| Due to their widespread pollution sources,metal contaminants are easily found in various environmental media,exhibiting characteristics such as difficulty in biodegradation,undemanding bioaccumulation,and potential significant hazards.As a result,metal pollution has become a globally recognized environmental issue,with its associated environmental health problem garnering widespread attention from scholars worldwide.Environmental metals can enter the human body through multiple media and pathways.Previous studies have focused on exposure assessments and health risk evaluations for a single environmental medium or exposure pathway,failing to comprehensively reflect the real exposure and health risks of metals,and properly evaluate the contributions of different exposure media and pathways.Research on total environmental exposure can address these shortcomings while further identifying the influencing factors of total exposure,providing important foundational data and scientific basis for government agencies to establish environmental health standards based on multi-media pollutant exposure and clarify pollution prevention and control priorities.In this study,we conducted a combined questionnaire survey and follow-up monitoring approach to investigate the total environmental exposure characteristics of3,855 participants in Taiyuan,Dalian,Shanghai,Wuhan,Chengdu,and Lanzhou.The exposure parameters,environmental exposure behavior patterns,and exposure levels in air,drinking water,soil/dust,and diet had been obtained.Redundancy analysis was employed to identify the major factors and their influence strength basing on the total human environmental exposure characterizes.Using the main influencing factors as input parameters,a metal total environmental exposure assessment model was constructed through the random forest method.Finally,utilizing a health risk assessment model,we evaluated the spatiotemporal heterogeneity and population differences in non-carcinogenic and carcinogenic risks caused by multi-media and multi-pathway exposures among the surveyed population.We analyzed the contributions of different exposure media and pathways to population health risks and identified the priorities for metal element prevention and control based on bioavailability levels and health risks.The study yielded several meaningful findings as follows:（1）Total environmental exposure characteristics of the surveyed population in typical areas:average height,weight,skin surface area,long-term respiratory volume,dietary intake,and water intake were 165.51 cm,62.43 kg,1.65 m2,13.38 m3/d,1053.69g/d,and 1.43 L/d,respectively.Indoor time,outdoor time,transportation time,and household ventilation time were 19.47 h/d,3.65 h/d,64.61 min/d,and 335.16 min/d,respectively.Comprehensive exposure coefficients for indoor air,outdoor air,transportation air,drinking water,water use,soil/dust dermal contact,soil/dust ingestion,soil/dust inhalation,and dietary exposure were 0.1740 m3/（kg·d）,0.0328m3/（kg·d）,0.0097 m3/（kg·d）,0.0235 L/（kg·d）,0.0033 m2/（kg·d）,0.0013 m2/（kg·d）,0.8207 mg/（kg·d）,0.2147 m3/（kg·d）,and 17.25 g/（kg·d）,respectively.（2）The total environmental exposure levels of different metals among the surveyed residents varied,with differences in gender,age,urban-rural areas,and regions.The exposure levels of metals in the surveyed residents were,in descending order,As>Pb>Hg>Cd,ranging from 3.78×10-3 to 2.74×10-3 mg/（kg·d）,1.16×10-4to 1.60×10-4 mg/（kg·d）,1.75×10-5 to 1.85×10-5 mg/（kg·d）,and 2.16×10-5 to 1.96×10-5mg/（kg·d）,respectively.Generally,females had higher exposure levels than males,and the 18-44 age group exhibited higher metal total environmental exposure levels.For non-heating periods,As and Pb exposure levels were higher in urban areas compared to rural areas,while heating period Cd exposure levels followed the same pattern.Dalian residents had relatively higher total environmental exposure levels to Hg and As,while Chengdu residents had higher exposure levels to Cd and Pb.（3）The human total environmental exposure levels were significantly influenced by exposure activity patterns,and the constructed model of total environmental exposure to metal demonstrated good accuracy.There were seasonal differences in the influencing factors of human total environmental exposure to metals.The five major factors in non-heating seasons were water usage type,handwashing habits,total food intake,presence of industrial enterprises,and ground type.In contrast,the five major factors during the heating season were heating methods,presence of industrial enterprises,handwashing habits,water heating utensils,and water usage type.Residents with higher total environmental exposure levels were those living near industrial activities,using ceramic pots for heating water,drinking well water,using soil heating and wood stoves,and having carpets or soil as ground types.Moreover,human total environmental exposure levels increased with dietary intake,heating duration,outdoor activity time,and travel time.The constructed total environmental exposure assessment model had been validated to have good reliability and accuracy.（4）Health risk assessments based on total human environmental exposure revealed that,with the exception of As,exposure to Hg,Cd,and Pb in typical regions did not pose health risks to the surveyed population.The health risk assessment results were validated as reliable.Health risks associated with total environmental exposure to metals in the surveyed population exhibited differences in gender,age,urban-rural areas,and regions.The hazard index（HI）and total cancer risk（TCR）values for As exposure were bigger than 1 and 10-4,respectively,posing potential non-carcinogenic and carcinogenic risks.Dietary exposure to Hg,As,and Pb through the digestion was the primary pathway for Hg,As,and Pb health risks,while inhalation of Cd in the air was the main pathway for Cd non-carcinogenic and carcinogenic risks.The multi-media,multi-pathway health risk assessment from metal exposure was validated as reliable and accurately reflected the health risks of the surveyed population based on total environmental exposure to metals.（5）Investigating the characteristics of total environmental metal exposure can provide a scientific basis for the development of precise policies and measures for metal pollution prevention and control.There were significant differences in the priority order of metal occurrence levels and the health risks associated with total environmental exposure,and the highest priority for control was given to environmental Pb and As,respectively.The study revealed that dietary exposure through the digestion was the preferred pathway for the priority control of health risks associated with Hg,As,and Pb,with combustion and industrial sources being the main control sources.On the other hand,airborne exposure through the inhalation was the preferred path for the priority control of health risks associated with Cd,with traffic sources being the main control source for indoor air and industrial sources for outdoor air.In summary,there are significant spatiotemporal,gender,and age differences in the total human environmental exposure to metals in China.These disparities are influenced by factors such as water type,handwashing habits,total food intake,and the presence of industrial enterprises.The total environmental exposure assessment model,built based on the influencing factors of total human environmental exposure to metals,can be utilized as a substitute for traditional environmental exposure research methods.The total human environmental exposure to As may pose potential non-carcinogenic and carcinogenic risks to human health.By conducting health risk assessments based on total environmental exposure to metals,we can achieve precise prevention and control measures against environmental metal exposure in a targeted and locally adapted manner. |
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