Heavy metals and potential health risk assessment of Lactuca sativa and Daucus carrota from soil treated with organic manures and chemical fertilizer.

The large-scale production of food crops with heavy application of chemical fertilizers in the effort to meet the astronomical increase in food demands may be counterproductive to the goal of food security. This study investigated the effect of different soil treatments on the levels of heavy metals (Cr, Cu, Fe, Ni, Pb, and Zn) in two types of vegetables Lactuca sativa (lettuce) and Daucus carrota (carrot). The potential carcinogenic and non-carcinogenic health risks from their consumption were also evaluated. Planting experiment was set up in a randomized block design, with different soil treatments of soil + cow dung (CD), soil + sewage sludge (SS), soil + chemical fertilizer (nitrogen-phosphorus-potassium (NPK)), and untreated soil (UNTRD). The vegetables were harvested at maturity, washed with distilled water, and subjected to an acid digestion process before the levels of heavy metals were measured by inductively coupled plasma spectrometry (ICP-MS). The mean concentrations of the metals in the vegetables across all treatments were below the maximum permissible limits. The pattern of heavy metal accumulation by the vegetables suggested that the lettuce from SS treatment accumulated higher concentrations of heavy metals like Cr (0.20 mg/kg), Cu (3.91 mg/kg), Ni (0.33 mg/kg), and Zn (20.44 mg/kg) than carrot, with highest concentrations of Fe (90.89 mg/kg) and Pb (0.16 mg/kg) recorded in lettuce from NPK treatment. The bioaccumulation factor (BAF) showed that lettuce, a leafy vegetable, has bioaccumulated more heavy metals than carrot, a root vegetable. The BAF was generally below the threshold value of 1 in both vegetables, except in lettuce from NPK and CD treatments and carrot from NPK treatments, with BAF values of 1.6, 1.69, and 1.39, respectively. The cancer risk assessment factors were well below the unacceptable maximum range of 10-4 suggesting that consuming these vegetables might not expose an individual to potential risk of cancer development. The hazard quotient estimations were below the threshold values of 1 for all heavy metals; however, the hazard index (HI) values of 1.27 and 1.58 for lettuce from NPK and SS treatments indicate a potential non-carcinogenic health risk to consumers from intake of all the heavy metals.

Trace metals concentrations in fresh milk from dairy farms and stores: An assessment of human health risk.

Milk may be consumed daily for the supply of essential nutrients in the body, however, depending on the source, milk may contain different concentrations of trace metals. The present study investigated the presence of trace metals in fresh milk purchased from different dairy farms and stores to determine the possible health risks to humans. A total of 15 fresh milk samples were purchased from various dairy farms (7 fresh milk samples) and stores (8 milk samples). Trace metals in collected milk samples were determined using Inductively Coupled Plasma Mass Spectrometer (ICP-MS). The human health risk was determined through the Hazard Quotient (HQ), Carcinogenic and Non-carcinogenic Risk. The results showed the presence of trace metals in fresh milk stores in the following order Pb>As>Se>Cr>Ni. The highest concentration for all the elements was recorded in Mg from milk purchased from the stores and ranged from 3.37±0.16 mg/L to 4.70±0.43 mg/L. In all the milk samples analyzed, levels of As, Pb, Se, Cr, and other elements were within the acceptable range recommended by the World Health Organization (WHO). Differences obtained in the concentrations of trace metals from both the purchased milk samples and those from the dairy farms were not significant (p<0.05). The Estimated Daily Intake (EDI) and Hazard Quotient Index showed no potential health risk for each trace metal indicating no health risk for the milk consumers at this stage. The traces of trace metals in the milk samples suggest the need for regular monitoring of trace metals in milk samples because prolonged exposure to these trace metals may seriously endanger the health of consumers.

Blood lead concentrations in exposed forecourt attendants and taxi drivers in parts of South Africa.

