Joshua O Olowoyo

Prof. Joshua O Olowoyo

Department of Biology, Sefako Makgatho Health Sciences University, Medunsa 0204, South Africa

Research Focus & Metrics

Academic Career Length

18Years (2009-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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14 January 2025 in Antibiotics
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OOOluwaseun Mary Oladeji
Oluwaseun Mary Oladeji
LMLiziwe Lizbeth Mugivhisa
Liziwe Lizbeth Mugivhisa
JOJoshua O Olowoyo
Joshua O Olowoyo
This review investigates the levels of antibiotic residues in animal products, types of antibiotics, and their possible impact on human health in Africa. The literature search involved the use of a systematic survey using data that were published from Africa from 2015 to 2024. The search terms used the Boolean operators with keywords such as antibiotics, antibiotic residues, antibiotics in animal products in Africa, and impact on human health. Only research conducted in Africa was used in the present study. The findings showed that the most prevalent groups of antibiotic residues were aminoglycoside, macrolides, β-lactams, fluoroquinolones, tetracyclines sulfonamides, and phenicols. Tetracycline showed the most prevalent antibiotic residue with 43% mostly from East Africa, followed by sulfonamides at 19%, and β-lactams at 16%; most of the antibiotic residue levels were higher than the World Health Organization permissible limit. Noncompliance with withdrawal periods and maximum residue limits for antibiotics used in food-producing animals may lead to negative outcomes such as allergic reactions, teratogenicity, carcinogenicity, microbiome alterations, and, most notably, antibiotic resistance. As a result, there is a need for constant monitoring of antibiotic residues in animal products in addition to the consideration of alternatives to antibiotics in order to avoid their health implications.

JOJoshua O Olowoyo
Joshua O Olowoyo
GLGladness Ntebo Lion
Gladness Ntebo Lion
UTUnathi Tshoni
Unathi Tshoni
OAOluwaseun Mary Areo
Oluwaseun Mary Areo
Leaded fuel has been reported to contain certain amounts of toxic trace metals such as Pb and Cadmium (Cd), which may have negative impacts on humans and the environment. Unleaded fuel was introduced to South Africa in 2006 with the aim of reducing and eventually eliminating the negative impact of leaded fuel on the environment. However, trace metals are usually nonbiodegradable, and it may therefore be necessary to monitor their presence in the environment so as to evaluate their possible impact on human health. The present study evaluated the levels of Pb and other heavy metals in soil samples collected from petrol (gas) filling stations and from busy roads just around the filling stations in Pretoria, South Africa, fifteen years after the introduction of unleaded fuel. A total of twenty-four (24) soil samples were analysed for lead (Pb), chromium (Cr), copper (Cu), zinc (Zn), arsenic (As), iron (Fe), manganese (Mn), nickel (Ni), titanium (Ti), and cadmium (Cd) using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The results showed that the concentrations of the trace metals were in the following ranges: Pb, 0.08 ± 0.02–188.36 ± 15.32 ug/g; Mn, 5.35 ± 0.34–6842.43 ± 1.35 ug/g; Zn, 1.82 ± 0.22–9814.89 ± 22.32 ug/g; As, 0.21 ± 0.00–8.42 ± 2.44 ug/g; Cu, 10.51 ± 3.41–859 ± 0.09 ug/g; Cr, 5.80 ± 2.21–417.70 ± 9.08 ug/g; Ti, 19.94 ± 4.99–1036.12 ± 1.49 ug/g; and Fe, 3.06 ± 7.87–674.07 ± 12.22 mg/g. The highest concentrations from all the elements were recorded for Fe in all the collected soil samples. The concentrations of Pb in the soils collected from sites associated with high traffic and industrial areas were higher than for those from all other sites, and the differences were significant (p < 0.05). The pollution index (PI), which is the anthropogenic influence of the trace metals, and the geoaccumulation (Igeo), which allows for the removal of possible variations as regards the studied element in the soil due to the possible differences in the background value, showed that some samples were enriched anthropogenically. The PI for Ni, Pb, Cu, and Cr indicated highly anthropogenically contaminated soils, especially at sites associated with high traffic volumes and in industrial areas. The Igeo showed moderately polluted areas for Pb and Cu in high-traffic areas. The exposure routes for the toxic trace metals that were of concern in the study were either through ingestion or dermal contact. The calculated hazard quotient showed both noncarcinogenic and carcinogenic risks for Fe and Mn via ingestion and through dermal contact for both children and adults, respectively. The concentrations of Pb were high and similar to those that were previously reported in the study and pointed to vehicular emission as one of the contributors. The study also noticed an increase in the presence of Mn and Fe in all soil samples.

