Microbiological quality assessment of fresh produce: Potential health risk to children and urgent need for improved food safety in school feeding schemes

About 388 million school-going children worldwide benefit from school feeding schemes, which make use of fresh produce to prepare meals. Fresh produce including leafy greens and other vegetables were served at 37% and 31% of school feeding programs, respectively, in Africa. This study aimed at assessing the microbiological quality of fresh produce grown onsite or supplied to South African schools that are part of the national school feeding programs that benefit over 9 million school-going children. Coliforms, Escherichia coli, Enterobacteriaceae, and Staphylococcus aureus were enumerated from fresh produce (n = 321) samples. The occurrence of E. coli, Listeria monocytogenes, Salmonella spp., and extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae was determined. Presumptive pathogens were tested for antimicrobial resistance. E. coli was further tested for diarrheagenic virulence genes. Enterobacteriaceae on 62.5% of fresh produce samples (200/321) exceeded previous microbiological guidelines for ready-to-eat food, while 86% (276/321 samples) and 31.6% (101/321 samples) exceeded coliform and E. coli criteria, respectively. A total of 76 Enterobacteriaceae were isolated from fresh produce including E. coli (n = 43), Enterobacter spp. (n = 15), and Klebsiella spp. (n = 18). Extended-spectrum β-lactamase production was confirmed in 11 E. coli, 13 Enterobacter spp., and 17 Klebsiella spp. isolates. No diarrheagenic virulence genes were detected in E. coli isolates. However, multidrug resistance (MDR) was found in 60.5% (26/43) of the E. coli isolates, while all (100%; n = 41) of the confirmed ESBL and AmpC Enterobacteriaceae showed MDR. Our study indicates the reality of the potential health risk that contaminated fresh produce may pose to school-going children, especially with the growing food safety challenges and antimicrobial resistance crisis globally. This also shows that improved food safety approaches to prevent foodborne illness and the spread of foodborne pathogens through the food served by school feeding schemes are necessary.

Occurrence and Health-Risk Assessment of Trace Metals in Geothermal Springs within Soutpansberg, Limpopo Province, South Africa

Geothermal springs are natural geological phenomena that occur throughout the world. South Africa is blessed with several springs of this nature. Limpopo province contains 31% of all geothermal springs in the country. The springs are classified according to the residing mountain: Soutpansberg, Waterberg and Drakensberg. This study focused on the geothermal springs within the Soutpansberg region; that is, Mphephu, Siloam, Sagole and Tshipise. The study was aimed at assessing the occurrence and potential health risk associated with drinking water from geothermal springs within Soutpansberg. Geothermal springs and boreholes were sampled for a period of 12 months (May 2017-May 2018) to accommodate two major seasons in the study areas. The physicochemical and trace metal compositions of the geothermal springs and boreholes (tepid and hot) were analyzed using ion chromatography (IC) (Dionex Model DX 500) and inductively coupled plasma-mass spectrometer (ICP-MS). Trace metal concentrations of the geothermal springs and boreholes were within permissible drinking water guidelines by the South African National Standards (SANS) and World Health Organisation (WHO), with exception of mercury (Hg), which is high in summer season. The bioaccumulation from regular consumption could, however, result in negative effects. Pearson's correlation revealed that there is a direct relationship between temperature and pH, and some of the trace metals (V, Zn, Hg, Pb). This implies dissolution of minerals (rock-water interaction) under slightly high temperature. Multivariate statistics further elucidate the relationship and possible sources of the trace metals. Therefore, it can be inferred that the rock-water interaction is the main geochemical process governing the release of trace metals in groundwater. Hazard Index values for both children and adults were higher than 1, and this implies that the communities are at high risk of non-cancer health effects. Further, As, Cr and Cd were found to be the highest contributors to the potential cancer risk in the study areas, with children having a higher risk than adults. Therefore, there is a need for clinical/epidemiological study, and regular monitoring and control measures, to verify actual prevalence of cancer and protect human health, particularly the children, within the study areas.

Thallium in color tattoo inks: risk associated with tattooing

BACKGROUND

Allergic reactions to metals and metal salts used in tattoo pigments occur surprisingly frequently. For this reason, this study focused on the determination of thallium (Tl) in the samples of color tattoo inks. These inks are commonly used in tattooing processes worldwide.

