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Air pollution exposure depends not only on outdoor but also on indoor air quality and human activities. The outbreak of coronavirus in 2019 occurred close to the Spring Festival in China, when many rural-to-urban workers moved to their hometowns, resulting in increased household (HH) consumption of solid fuels for space heating in the rural north. In this study, field measurements of HH PM2.5 (particulate matter with an aerodynamic size ⩽2.5 μm) from a rural village were performed to evaluate changes in indoor, outdoor, and total exposure during the quarantine. Both indoor and outdoor PM2.5 were, as expected, higher during the heating period than during the non-heating period, resulting in much more exposure during the heating season. Indoor exposure accounted for up to 87% and 95% of the total PM2.5 exposure during the non-heating and heating periods, respectively. The contributions of indoor exposure associated with internal sources were 46% and 66%, respectively. Indoor coal combustion resulted in an increment of about 62 ± 12 μg m−3 in indoor PM2.5 exposure. Due to the quarantine, the indoor-originated PM2.5 exposure increased by 4 μg m−3 compared to that during the heating period before the lockdown. In comparison with the exposure before the quarantine during the heating period, the outdoor exposure decreased by 5 μg m−3 during the quarantine, which was mainly attributable to much less time spent outdoors, although the outdoor PM2.5 levels increased from 86 ± 49 μg m−3 to 104 ± 85 μg m−3. However, the overall exposure increased by 13 μg m−3 during the quarantine, resulting from the changes in outdoor exposure (−5 μg m−3), outdoor-originated indoor PM2.5 exposure (+9 μg m−3), PM2.5 from indoor sources before the quarantine (+5 μg m−3), and quarantine-induced indoor PM2.5 increments (+4 μg m−3). The increase in air pollution exposure during quarantine deepened concerns about the issue of HH air pollution and the clean HH energy transition actions required to eliminate traditional solid fuels.

Based on STC8A8K64S4A12 microcontroller and LabVIEW[1] software, the two-axis translation stage control system is designed. The two-axis translation stage is applied to a plane plotter, and the two rails are placed at right angles to form a horizontal motion mechanism. The two-axis controller consists of STC8A8K64S4A12 microcontroller control board and TMC5160 stepper motor driver[2], which realizes independent control of the two-axis translation stage. At the same time, PC software is designed, which can be connected to the two-axis controller through network interface or serial communication interface. The two-axis translation stage is controlled by a PC or a laptop. Repeated test experiments were carried out on the system. The experimental results show that the system has high reliability and control precision, and the horizontal displacement control accuracy is 0.01 mm.

Recent studies in different localities in Nigeria report high concentrations of airborne polycyclic aromatic hydrocarbons (PAHs) –a group of ubiquitous hazardous chemicals produced by incomplete combustion or pyrolysis processes. Inhalation exposure to PAHs has been shown to elicit both cancer and non-cancer adverse effects. Yet, there is currently no national guideline for regulating exposure to airborne PAHs in Nigeria. In this study, we developed national health-based target for 16 priority PAHs using literature information on the toxicity of the PAHs, the baseline severities of the diseases in Nigeria and the population demography. We developed ourhealth-based target (ng/m3) from 10cancers and 34 non-cancer adverse health outcomes linked to PAH exposure. Our proposed limits for the PAHs ranged from 0.02 ng/m3 for dibenzo[a,h]anthracene to 1.0 ng/m3 for benzo[g,h,i]perylene – the most or least toxic PAH, respectively. On the basis ofbenzo[a]pyrene equivalent concentration, ournational PAH limit of 0.15 ng/m3is however less stringent than the global PAH limit of 0.12 ng/m3.