Methylsiloxanes (MSs) are a significant source of indoor environmental pollution due to their high production level and widespread application, and pose a potential health risk. Given the special vulnerability of children to environmental contaminants, assessment of indoor MSs exposure in children is quite essential. In this study, we assessed internal exposure doses and external exposure levels of MSs in children from industrial and residential areas in southwestern China. Indoor air, indoor dust, and personal care product (PCP) samples were collected to evaluate indoor non-dietary MSs exposure in children through various pathways. The concentrations of MSs in indoor environments of industrial areas were approximately one to four orders of magnitude higher than those of residential areas. Sun protection products contained the highest concentrations of MSs. Relatively high levels of cyclic methylsiloxanes (CMSs) were found in plasma of children from industrial areas, which were one to two orders of magnitude higher than those in children from residential areas. The highest MSs levels in plasma were detected in infants (0–1 year), with values of 1.4 × 102 ng/mL and 1.3 × 102 ng/mL for CMSs (D4–D6) and linear methylsiloxanes (LMSs) (L5–L16), respectively. The internal exposure dose of infants in residential areas is driven by major unknown sources of MSs. The average daily doses via inhalation and dust ingestion in children from industrial areas were one to three orders of magnitude higher than in those from residential areas, indicating that these children should be considered a highly exposed population. Inhalation and dust ingestion were both major exposure pathways to MSs for children of all age groups in industrial areas, whereas dermal absorption from PCPs was the predominant exposure pathway for children of all age groups in residential areas (except for infants). Although the exposure risk to D4 and D5 was at an acceptable level for all children studied, the total daily exposure doses of these two cyclic compounds via inhalation for infants in the industrial areas was near the chronic reference dose. Meanwhile, MSs may accumulate in infant plasma within a short period of time (<6 months). Therefore, infants should be the focus of greater attention in future research. As indoor environments may pose high risks for infants in industrial areas, they should be the focus of future research. © 2021

Peroxyacetyl nitrate (PAN) is the most important reservoir of nitrogen oxides, with effects on atmospheric oxidation capacity and regional nitrogen distribution. The first yearlong observational study of PAN was conducted from September 2018 to August 2019 at a suburban site and an urban site in Zhengzhou, Henan Province, central China. Compared with studies over the past two decades, summer PAN pollution at the suburban site and winter PAN pollution at both sites were more significant, with annual average concentrations of 1.96 ± 1.44 and 2.01 ± 1.59 ppbv, respectively. Seasonal PAN discrepancies between the urban and suburban areas were analyzed in detail. Active PAN formation, regional transport, photochemical precursors, and PAN lifetime played key roles during seasons with elevated PAN (winter and spring). According to the results of cluster analysis and potential source contribution function analysis, during the cold months, short-distance air mass transport from the east, south, and southeast of Henan Province and southern Hebei Province increased PAN pollution in urban Zhengzhou. PAN source areas were located in circumjacent industrial cities surrounding Zhengzhou except in the northeastern direction. Based on the relationships between pollutant concentrations, wind speed, and wind direction, a strong positive correlation between PAN and PM2.5 (and O3) existed in winter due to their joint transport. A slow-moving, low-height air mass passed through surrounding industrial cities before reaching the study area, carrying both pollutants and leading to strong consistency between PAN and O3 levels. The long-term PAN characteristics described in this study will help clarify the causes of regional air pollution in inland city agglomerations. Moreover, the PAN correlations and joint transport of PAN and PM2.5 (or O3) support the use of PAN as an indicator of air pollution introduced from surrounding industrial areas. © 2021 Elsevier B.V.

Neonicotinoid insecticides (NEOs) have attracted particular attention in recent years due to their wide occurrence and potential impacts on the ecosystem and human health. This study aimed to compare the composition and level of NEOs in soils of different land use types. Two rounds of sampling were performed in Tianjin, China, with 158 soil samples in fall and 61 soil samples in spring collected from five types of land, i.e., greenhouse, orchard, farm, park and residential area. The concentrations of eight NEOs, i.e., imidacloprid (IMI), acetamiprid (ACE), thiamethoxam (THX), clothianidin (CLO), thiacloprid (THA), dinotefuran (DIN), nitenpyram (NIT) and flonicamid (FLO), were analyzed in the soil samples using LC-MS/MS. Six NEOs were detected, with IMI, ACE and THX being the most frequently detected ones. Concentrations of NEOs (arithmetic means in fall and spring, respectively) in greenhouse were the highest (2.52×102 and 4.59×102 ng g−1), followed by in orchard (35.1 and 1.31×102 ng g−1), park (50.4 and 1.02×102 ng g−1), residential area (20.2 and 1.38×102 ng g−1) and farm (25.5 and 84.2 ng g−1). The contribution of individual NEO varied in soils of different land use types. Both IMI and THX were largely used in greenhouse, while IMI was the main NEO in the other four lands. The NEO levels in soils planted with different crops varied greatly. Extremely high levels of NEOs (>103 ng g−1) were observed in soils planted with watermelon, tomato and peach in greenhouse. The ubiquitous presence of NEOs in soils deserves more attention, particularly in greenhouse. © 2021 Elsevier B.V.