16 June 2021 in Molecules
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Ovokeroye AbafeOvokeroye Abafe
Ovokeroye Abafe
LMLinda R Macheka
Linda R Macheka
JOJoshua O Olowoyo
Joshua O Olowoyo
An ultra-high performance liquid chromatography tandem mass spectrometry method was developed and validated for the sensitive determination and unambiguous confirmation of residues of per and polyfluorinated alkyl substances (PFAS) in breastmilk, retail milk and infant formulas following two sample preparation methods. Sample pre-treatment was carried out by a simplified QuEChERS method without requiring dSPE or any further clean-up. The method was validated in accordance with the requirements of Commission Decision 657/2002/EC with slight modifications. The method displayed good linearity with R2 ranging from 0.9843–0.9998 for all target PFAS. The recovery and within-laboratory reproducibility of the method (n = 63) were in the range 60–121% and 5–28%, respectively. The decision limit, detection capability and limit of quantitation ranged from 30–60 ng kg−1 to 40–100 ng kg−1 and 5–50 ng kg−1, respectively. Acceptable matrix effect values in the range −45–29% were obtained with uncertainty of measurement lower than 25% for all target PFAS. The method displays its suitability for the sensitive and high-throughput confirmatory analysis of C4–C14 PFAS in breastmilk, dairy milk and infant formulas.

JOJoshua O Olowoyo
Joshua O Olowoyo
LMLinda R Macheka
Linda R Macheka
Phiona moloi MametjaPhiona moloi Mametja
Phiona moloi Mametja
While breast milk is the recommended food for infants up to at least six months, exogenously derived compounds such as trace elements have been widely reported in human milk which may make it become toxic or a source of pollutants to the infants. Numerous short- and long-term health effects have been associated with high body—burdens of trace elements, which are amplified in infants. The current study determined the levels and possible contributing factors of six trace elements in breast milk of nursing mothers from a local hospital in Pretoria. Extraction of trace elements employed a digestion technique using perchloric and nitric acid in a ratio of 1:3, while Inductively Coupled Plasma–Membrane Spectrophotometry was used to identify and quantify their levels in breast milk. Concentrations of Cr and Mn were the highest in breast milk, with values ranging from 0.30 to 5.72 µg/L and 0.23 to 5.13 µg/L, respectively. Levels of Co, As, Pb and Cd ranged from <LOD to 0.2 µg/L, <LOD to 2.29 µg/L, 0.05 to 1.06 µg/L, and 0.004 to 0.005 µg/L, respectively. Levels of Cr, Mn and As were higher than the recommended limits from WHO (World Health Organization) in some milk samples. Dietary assessments showed minimal risk for the infants through breastfeeding at this stage; however, prolonged exposure to other sources of these toxic trace elements may pose a serious health risk for the infants. The nature of employment, infant birth weight, passive smoking and maternal diet were the significant factors noted to contribute to trace metal levels in breast milk.

9 August 2018 in Journal of Environmental and Public Health
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Journal Article
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SNSenzeni Nyathi
Senzeni Nyathi
JOJoshua O Olowoyo
Joshua O Olowoyo
AOAgboola Oludare
Agboola Oludare
Objective. Scavenging is a source of income for most unskilled people in the developing countries. The present study investigated the perception of scavengers on scavenging and related health hazards from the Onderstepoort waste dumpsite in Pretoria, South Africa. Methods. Primary data were obtained through observation and implementation of a questionnaire to a total number of 53 scavengers (27 females and 26 males). The questionnaire was structured to extract information that included perceptions of scavengers about their activities, health implications of scavenging, monthly income, and behavioural norms. Results. Educated scavengers had high school education. The period of scavenging ranged from 10 to 15 years. The majority of scavengers did not use protective clothing. However, few used gloves and boots picked from the dumpsite. Common health issues reported included back pain, headache, diarrhoea, and shortness of breath. Some sustained injuries from sharp objects. Scavengers stored food among the waste; food could be either brought from home or bought from the vendors who cook at the dumpsite. Some drank bottled water picked from the waste. Eighty-five percent of females cleaned themselves immediately after work in temporary shacks at the dumpsite, while all males bathed at home. The average monthly income from scavenging was approximately R1372 (approximately $91 (US)). Women scavengers liked their job despite associated health risks. Conclusion. Scavengers would benefit if government and nongovernmental organisations educate them on the significance of protective clothing and good hygiene. Policymakers should assist the scavengers by providing necessary workshops on-site that will assist them to change their behaviour.