Impact Of Travel Behavior On Air Pollution Exposure And Associated Health

Ambient fine particulate matter has become primary air pollutants in most Chinese cities.According to PM2.5 source apportionment in many cities,motor vehicle emissions have been an important contributor.The rapid increase in the proportion of motor vehicle emissions reflects the change of residents’travel behavior with uncertain impacts on air pollution exposure and associated health.In order to accurately assess the impacts of travel behavior changes on health and provide support for the government to make more scientific transportation policies,this study measured concentratons of fine particles in typical transportation microenvironments(namely:walking/bicycle/motorcycle,bus,metro,private car/taxi)during four seasons in the main city of Nanjing using the method of microenvironment measurement and time-activity patterns survey.Main conclusions are as follows:i.Walking/bicycle/motorcycle had the highest averaged real-time PM2.5 concentration of 139.47 μg/m3,followed by bus and metro with PM2.5 concentration of 68.89 μg/m3and 53.60 μg/m3 over four seasons.Car/Taxi had the slightest PM2.5 concentration of 52.60 μg/m3.After modified by corresponding ambient PM2.5 concentrations,the results showed that the PM2.5 concentrations of in-cabin modes were generally lower than those of on-roadway modes.This is consistent with the findings in China-based studies but contrary to those in developed countries due to the significant disparities in ambient air pollution levels.ii.To explore the modification effects of different factors,this study found:First,season had a strong effect on the PM2.5 concentrations in transportation microenvironments,with the lowest concentrations in summer and the highest in winter(exception of car/taxi in spring).Second,in spring,PM2.5 concentrations in walking/bicycle/motorcycle modes were higher than those in bus,followed by car/taxi and metro.In summer,concentrations in walking/bicycle/motorcycle modes were higher than those in metro,followed by car/taxi and bus-In autumn and winter,concentrations in walking/bicycle/motorcycle modes were higher than those in bus,followed by metro and car/taxi.When ambient PM2.5 levels were below 25 μg/m3,concentrations in walking/bicycle/motorcycle modes were higher than those in metro,followed by car/taxi and bus.When ambient PM2.5 levels were between 25 and 75μg/m3,concentrations in walking/bicycle/motorcycle modes were higher than those in bus,followed by metro and car/taxi.When ambient PM2.5 levels were above 75μg/m3,concentrations in walking/bicycle/motorcycle Iodes were higlher than those in bus,followed by car/taxi and metro.Third,air conditioning can effectively reduce exposure levels while opening window will increase microenvironment PM2.5 concentrations.Based on that,we recommend that government should encourage residents to take more buses in summer or when ambient air pollution concentrations are below 25 g.g/m3.In other cases,car/taxi or metro seems to be the first choice.Especially in heavy-polluted days(>75gg/m3)5 metro should be highly recommended by the government.iii.Residents in the main city of Nanjing were exposed to an increase dose of 1662.17 μg·104 persons from 2010 to 2014.Based on the localized Dose-Response Function,an increase of 2.4(95%CI:2.0,2.8)deaths were occurred in 2014 due to travel behavior changes,among which changes on travel pattern and time spent in different modes contributed to positive health effects,offset by adverse health effects induced by increase in travel volume and ambient PM2.5 concentration.