MATERIAL AND METHODS

The samples were analyzed with the use of differential pulse anodic stripping voltammetry. The stripping anodic peak current of Tl was linear over its concentration range of 0.5-6.0 μg/l, which corresponds to 2.45×10^-9-2.94×10^-8 M. The determined value of the limit of detection (LOD) was equal to 0.149 μg/l (7.29×10^-10 M).

RESULTS

The obtained results revealed a wide range of Tl contents in tattoo inks, i.e., 0.0029-0.4275 μg/g. The content of this metal varied substantially depending on the pigment used in tattoo inks.

CONCLUSIONS

Thallium was identified and determined in all tested samples. Its content depends on the country of origin but it does not depend directly on the color. The lowest content of Tl was found in the pink ink and the highest in the violet ink (from Israel), and a similar content was also found in the yellow ink (from Israel). The use of colored inks in larger quantities (a dense pattern and a larger surface area covered) may potentially pose a health risk. The danger of Tl poisoning from tattooing depends on the type of the ink (color) and its origin. As Tl is not considered a micronutrient, introducing such a Tl content into the body may be associated with a potentially harmful accumulation of this metal in body organs, causing various types of ailments and toxic effects primarily on the nervous, skeletal and circulatory systems. The obtained results suggest that tattooists may be exposed to the toxic effects of Tl in tattoo inks. The analytical data presented in the paper may constitute the basis for determining the acceptable limits of toxic Tl contents in tattoo inks. Med Pr. 2020;71(4):405-11.

Accumulation of Heavy Metals in Tea Leaves and Potential Health Risk Assessment: A Case Study from Puan County, Guizhou Province, China

This study features a survey of the concentrations of aluminum (Al) and heavy metals (Mn, Pb, Cd, Hg, As, Cr, Ni, Cu, and Zn) in tea leaves and the corresponding cultivation soils (0–30 cm), carried out in Puan County (Guizhou Province, China). The average concentrations of Al, Mn, Pb, Cd, Hg, As, Cr, Ni, Cu, and Zn in the soil were 106 × 10³, 214, 20.9, 0.09, 0.12, 17.5, 121, 27.8, 131.2, and 64 mg·kg⁻¹, respectively. The heavy metals’ pollution indexes in the soil can be ranked as follows: Cu > Cr > Hg > As > Ni > Zn > Pb > Mn > Cd. The soil was moderately polluted by Cu because of the high geochemical background value of Cu in the area. The potential environment risk index (RI) showed that 7.69% out of the total sample sites were within the moderate level. Moreover, the ranges of Al, Mn, Pb, Cd, Hg, As, Cr, Ni, Cu, and Zn concentrations in young tea leaves were 250–660, 194–1130, 0.107–0.400, 0.012–0.092, 0.014–0.085, 0.073–0.456, 0.33–1.26, 6.33–14.90, 14.90–26.10, and 35.8–50.3 mg·kg⁻¹, respectively. While in mature tea leaves, they were 4300–10,400, 536–4610, 0.560–1.265, 0.040–0.087, 0.043–0.089, 0.189–0.453, 0.69–2.91, 3.43–14.20, 6.17–16.25, and 9.1–20.0 mg·kg⁻¹, respectively. Furthermore, the concentrations of Pb, Cu, As, Hg, Cd, and Cr in young tea leaves and mature tea leaves were all lower than the standard limit values (5.0, 30, 2.0, 0.3, 1.0, and 5.0 mg·kg⁻¹ for Pb, Cu, As, Hg, Cd, and Cr, respectively) in China. Besides, the accumulation ability of tea leaves to Mn was the strongest, and the average bioconcentration factor (BCF) of Mn in mature tea leaves was 12.5. In addition, the average target hazard quotients (THQ) were all less than one for the young tea leaves and the average aggregate risk hazard index (HI) to adults was 0.272, indicating that there was not a potential health risk for adults through the consumption of the infusions brewed by young tea leaves. However, for mature tea leaves, the percentage which HI values were above one was 38.46%, and the risk to adults via the consumption of mature tea infusions were mainly contributed by Mn and Al.