BACKGROUND: Leaded fuel was banned in South Africa in 2006, in order to improve human health and reduce environmental pollution. Lead (Pb) has been suggested to contribute to the development of neurodegenerative disorders, and the role of respiratory exposure to Pb from petrol fumes should not be neglected in this context. In addition to Pb, petrol contains various harmful chemicals including other neurotoxic metals and hydrocarbons. OBJECTIVES AND METHODS: Here, we investigated concentrations of Pb and other metals in blood from petrol station forecourt attendants (n = 38), taxi drivers (n = 21), and unexposed controls (n = 36). Taxi drivers and forecourt attendants were divided into three groups each, based on number of years worked. A questionnaire was designed to investigate the health status of the participants. Blood samples were collected by medical professionals and analyzed for metal concentrations by ICP-MS. RESULTS: A positive correlation between number of years worked and Pb blood concentrations was found. The highest Pb concentration (60.2 µg/L) was observed in a forecourt attendant who had worked 11-20 years, and the average Pb concentration in this group (24.5 µg/L) was significantly (p < 0.05) higher than in forecourt attendants who had worked 2-5 years (10.4 µg/L). Some individuals had elevated concentrations of manganese, arsenic, cadmium, chromium and cobalt, yet not significantly elevated at the group level. The blood levels of arsenic appeared to be related to smoking. Mood swings, dizziness, headaches and tiredness were reported by the workers. CONCLUSION: Blood Pb concentrations in petrol station forecourt attendants and taxi drivers exposed to leaded petrol are elevated and correlate to exposure time. A health monitoring program should be erected for all individuals working in these industries, and preventive measures should be implemented to eliminate metal exposure from petrol.

Determination of pesticide residues in rooibos (Aspalathus linearis) teas in South Africa.

An efficient gas chromatography-mass spectrometry approach was used in this study to quantify 13 pesticide residues in rooibos teas purchased from registered retail outlets in South Africa between November 2019 and April 2020. A QuEChERS (Quick, easy, cheap, effective, rugged, and safe) procedure was used to extract pesticides using 7.5 mg of graphitized carbon black (GCB), 50 mg of primary secondary amine (PSA), and 150 mg of anhydrous MgSO4. In order to compensate for the matrix effect, matrix matched calibration curves ranging from 10 µg/kg-500 µg/kg were applied for accurate quantification. For validation purposes, accuracy tests were conducted using a blank tea sample spiked with pesticide standards at two different concentrations (10 and 100 µg/kg). Most of the analytes were recovered within acceptable recovery ranges (72-106%), with a relative standard deviation of less than 20%. The limits of quantification were low, all falling below 10 µg/kg which meets the maximum residue limits (MRLs). The validated method was used to analyze 100 tea samples, and among the pesticides analyzed, deltamethrin and lambda-cyhalothrin were detected in only one samples at a concentration (92.11 and 66.41 µg/kg, respectively) below the MRLs stipulated by the European Union. The level of pesticides that are commonly used in tea should be checked often.

Occurrence of antibiotics in wastewater from hospital and convectional wastewater treatment plants and their impact on the effluent receiving rivers: current knowledge between 2010 and 2019.

The increased usage of antibiotics over the recent years has been of great concern all over the world. It is estimated that about 100,000 tons to 200,000 tons of antibiotics are being consumed worldwide. This increased consumption of antibiotics is worrisome as this has resulted in their detection in wastewater treatment plants' (WWTPs) effluent due to the inability of WWTP to remove them during treatment processes. The antibiotics may emanate from hospital effluents, surface waters, and sediments around the world. However, the migration of antibiotics to the environment is detrimental to public health since it can lead to antibiotics resistance in both humans and animals which has now been reported to be one of the biggest threats to public health in this twenty-first century. This present review work established from literature the presence, concentrations, and types of antibiotics both in influents and effluents of various waste treatment plants, natural water bodies, and hospital wastewaters from different countries over the past 10 years (2010-2019). A total of 78 published articles containing information on the presence of antibiotics in convectional and hospital wastewater and also in surface water were retrieved from scientific databases such as ScienceDirect, Google Scholar, PubMed, and Web of Science. A total of 39 different types of antibiotics from 10 different classes of antibiotics and others were recorded. Among the articles reviewed, the most frequently detected antibiotics are the classes of sulfonamides (sulfamethoxazole) which were present in almost all the WWTPs at concentrations as high as 10-800 ng/l in influent and 3600-68,700 ng/l in effluent samples. Macrolides (clarithromycin, erythromycin, azithromycin), trimethoprim, quinolones (ofloxacin, ciprofloxacin, norfloxacin), and tetracyclines (tetracycline) were also highly present in all treatment plants. ß-Lactam antibiotics were seldom detected which might be due to hydrolysis. Most of the antibiotics present were recorded in Asian countries such as China and Singapore which have occurrence frequency of 6-30% and in European countries such as Greece and Spain with frequencies of about 6-10%. Future researches on the need for development of more reliable and cost-effective technologies for antibiotic removal such as advanced oxidation processes and remediation methods are suggested for more research attention.

Prevalence of geophagia and its contributing factors among pregnant women at Dr. George Mukhari Academic Hospital, Pretoria.

