Spatial and temporal determinants of particulate matter peak exposures during pregnancy and early postpartum.

Background: Fine particulate matter (PM) exposure is an important environmental risk for maternal and children's health, with peak exposures especially those derived from primary combustion hypothesized to pose greater risk. Identifying PM peaks and their contributions to personal exposure remains challenging. This study measured personal PM exposure, characterized primary combustion peaks, and investigated their determinants during and after pregnancy and among Hispanic women in Los Angeles, CA.

Methods: Continuous personal PM exposure, Global Positioning System geolocation, and ecological momentary assessment surveys were collected from 63 women for 4 consecutive days in their 1 trimester, 3rd trimester and 4-6 months postpartum. Based on the shape of PM time-series, primary combustion peaks were identified, characterized (number, duration, area under the curve [AUC]), and linked with locations they occurred in. Zero-inflated generalized mixed-effect models were used to examine the spatial and temporal determinants of PM peak exposures.

Results: A total of 490 PM peaks were identified from 618 person-days of monitoring. Spending an additional minute at parks and open spaces was related to smaller (AUC decreased 3.1 %, 95 % CI: 1.5 %-4.6 %) and shorter (duration decreased 1.7 %, 0.5 %-2.9 %) PM peak exposure. An additional minute in vehicular trips also related to smaller and shorter peak exposure (AUC and duration decreased 2.5 %, 1.2 %-3.7 % and 1.8 %, 1.0 %-2.6 %, respectively). However, an additional minute at industrial locations was associated with greater number (3.6 %, 2.0 %-5.2 %), AUC (1.6 %, 0.1 %-3.2 %) and duration (1.0 %, 0.0 %-2.1 %) of personal PM peak exposure.

Conclusions: This study demonstrates the potential to statistically identify exposure to primary combustion PM peaks and understand their determinants from personal monitoring data. Results suggest that visits to parks and open spaces may minimize PM peak exposures, while visiting industrial locations may increase them in and around pregnancy.