The Oxidative Potential Of Ambient Fine Particulate Matter And Its Association With Human Oxidative Stress Level

The exposure to ambient fine particulate matter(PM2.5)has led to an increase in the global burden of disease year by year,and has been the fifth major risk factor for the global burden of disease.However,the current air quality standards established by World Health Organization and China only impose restrictions on the mass concentration of PM2.5 without considering the differences in the composition of PM2.5 from different sources.The oxidative potential(OP)of PM2.5 describe the inherent abilities of particles or particle-bound components to produce reactive oxygen species(ROS)or oxidize substrates.The OP of particulate matter can not only reflect the redox activity of particulate matter components such as metals and organic chemicals,but also reflect the synergy or antagonism between different components.Therefore,compared with the PM2.5 mass concentration,OP is more closely related to the biological effects of particulate matter,and has been suggested to be used in epidemiological studies.However,there are still few epidemiological studies about OP at home and abroad.At the same time,it is still unclear whether the OP of PM2.5 measured under extracellular conditions can represent the actual oxidative stress level in the human body.Therefore,centered on the hot environmental particulate matter characteristic OP,our study explored the correlation between OP and the oxidative stress level of human and provided basic OP data in Baoding area,also provided the basis for further application of OP in human health risk assessment.Part 1:Analysis of the oxidative potential of ambient fine particulate matterObjective:This part of our research aimed to investigate the OP level of PM2.5 in Baoding area and seasonal differences,and explore the association between PM2.5 mass concentration and OP.Methods:Our research adopted a panel study design.Since May 2017,we recruited 120 healthy adult college students in Baoding city,a typical area of air pollution in China.We conducted four follow-up visits in different seasons,and conducted unified diet management and used individual portable air samplers to collect PM2.5 samples during each visit.We measured the PM2.5 mass concentration by weighing,and used dithiothreitol(DTT)analysis to determine the OP level of PM2.5.Repeated measurement analysis of variance was used to compare the differences in PM2.5 mass concentrations and OP levels in different seasons.The correlation between PM2.5 mass concentration and OP adopted Spearman rank correlation analysis.Results:(1)The annual average value of PM2.5 mass concentration collected at Baoding city was 183.12±67.11 ?g/m3 with significant seasonal variations ranking as Spring>Summer>Winter>Autumn(P<0.001).(2)The annual average value of DTTv(volume-normalized OP)was 3.95±2.07 nmol·min-1·m-3,The annual average value of DTTm(mass-normalized OP)was 23.75±14.74 pmol·min-1·?g-1.Both DTTv and DTTm had significant seasonal variations ranking as Spring>Summer>Autumn>Winter(P<0.01).(3)DTTv was positively correlated with PM2.5 mass concentration(r=0.30,P<0.05).There was no significant correlation between DTTm and PM2.5 mass concentration(r=0.09,P>0.05).Conclusions:From May 2017 to April 2018,the OP of PM2.5 in Baoding city was at a moderately high level,with significant seasonal differences.The OP of PM2.5 exposed to the environment(DTTv)was positively correlated with PM2.5 mass concentration,while the OP of intrinsic PM2.5 properties(DTTm)was uncorrelated with the PM2.5 mass concentration.Part 2:The effects of oxidative potential of ambient fine particulate matter on human oxidative stress levelObjective:This part of our research aimed to explore the association between PM2.5 mass concentration,OP and the human oxidative stress effects,also provided the basis for further application of OP in human health risk assessment.Methods:We conducted four follow-up visits in Baoding City,Hebei Province from May 2017 to April 2018.We collected venous blood samples from the subjects at the end of each follow-up.We used kits to detect the levels of four oxidative stress biomarkers in serum(OX-LDL,LPO,GSH-Px,T-AOC).The measurements of PM2.5 mass concentration and OP were same as above.We used face-to-face interview to obtain covariates such as demographic characteristics of the subjects.We used linear mixedeffects models to analyze the association between PM2.5 mass concentration,OP and biomarkers of human oxidative stress.Results:(1)PM2.5 mass concentration was significantly positively correlated with serum OX-LDL levels[%change:Q1=1;Q2=17.69(95%CI:1.05,37.07);Q3=21.29(95%CI:2.59,43.39)].DTTv and DTTm were significantly positively correlated with serum OX-LDL levels[%change:Ln DTTm=15.70(95%CI:7.17,24.90);Q1=1;Q2=36.37(95%CI:17.57,58.17);Q3=36.23(95%CI:17.19,58.37);Q4=53.34(95%CI:31.80,78.40)];[%change:Ln DTTv=19.70(95%CI:10.48,29.68);Q1=1;Q3=18.52(95%CI:1.23,38.76);Q4=54.28(95%CI:30.98,81.72)].No significant correlations were found between PM2.5 mass concentration,OP and serum OX-LDL levels under gender stratification.(2)No significant correlation was found between PM2.5 mass concentration and serum LPO level.DTTv and DTTm were significantly positively correlated with serum LPO levels[%change:Q1=1;Q2=16.52(95%CI:2.23,32.80);Q3=15.32(95%CI:0.84,31.87);Q4=25.27(95%CI:9.51,43.30)];[%change:Ln DTTv=7.67(95%CI:0.33,15.55);Q1=1;Q3=17.36(95%CI:1.72,35.41);Q4=23.76(95%CI:6.84,43.37)].These associations still existed under gender stratification.(3)PM2.5 mass concentration was significantly positively correlated with serum GSH-Px levels[%change:Q1=1;Q2=19.52(95%CI:1.07,41.33)].DTTv and DTTm were significantly positively correlated with serum GSH-Px levels[%change:DTTm:Q1=1;Q3=23.99(95%CI:4.60,46.97)];[%change:DTTv:Q1=1;Q3=20.71(95%CI:1.22,43.95)].Under gender stratification,only DTTm were significantly positively correlated with serum GSH-Px levels in women[%change:DTTm:Q1=1;Q3=31.71(95%CI:0.61,72.41)].(4)PM2.5 mass concentration was significantly positively correlated with serum TAOC levels only in women[%change:Q1=1;Q4=26.14(95%CI:5.72,50.50)].DTTv was significantly positively correlated with serum T-AOC levels[%change:Ln DTTv=4.85(95%CI:0.03,9.90)].Under gender stratification,only DTTv were significantly positively correlated with serum T-AOC levels in women[%change:Ln DTTv=10.37(95%CI:2.04,19.38);Q1=1;Q4=27.84(95%CI:6.95,52.81)].No significant correlation was found between DTTm and serum T-AOC level.Conclusions:Our study found that the OP of PM2.5 was significantly associated with the increase of serum OX-LDL,LPO,GSH-Px,and T-AOC.The PM2.5 mass concentration was only associated with the increase of serum OX-LDL and GSH-Px.Women might be more sensitive to health hazards caused by PM2.5.