Contribution of the gasoline distribution cycle to volatile organic compound emissions in the metropolitan area of Mexico City.

Gasoline distribution in the metropolitan area of Mexico City (MAMC) represents an area of opportunity for the abatement of volatile organic compound (VOC) emissions. The gasoline distribution in this huge urban center encompasses several operations: (1) storage in bulk and distribution plants, (2) transportation to gasoline service stations, (3) unloading at service stations' underground tanks, and (4) gasoline dispensing. In this study, hydrocarbon (HC) emissions resulting from breathing losses in closed reservoirs, leakage, and spillage from the operations just listed were calculated using both field measurements and reported emission factors. The results show that the contribution of volatile HC emissions due to storage, distribution, and sales of gasoline is 6651 t/year, approximately 13 times higher than previously reported values. Tank truck transportation results in 53.9% of the gasoline emissions, and 31.5% of emissions are generated when loading the tank trucks. The high concentration of emissions in the gasoline transportation and loading operations by tank trucks has been ascribed to (1) highly frequent trips from distribution plant to gasoline stations, and vice versa, to cope with excessive gasoline sales per gasoline station; (2) low leakproofness of tank trucks; and (3) poor training of employees. In addition, the contribution to HC evaporative and exhaust emissions from the vehicles of the MAMC was also evaluated.

Contribution of LPG-derived emissions to air pollution in the metropolitan area of Guadalajara City.

Measurements of hydrocarbon (HC) emissions generated by the use of liquefied petroleum gas (LPG) in the metropolitan area of Guadalajara City (MAG) are presented in this work. Based on measurements in the course of distribution, handling, and consumption, an estimated 4407 tons/yr are released into the atmosphere. The three most important contributors to LPG emissions were refilling of LPG-fueled vehicles and commercial and domestic consumption. The MAG shows a different contribution pattern of LPG emission sources compared with that of the metropolitan area of Mexico City (MAMC). These results show that each megacity has different sources of emissions, which provides more accurate strategies in the handling procedures for LPG to decrease the impact in O3 levels. This work represents the first evaluation performed in Guadalajara City, based on current measurements, of the LPG contribution to polluting emissions.

Accuracy of the Welch Allyn AudioScope and traditional hearing screening for children with known hearing loss.

The Welch Allyn AudioScope is a new screening instrument that allows both audiometric testing at 500, 1000, 2000, and 4000 Hz at 25 dB hearing level and otoscopic examination. Sixty-eight patients between 3 and 9 years of age with normal hearing or a variety of hearing losses comprised the study population. Immediately after receiving an audiologic evaluation the subjects were screened with a traditional screening audiometer and two examinations with the AudioScope, performed in a clinic examining room by pediatricians and nurse practitioners unaware of the children's hearing status. The AudioScope was as accurate as traditional hearing screening in identifying children with normal hearing and those with hearing loss. Log-linear modeling demonstrated that the results of AudioScope testing were similar to those of traditional hearing screening. However, the false positive rate was higher at 500 Hz for the first AudioScope examination, suggesting the need for two AudioScope tests. The AudioScope was quick and easy to use, nonthreatening to the subjects, less expensive than a pure-tone screening audiometer, and does not require a sound-treated room.