Personal exposure to benzene, toluene and xylene in different microenvironments at the Mexico City metropolitan zone.

The Mexico City Metropolitan Zone (ZMCM) population's exposure to benzene, toluene and xylene was measured at different microenvironments to establish basic indicators of the presence and effects of these characteristic volatile organic compounds (VOC). In particular, VOC personal exposures were measured in different microenvironments during a 5-day working week, with 12-h daily periods. We have found a good agreement of our results with the registered VOC levels of the Metropolitan Automated Monitor System (RAMA) for the corresponding period. From our results, we expect to generate useful information to evaluate the health effects of these VOCs on exposed people.

Atmospheric volatile organic compound measurements during the 1996 Paso del Norte Ozone Study.

Ambient air VOC samples were collected at surface air quality monitoring sites, near sources of interest, and aloft on the US (El Paso) and Mexican (Ciudad Juárez) side of the border during a six-week period of the 1996 Paso del Norte Ozone Study. Samples were collected at five sites, three on the US side and two on the Mexican side, during nine intensive operation days when high ozone levels were forecast for the area. Six other sites were sampled to characterize up-wind, down-wind and other emission sources. Samples for determining source profiles were collected for rush hour traffic, propane-powered bus exhaust, automobile paint shop emissions, propane fuels, and industrial manufacturing in Cd. Juárez and a refinery in El Paso. Most samples were collected in electro-polished stainless steel canisters for determination of C2 to C(10+) hydrocarbons by GC-FID. Carbonyl samples were collected on DNPH impregnated cartridges at three surface sites during aircraft flights and analyzed by HPLC. This paper presents the spatial and temporal characteristics of VOC species concentrations and compositions to examine the differences and similarities of the various locations and time periods. Overall surface, total non-methane hydrocarbon values ranged from 0.1 to 3.4 ppmC with the highest concentrations being recorded in the morning and evening at five vehicle-dominated sites, three in Cd. Juárez and two in El Paso. Toluene in El Paso samples and propane, which is used as a cooking and transportation fuel in Cd. Juárez, were the most abundant hydrocarbons. The most abundant carbonyls were acetaldehyde, acetone and formaldehyde.

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.

Particulate Air Pollution in Mexico City: A Collaborative Research Project.

PM10, PM25, precursor gas, and upper-air meteorological measurements were taken in Mexico City, Mexico, from February 23 to March 22, 1997, to understand concentrations and chemical compositions of the city's particulate matter (PM). Average 24-hr PM10 concentrations over the period of study at the core sites in the city were 75 H g/m3. The 24-hr standard of 150 µ g/m3 was exceeded for seven samples taken during the study period; the maximum 24-hr concentration measured was 542 µ g/m3. Nearly half of the PM10 was composed of fugitive dust from roadways, construction, and bare land. About 50% of the PM10 consisted of PM2.5, with higher percentages during the morning hours. Organic and black carbon constituted up to half of the PM2.5. PM concentrations were highest during the early morning and after sunset, when the mixed layers were shallow. Meteorological measurements taken during the field campaign show that on most days air was transported out of the Mexico City basin during the afternoon with little day-to-day carryover.

[Survey of physicians' attitudes to terminal patients]. / Encuesta de actitudes médicas ante el paciente terminal.

OBJECTIVE: To explore the opinion of physicians about euthanasia and the treatment of dying patients. DESIGN: A comparative survey. MATERIAL AND METHODS: We interviewed 38 family physicians (FP), 38 specialty physicians (SP) and 38 medical students (MS). The survey had 30 items, five of them about experience with terminal patients which were not used for the students. ANALYSIS: Descriptive statistics and chi 2 or Fisher test to compare proportions between groups. RESULTS: One hundred and two (89%) of the interviewed had a correct concept of euthanasia; 105 (92%) thought that life is holy and untouchable; 29 (25%) agreed there are persons more valuable than others, and four (4%) consider that some should die in certain situations. In relation to patients with brain death, 79 (69%) believed they should not receive futile treatment, but 42 (37%) said they should be attended until cardiac arrest occurred. All agreed with the need of the patients to receive comfort and peace, but only 49/76 (64%) of the physicians and 28 (74%) of the students were in favor of sending dying patients to their home. Nine FP (23%) and 14 SP (36%) stated that in many occasions they lacked elements to solve ethical dilemmas. Thirty six (32%) agreed with the use of passive euthanasia and 21 (18%) with active euthanasia; the latter was more frequent among students. Nine FP (24%) and 13 SP (34%) said they had exceeded therapy sometimes and 23 (61%) of the FP and 19 (50%) of the SP considered they had stopped treatment too early in some cases. We found no differences in regard to euthanasia between physicians and students (chi 2 = 0.32, p = 0.71) nor between the physicians with frequent vs occasional contact with terminal patients (Fisher = 0.13). CONCLUSIONS: A third of the physicians agreed with some form of euthanasia but this frequency is smaller than that in other countries.

[The echographic dimensions of the liver in the term newborn and its relation to anthropometric variables]. / Dimensiones ecográficas del hígado del recién nacido a término y su relación con variables antropométricas.

We decided to undergo a study looking for normal liver size in relation with other anthropometric measures. Fifty healthy, appropriate for gestational age term-babies, born at the Hospital de Ginecopediatría Número 48, Centro Médico Nacional del IMSS, León, Guanajuato, México, were examined by hepatic ultrasound. The vertical diameter was 6.0 +/- 0.75 cm, transverse 8.26 +/- 0.72 cm, AP 5.44 +/- 0.5 cm. The longitudinal cross section area was 16.21 +/- 2.5 cm2, and the transverse cross section area 22.53 +/- 3.4 cm2. We found most important correlation between vertical diameter and longitudinal cross section area with the anthropometric measures. The hepatic measures correlate better with the weight. Ultrasound provides a rapid, accurate and convenient method for study the liver size and morphology in the neonate.

[The incidence of external congenital malformations at the Hospital de Ginecopediatría No. 48 in León, Guanajuato]. / Incidencia de malformaciones congénitas externas en el Hospital de Ginecopediatría No. 48 en León, Guanajuato.

From June 1st, 1989 to May 31st, 1990, 16,987 consecutive newborns were examined at the No. 48 Gynecological Pediatric Hospital of the IMSS National Medical Center, looking for external congenital malformations including esophageal atresias, anorectal malformations and congenital hip luxations, all easily detected during a routine exploration. Each deformed newborn assigned two control patients the following two newborn babies showing no birth defects. 308 deformed newborns were detected, an incidence of 1.81%. Among the most frequent defects were midline flat hemangiomas, polyotia, Down syndrome, congenital hip luxation and myelomeningocele. The only significant statistical difference found with respect to the control group was a greater family history of defects in the case group (P less than 0.0001). When comparing our results with those from other studies, including a study done locally 15 years ago, we found differences among specific malformations: congenital hip malformation, polydactylia, foot deformities, flat hemangiomas, nevus and polyotias. Yet, the overall frequency of defects found was similar.