Personal exposure to particulate matter less than 2.5 μm in Mexico City: a pilot study

Abstract

This study was aimed to describe the personal exposure of permanent residents in Mexico City's Metropolitan Area (MCMA) to particulate matter of less than 2.5 mm diameter (PM 2.5 ) during their daily activities. A total of 40 healthy volunteers (30 women and 10 men) with sedentary activities were included. All of them carried a PM 2.5 personal monitor during 13 h and registered their activities in a written diary that classified them in indoor and outdoor microenvironments in each 30 min period. All sample collections started at 0900 hours, and even though measurements were obtained during the rainy season (April-August 2002), the relative humidity was less than 70%. The data were categorized and evaluated under the following criteria: morning and afternoon exposure, indoor and outdoor activities, and geographical location. The descriptive analysis showed that the overall outdoor median concentration of PM 2.5 (89.50 mg/m 3 ) was higher than the indoor one (67.55 mg/m 3 ). PM 2.5 concentrations in the morning to early afternoon were more elevated than in the late afternoon, suggesting a circadian-like behavior. In the indoor microenvironment, the highest concentration occurred in the subway (106.2 mg/m ). All the differences were statistically significant (Po0.05). Multivariate analysis corroborated that PM 2.5 concentrations are mainly determined by geographical locations and hour of the day, but not by the type of microenvironment. The inclusion of covariables in the multivariable analysis ensures a more accurate estimation and prediction of the real PM 2.5 concentrations. In conclusion, PM 2.5 personal exposure of healthy adult permanent residents of MCMA is usually higher than recommended by the international standards in outdoor and even in indoor microenvironments. Particulate matter personal exposure varies in relation to hour of the day, daily activities and microenvironments.

Personal Exposure to PM2.5 in the Megacity of Mexico: A Multi-Mode Transport Study

“…The median exposure levels reported here for public buses and CC are lower than those reported in the MCMA by Vallejo et al [12] of 101.7 and 62.4 µg m −3 , respectively. However, the average exposure levels reported here are within the range of those reported by Okokon et al [9] (14 ± 5 to 85 ± 39 µg m −3 ) in three European cities for bicycle, public bus and car with open and closed windows.…”

“…In the MCMA, studies have addressed personal exposure to carbon monoxide with the highest and lowest levels observed for private and public transport, respectively [10], and to volatile organic compounds with exposure levels to vehicular related compounds being a factor of 2 greater than observed indoors [11]. Vallejo et al [12] addressed personal exposure to PM 2.5 during transportation within the MCMA by underground, public bus and private car, reporting median exposure levels of 106.2, 101.7 and 62.4 µg m −3 , respectively; however, their study design did not allow for comparison between micro-environment concentrations. This highlights the importance of assessing personal exposure to PM 2.5 during daily commutes using comparable information of modes of transport and routes.…”

Ambient fine particles modify heart rate variability in young healthy adults

“…No data about daily temperature or other pollutants concentrations were used because they were not always available from net monitors. Details of personal exposure data were published elsewhere (Vallejo et al, 2004).…”

An Approach to the Study of Transport and Dispersion of Threat Agents in a Subway Station

“…One such example is the TEACH (Toxic Exposure Assessment, Columbia/Harvard) study, which measured particle composition in a subway station and in a subway car and observed that the highest exposures occurred in the station (Chillrud et al, 2004). Vallejo et al (2004) placed personal samplers for particulate matter with 50% having aerodynamic mass diameter less than 2.5 µm (PM2.5) on 40 volunteers who recorded their daily activities in 30 minute intervals over a 4-month period. This study demonstrated PM2.5 exposure to be highest during the period when participants rode the subway, although the sampling interval was too large to distinguish times waiting on the platform from times riding in the subway cars.…”