Changli Tu

BACKGROUND: To illustrate the extent of transmission, identify affecting risk factors and estimate epidemiological modeling parameters of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in household setting. METHODS: We enrolled 35 confirmed index cases and their 148 household contacts, January 2020-February 2020, in Zhuhai, China. All participants were interviewed and asked to complete questionnaires. Household contacts were then prospectively followed active symptom monitoring through the 21-day period and nasopharyngeal and/or oropharyngeal swabs were collected at 3-7 days intervals. Epidemiological, demographic, and clinical data (when available) were collected. RESULTS: Assuming that all these secondary cases were infected by their index cases, the second infection rate in household context is 32.4% (95% confidence interval [CI]: 22.4%-44.4%), with 10.4% of secondary cases being asymptomatic. Multivariate analysis showed that household contacts with underlying medical conditions, a history of direct exposure to Wuhan and its surrounding areas, and shared vehicle with an index patient were associated with higher susceptibility. Household members without protective measures after illness onset of the index patient seem to increase the risk for SARS-CoV-2 infection. The median incubation period and serial interval within household were estimated to be 4.3 days (95% CI: 3.4-5.3 days) and 5.1 days (95% CI: 4.3-6.2 days), respectively. CONCLUSION: Early isolation of patients with coronavirus disease 2019 and prioritizing rapid contact investigation, followed by active symptom monitoring and periodic laboratory evaluation, should be initiated immediately after confirming patients to address the underlying determinants driving the continuing pandemic.

Microplastics (MPs) are abundant in air, but evidence of their deposition in the respiratory tract is limited. We conducted a prospective case series to investigate the deposition of microplastics in bronchoalveolar lavage fluid (BALF) and determine the internal dose of MPs via inhalation. Eighteen never-smokers aged 32-74 years who underwent fiberoptic bronchoscopy with BALF were recruited from Zhuhai, China. Control samples were obtained by performing the same procedure using isotonic saline instead of BALF. Laser direct infrared spectroscopy combined with scanning electron microscopy detected the presence and characteristics of MPs and quantitatively analyzed the microplastic in BALF and control samples. Concentrations of total and specific MPs in BALF and control samples were compared using the Wilcox test. Thirteen types of MPs were observed in 18 BALF samples. Polyethylene (PE, 86.1%) was the most abundant in BALF, followed by poly(ethylene terephthalate) (PET, 7.5%) and polypropylene (PP, 1.9%). Compared with the control samples, BALF had significantly higher concentrations of PE (median [IQR] of BALF: 0.38 [8.05] N/g), PET (0.26 [0.54] N/g), polyurethane (0.16 [0.24] N/g), PP (0.16 [0.11] N/g), and total MPs (0.91 [6.58] N/g). The presence of MPs in BALF provides novel evidence that MPs penetrate deep into the respiratory tract.

To investigate the relation of smoking and microplastic inhalation, we conducted a prospective study combining population-based and experimental work. Bronchoalveolar lavage fluid (BALF) samples from 17 smokers and 15 nonsmokers were collected in Zhuhai City, China. We simulated an active smoking model to explore the contribution of smoking to inhaled microplastics. The characteristics of microplastics in BALF samples and cigarette smoke were determined using laser direct infrared spectroscopy. We compared the differences between smokers and nonsmokers as well as between cigarette smoke and control groups. Microplastics were identified positive in all BALF samples. Smokers had higher concentrations of total microplastics (25.86 particles/g), polyurethane (11.34 particles/g), and silicone (1.15 particles/g) than nonsmokers. In the cigarette smoking simulation model, higher concentrations of total microplastics (9.99 particles/L), polyurethane (4.66 particles/L), and silicone (2.78 particles/L) were present in the cigarette smoke than those in the control group. We confirmed and extended the evidence on the presence of microplastics in the lower respiratory tract. These findings also provide new evidence on the relation between cigarette smoking and microplastic inhalation.

Microplastics (MPs) have received a lot of attention and have been detected in multiple environmental matrices as a new environmental hazard, but studies on human internal exposure to MPs are limited. Here, we collected lung tissue samples from 12 nonsmoking patients to evaluate the characteristics of MPs in human lung tissues using an Agilent 8700 laser infrared imaging spectrometer and scanning electron microscopy. We detected 108 MPs covering 12 types in the lung tissue samples, with a median concentration of 2.19 particles/g. Most of the MPs (88.89%) were sized between 20 to 100 μm. Polypropylene accounts for 34.26% of the MPs in the lung tissues, followed by polyethylene terephthalate (21.30%) and polystyrene (8.33%). Compared with males and those living far from a major road (≥300 m), females and those living near the main road (<300 m) had higher levels of MPs in lung tissues, which positively correlated with platelet (PLT), thrombocytocrit, fibrinogen (FIB), and negatively related with direct bilirubin (DB). These findings help confirm the presence in the respiratory system and suggest the potential sources and health effects of inhaled MPs.