calculated diesel particulate densities by particle diameter size supports the current understanding that diesel emissions are a mixture of particulate aerosols and a complex host of gases and vapors not limited to elemental and organic carbon. Finally, diesel particulate concentrations measured by the Grimm Model 1.109 can be adjusted to provide sufficiently accurate real-time air monitoring data for an underground mining environment.

The association of drinking water quality and sewage disposal with Helicobacter pylori incidence in infants: the potential role of water-borne transmission.

The mode of transmission of Helicobacter pylori, a bacterium causing gastric cancer and peptic ulcer disease, is unknown although waterborne transmission is a likely pathway. This study investigated the hypothesis that access to treated water and a sanitary sewerage system reduces the H. pylori incidence rate, using data from 472 participants in a cohort study that followed children in Juarez, Mexico, and El Paso, Texas, from April 1998, with caretaker interviews and the urea breath test for detecting H. pylori infection at target intervals of six months from birth through 24 months of age. The unadjusted hazard ratio comparing bottled/vending machine water to a municipal water supply was 0.71 (95% confidence interval (CI): 0.50, 1.01) and comparing a municipal sewer connection to a septic tank or cesspool, 0.85 (95% CI: 0.60, 1.20). After adjustment for maternal education and country, the hazard ratios decreased slightly to 0.70 (95% confidence interval: 0.49, 1.00) and 0.77 (95% confidence interval: 0.50, 1.21), respectively. These results provide moderate support for potential waterborne transmission of H. pylori.

Aerobic residential onsite sewage systems: an evaluation of treated-effluent quality.

This retrospective cohort study used existing data to evaluate the quality of effluent from three of the most common types of onsite residential aerobic treatment sewage systems (Multi-Flo, Norweco, and Whitewater) installed in Kitsap County, Washington. Five-day biochemical oxygen demand (BOD5), total suspended solids (TSS), and fecal-coliform-bacteria parameters were used to determine performance. Although most (77 percent) of the systems were less than one year old at the time of sampling, over a third failed to meet NSF certification standards for BOD5 and TSS in effluent (< 30 milligrams per liter [mg/L]). Over two-thirds of systems failed to meet Washington State Board of Health Treatment Standard 2 criteria for BOD5 and TSS (< 10 mg/L). Furthermore, an average of 59 percent of the systems failed to meet state standards for fecal coliform (< 800 fecal coliform bacteria per 100 milliliters).