INTRODUCTION: Geophagia is very common among pregnant women, particularly in Africa. There are many reasons given for geophagia such as cultural, medicinal and religious, making it an acceptable norm regardless of health risks involved. OBJECTIVES: The study explored prevalence and factors influencing geophagia among women visiting an antenatal clinic in Pretoria. METHODS: A quantitative survey was done on a convenience sample of 597 pregnant women and structured interviews conducted. Statistical analysis was done using simple percentage and interview data analyzed using Epi Info statistical software. RESULTS: Geophagia was reported by 54.0% of the women (n=323) and of these, 75.2% (n=243) ate at least 3 teaspoons per day. Reasons for the practice ranged from simple unexplained craving to belief that soil acts as an iron supplement. The study revealed that education levels did not act as a contributing factor as both literate and illiterate women were consumers. Partners of consumers played a key role in influencing the practice as most consumers were not married. CONCLUSION: Geophagia is practiced by a considerable proportion of pregnant women in this area. Greater vigilance may be needed as part of the antenatal classes to avoid potentially harmful effects of the habit.

An assessment of university students and staff perceptions regarding the use of human urine as a valuable soil nutrient in South Africa.

BACKGROUND: The declines in soil fertility associated with insufficient commercial fertilizers have resulted in the use of organic manure (human urine and faeces) as a source of fertilizers for production and cultivation of crop plants. The aim of this study was to assess perceptions of students and workers at the University of Limpopo (Medunsa Campus) regarding the fertilizing effect of urine. METHODS: A total of 225 questionnaires were administered to staff and students. The questionnaire sought to establish the knowledge, attitude and behavioural changes as regards the use of urine as a fertilizer for the cultivation of vegetables. RESULTS: Descriptive statistical analysis of the data indicated that 86.8% of the respondents were unaware of any human urine use as a fertilizer, 82.7% and 81.1% would not eat spinach and maize fertilized with urine respectively. Only 38.3% said they would eat vegetables fertilized with animal urine making it more tolerable as compared to human urine. Health reasons were given as the main reasons why respondents were unwilling to eat crops fertilized with human urine. However, 69.9% of the respondents [74.3% females, 69.9% students, 75.0% (27-36) age group] were willing to change their attitudes and unwillingness if they were better informed about the safety of human urine use for agricultural purposes. CONCLUSION: Education, awareness and reassurance on the importance and safety of urine would have to be done so that urine for agricultural purposes could become more acceptable to people.

Comparing the levels of trace metal from two fish species harvested from treated waste water in Pretoria, South Africa.

The persistent problem of water scarcity with the ever increasing demand of water has necessitated the reuse of effluent in agriculture. The present study evaluated the reuse of treated waste water and bioaccumulation properties of two fish species from a manmade lake. Trace metals content of two fish species: Clarias gariepinus and Cyprinus carpio and levels of trace metals from waste water in the lake where the fish species were harvested were determined by Inductive Couple Plasma-Optical Emission Spectrometer (ICP-OES). The trace metal values from fish samples ranged between 0.45-4.41 microg g(-1) for Cu, 16.45-72.23 microg g(-1) for Zn, 1.92-4.71 microg g(-1) for Cr, 2.45-5.65 microg g(-1) for Ni, 10.23-44.31 microg g(-1) for Mn, 9.67-46.59 microg g(-1) for Fe and 0.12-0.56 microg g(-1) for Pb. The carp exhibited a significantly higher concentration for the trace metals for all the parts analyzed (p<0.01). The levels of trace metals concentration from Cyprinus carpio was in the order liver>gill>muscle>bone and metal accumulation was in the order Zn>Fe>Mn>Cr>Ni >Cu>Pb. The concentration of trace metals such as zinc, iron, chromium and nickel were higher than the recommended legal limits for human consumption. The result revealed that properly treated waste water could be used for the purpose of aquaculture. Clarias gariepinus bio accumulated more trace metals from the lake when compared with Cyprinus carpio.

Investigating Jacaranda mimosifolia tree as biomonitor of atmospheric trace metals.

Studies on the use of tree bark as biomonitors for environmental pollutants are still very scarce. We evaluated the reliability of using Jacaranda mimosifolia, a common tree in Tshwane City of South Africa, as a suitable biomonitor of atmospheric trace metals. Bark samples were collected from ten different locations during two sampling periods. The concentrations of the metals were determined by inductively coupled plasma mass spectrometry. The concentrations of the metals were 33.2-1,795 microg/g (Pb), 21.4-210 microg/g (Cu), 68.4-490 microg/g (Zn), 30.6-2,916 microg/g (Cr), 0.12-1.34 microg/g (Cd), and 6.04-68.0 microg/g (V), respectively. The differences obtained for the results from different sites were significant (p < 0.05). A significant difference was also observed between the two sampling periods. The trace metals concentrations suggested that automobile emissions are a major source of these metals. The study also confirms the suitability of J. mimosifolia as a biomonitor of atmospheric deposition of these metals.