Independent risk evaluation associated with short-term black carbon exposure on mortality in two megacities of Yangtze River Delta, China.

The adverse health effects of PM2.5 have been well demonstrated by many studies. However, as a component of PM2.5, evidence on the mortality risk of black carbon (BC) is still limited. In this study, based on the data of daily mean PM2.5 concentration, BC concentration, meteorological factors, total non-accidental (all-cause) and cardiovascular mortality in Shanghai and Nanjing during 2015-2016, a semi-parameter generalized additive model (GAM) in the time series and the constituent residual approach were employed to explore the exposure-response relationship between BC and human mortality in these two megacities of Yangtze River Delta, China. The main objective was to separate the health effects of BC from total PM2.5, and compare the difference of mortality ER related to BC original concentration and adjusted concentration after controlling PM2.5. Results showed that there were all significantly associated with daily mortality for PM2.5 and BC. The percentage excess risk (ER) increases in all-cause and cardiovascular categories were 1.68 % (95 % s 1.28, 2.08) and 2.16 % (95 % CI: 1.54, 2.79) with 1 µg/m3 increment in original BC concentration in Shanghai. And the ER in Nanjing was smaller than that in Shanghai. After eliminating PM2.5 confounding effects by a constituent residual approach, the BC residual concentration still had a strong significant ER. The ER for BC residual in Shanghai got an obvious increase, and ER of the cardiovascular mortality for all, females and males increased by 0.55 %, 1.46 % and 0.62 %, respectively, while the ER in Nanjing decreased slightly. It also revealed that females were more sensitive to the health risk associated with short-term BC exposure than males. Our findings provide additional important evidence and ER for mortality related to independent BC exposure. Therefore, BC emission reduction should be paid more attention in air pollution control strategies to reduce BC-related health burdens.

Prevalence and multilocus sequence typing of Clostridium perfringens isolated from retail chicken products and diseased chickens in Tai'an region, China.

BACKGROUND: Clostridium perfringens is an important zoonotic microorganism, which can cause diseases in animals and humans under suitable conditions. Contamination of C. perfringens in chicken products has been reported worldwide, but the genetic diversity and relationship of isolates were seldom analyzed. OBJECTIVES: The current study was undertaken to investigate the prevalence of C. perfringens from retail chicken products and sick chickens with suspected necrotic enteritis (NE) in Tai'an area, China. METHODS: In total, 295 samples were collected from Tai'an large poultry retail market and veterinary hospital in 2018, then the isolates were tested for toxin genes, drug resistance and multilocus sequence typing (MLST). RESULTS: Overall, 138 (46.78%) samples were determined to be positive for C. perfringens, and 99.37% of the isolates were identified as C. perfringens type A, with the remaining isolates being type F; 18.99% of the isolates were positive for cpb2 gene. Antimicrobial susceptibility testing revealed that 52.27% of the isolates from poultry retail market and diseased chickens showed multiple antibiotic resistance. MLST results showed that 50 analyzed isolates can be divided into 39 sequences types (STs), clustered in three clonal complexes (CCs) and 23 singletons. Although most of the isolates belong to type A, considerable genetic diversity can be observed, with the Simpson's diversity index up to 0.9181. MLST results and phylogenetic analysis showed that a portion of the isolates from humans and chickens were assigned to the same clusters in the phylogenetic tree or found to be in the same CCs, indicating the chicken isolates and the human isolates are related in certain stratification. CONCLUSIONS: This study showed that the contamination rate of C. perfringens in the local retail chicken products was relatively high. Most of the isolates exhibit broad-spectrum antimicrobial resistance. The high antibiotic resistance of C. perfringens isolates and the relationship between isolates from human and chicken indicated potential public health risks.