Social cost of mining-related lead (Pb) pollution in Kabwe, Zambia, and potential remediation measures

Prevalence of mental distress in adults with and without a history of tuberculosis in an urban Zambian community

People with tuberculosis (TB) are susceptible to mental distress. Mental distress can be driven by biological and socio-economic factors including poverty. These factors can persist beyond TB treatment completion yet there is minimal evidence about the mental health of TB survivors. A cross-sectional TB prevalence survey of adults was conducted in an urban community in Zambia. Survey participants were administered the five-item Self Reporting Questionnaire (SRQ-5) mental health screening tool to measure mental distress. Associations between primary exposure (history of TB) and other co-variates with mental distress were investigated using logistic regression. Of 3,393 study participants, 120 were TB survivors (3.5%). The overall prevalence of mental distress (SRQ-5 ≥ 4) in the whole study population was 16.9% (95% CI 15.6%-18.1%). Previous TB history was not associated with mental distress (OR 1.20, 95% CI 0.75-1.92, p-value 1.66). Mental distress was associated with being female (OR 1.23 95% CI 1.00-1.51), older age (OR 1.71 95% CI 1.09-2.68) and alcohol abuse (OR 1.81 95% CI 1.19-2.76). Our findings show no association between a previous TB history and mental distress. However, approximately one in six people in the study population screened positive for mental distress.

Breeding, Biosorption Characteristics, and Mechanism of a Lead-Resistant Strain

To effectively carry out the bioremediation of a Pb²⁺ polluted environment, a lead-tolerant strain named D1 was screened from the activated sludge of a factory in Hefei, and its lead removal in a solution with Pb²⁺ concentration of 200 mg/L could reach 91% under optimal culture conditions. Morphological observation and 16S rRNA gene sequencing were used to identify D1 accurately, and its cultural characteristics and lead removal mechanism were also preliminarily studied. The results showed that the D1 strain was preliminarily identified as the Sphingobacterium mizutaii strain. The experiments conducted via orthogonal test showed that the optimal conditions for the growth of strain D1 were pH 7, inoculum volume 6%, 35 °C, and rotational speed 150 r/min. According to the results of scanning electron microscopy and energy spectrum analysis before and after the D1 exposure to lead, it is believed that the lead removal mechanism of D1 is surface adsorption. The Fourier transform infrared spectroscopy (FTIR) results revealed that multiple functional groups on the surface of the bacterial cells are involved in the Pb adsorption process. In conclusion, the D1 strain has excellent application prospects in the bioremediation of lead-contaminated environments.