Occurrence characterization of fluorinated liquid crystal monomers in indoor dust and human health exposure risks

Fluorinated liquid crystal monomers （FLCMs） are the most widely used materials in liquid crystal display （LCD） manufacturing. They can be released into environmental media during production， use， and disposal， and are recognized as a class of novel persistent organic pollutants. Contamination of FLCMs in indoor dust is closely linked to human health； however， existing research has yet to fully elucidate their occurrence characteristics and population-differentiated health risks within this medium. This study analyzed the occurrence characteristics of FLCMs in dust from five indoor environments （laboratories， dormitories， classrooms， print shops， and cafeterias） using comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry （GC×GC-TOF MS）. Population-differentiated health risks were further evaluated by Monte Carlo simulation. The results showed that the total contents of 20 target FLCMs ranged from 3.68 to 593 ng/g （median： 85.1 ng/g）. Print shops exhibited the highest ∑FLCMs contents （206-593 ng/g）， followed by laboratories （89.0-219 ng/g） and classrooms （28.4–137 ng/g）. This differential distribution was closely associated with the number and types of electronic devices， ventilation conditions， and indoor cleaning frequency. The health risk assessment indicated that 4-［difluoro（3，4，5-trifluorophenoxy）methyl］-3，5-difluoro-4′-propylbiphenyl （tFPO-CF2-dF3B）， and 4-［trans-4-（trans-4-ethylcyclohexyl）cyclohexyl］-1-trifluoromethoxybenzene （2bcHtFMeOP） pose a higher health risk （hazard quotient （HQ）>1.00×10-6） than the other FLCMs， which is probably result of their higher fugitive contents as well as higher autotoxicity. Print stores had the highest hazard index （HI） for all age groups （median HI range： 1.88×10-5-1.60×10-4）， which was 2-6 times higher than other sites. Population difference analysis reveals that minors （especially infants and young children） are more sensitive to indoor dust FLCMs exposure， which may be due to the high exposure rate of infants and young children caused by their crawling， playing， and hand mouth contact on the ground. In addition， the results indicate that the estimated daily intakes （EDIs） of elderly people （>60 years old） is higher than that of the 18-45 and 45-60 age groups， which may be related to their longer indoor exposure time and lower cleaning frequency due to their limited mobility. It is worth noting that in the college environment group （18-45 years old）， although the exposure risk in this age group is lower than that of the sensitive population mentioned above， the related health risks cannot be ignored. In addition， it was found that the exposure risk of women in this group was slightly higher than that of men， which may be because women usually spend more time indoors and have a higher frequency of exposure. This study fills the gaps in the occurrence characteristics of FLCMs in indoor dust and population differentiated health risk assessment， providing comprehensive and detailed data support for the control and management of FLCMs pollution.