| As an important adsorption carrier of pollutants,dust can adsorb up to 100kinds of environmental pollutants,including heavy metals(such as Cd,Pb,Cu and Cr)and organic pollutants(such as phthalates,etc.),which pose a great threat to the environment and exposed people.This problem has been widely concerned by researchers around the world.At present,the single pollution characteristics of heavy metals and phthalates in dust and their health effects on the exposed population have been widely studied,but the report on the combined pollution of the heavy metals and phthalates is seldom seen.However,dust is usually the coexistence of organic and inorganic pollutants.Therefore,it is significant to carry out the researches on the compound pollution of heavy metals and phthalates in terms of protecting the ecological environment and human health.Based on the above research background,dust samples were collected in urban residential area of typical old industrial city Changchun,and carries on the sample collection and research in its corresponding outdoor location.The pollution characteristics of heavy metals and phthalates in dust and their effects on and toxicological effects and human health were investigated.The results can not only provide a scientific basis for elucidating the pollution characteristics of dust in Changchun,but also provide an important theoretical evidence for the development of prevention and control measures to due with the population health problems caused by dust exposure.The specificwork of this program is as follows:(1)In this study,50 sampling points were set up in the five districts of Changchun City to collect indoor and outdoor dust samples of residential areas,and the contents of 6 heavy metals(Zn,Cr,Ni,Cu,Cd and Pb)as well as 16 phthalates were determined.The differences and correlations of accumulation of heavy metals and phthalates in indoor and outdoor dust were compared.The results showed that the average contents of Zn,Cr,Ni,Cu,Cd and Pb in indoor dust were 358 mg·kg-1,41.8 mg·kg-1,23.9 mg·kg-1,54.5 mg·kg-1,1.22 mg·kg-1 and 61.2 mg·kg-1,respectively;the average contents of Zn,Cr,Ni,Cu,Cd and Pb in outdoor dust were129 mg·kg-1,45.8 mg·kg-1,16.5 mg·kg-1,25.6 mg·kg-1,0.37 mg·kg-1 and 33.6mg·kg-1,respectively.The content and contamination level of heavy metals in indoor dust of Changchun City were higher than that of outdoor dust.The pollution level of Cd is in the highest level in this study.Cd is in the medium strong pollution level and strong pollution levelin most indoor dust and outdoor dust,respectively.In addition,dust was contaminated by other heavy metals to some degree except Cr and Ni.Nine phthalate esters(DEHP,Di BP,DNBP,DMP,DEP and BBP)were detected in indoor and outdoor dust of Changchun City.The total concentrations of 9PAEs in indoor and outdoor dust ranged from 209.2 to 702.3 mg·kg-1 and 98.6 to323.6 mg·kg-1,with the average values of 208.5 mg·kg-1 and 166.1 mg·kg-1.Among them,DEHP was the most abundant phthalate with the content of 96.5 mg·kg-1 and208.5 mg·kg-1,respectively.The concentrations of 9 PAEs in outdoor dust were lower than those in indoor dust.Compared with other cities and regions all over the world,the PAEs contamination in Changchun is at a medium level.(2)A 14-day developmental exposure test was designed with medaka embryos as experimental subjects.The mortality rate,hatching rate and deformity rate of medaka were observed and evaluated;the aberrations of medaka embryos during embryonic development were observed and analyzed by microscope;the gene and enzyme activities of juvenile fish hatched under combined exposure conditions were detected to reveal the combined toxic effects of combined pollution of heavy metals and phthalates.The results showed that the combined pollution of Cd and DEHP had a series of adverse effects on the development of medaka embryos,including hatching inhibition,mortality increase and heart rate decrease and a variety of teratogenesis,among which pericardial cyst and spinal deformity were the most common distortion.Combined pollution of Cd and DEHP caused oxidative stress in medaka,disrupted the original redox balance in medaka,and induced more antioxidant enzymes(SOD,CAT and POD)in medaka embryos.The increase of malondialdehyde(MDA)content further indicated the oxidative damage to the body.Combined pollution of Cd and DEHP can cause developmental toxicity to medaka embryos by affecting the expression of HSP70 and the bone development abnormality by up regulating the expression of BMP2 and BMP4.Combined pollution of Cd and DEHP can also induce cardiac malformation by interfering with the expression of CYP1A,NKX2.5 and FGf8,which reveals the mechanism of early embryonic cardiac development damage.(3)The 28-day exposure test was designed to reveal the toxic effect and mechanism of Cd and DEHP pollution on the adult fish from the aspects of morphological change,oxidative stress,gene expression and metabology.The main conclusions are as follows:treatment group of single Cd10?g·L-1,Cd10?g·L-1+DEHP20?g·L-1,and Cd10?g·L-1+DEHP 200?g·L-1 increased the bone deformity rate and mortality of medaka with the exposure time.The cumulative bone deformity rate of the three treatment groups reached 7.5%,10%,12.5%on the28th day of exposure,and the cumulative mortality rate was 7.5%,12.5%,15%,22.5%respectively.The combined pollution of Cd and DEHP caused oxidative stress in the body of medaka.In the early stage of exposure,it induced the fish to produce more antioxidant enzymes(SOD,CAT and POD)to fight the free radicals produced by oxidative damage.With the exposure time extended,the activity of antioxidant enzymes decreased.MDA content showed a gradual increase with the exposure time,which further explained the oxidative damage to the body.The results of fluorescence quantitative PCR showed that Cd and DEHP combined pollution induced bone development abnormality and distortion by inducing up regulation genes BMP2 and BMP4 expression.The single Cd pollution,Cd and DEHP combined pollution caused the changes of metabolites in the medaka,which mainly affected the lipid metabolism,followed by amino acid metabolism.(4)The health risk index of heavy metals in indoor and outdoor dust in Changchun City did not exceed the reference value,indicating that dust heavy metals did not pose health risk to the exposed population;however,the maximum value of the total hazard index(HI)of phthalates ingested by children through exposure to indoor dust exceeded 1,and 4%of the indoor dust samples exceeded the critical value of HI,indicating that phthalates are harmful to children.The risk of phthalates to children can not be ignored.The uncertainty of health risk assessment posed by Cd and DEHP was analyzed combining with the toxicology experiment of medaka.At present,there is no unified standard and reference method for health risk assessment under the joint action of multiple pollutants.Instead,only health risk assessment posed by one kind of pollutant is considered,which will make the health risk underestimated or overestimated.Therefore,the results of health risk assessment have certain uncertainty,so it is necessary to establish an evaluation standard for the combined action of multiple pollutants. |
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