Levels of formaldehyde and acetaldehyde in selected bottled drinking water sold in urban areas in Tanzania

The levels of formaldehyde and acetaldehyde in bottled drinking water and the effect of storage time and storage conditions on their levels were determined. A total of 144 samples of six brands of bottled drinking water were purchased from Dar es Salaam, Iringa, Mwanza and Arusha regions in Tanzania. Analysis was performed using HPLC on the 1st day and after 14 and 42 days of storage in a refrigerator, at room temperature and exposure to sunlight. The levels of formaldehyde and acetaldehyde in the refrigerated samples ranged from 2.46 to 19.25 μg/L and from not detected (ND) to 58.70 μg/L, respectively. In samples stored at room temperature, the levels of formaldehyde and acetaldehyde were up to 23.26 μg/L and 36.10 μg/L, respectively.  The highest levels of formaldehyde and acetaldehyde in samples exposed to sunlight were 46.0 μg/L and 187.0 μg/L, respectively. The lowest levels of the aldehydes were found in refrigerated samples and the highest levels were in samples exposed to sunlight. The levels of these aldehydes increased with increased storage time. The levels were below the WHO acceptable limits; however, the findings indicate that the levels could be elevated with increased storage time and exposure to sunlight.Keywords: Bottled drinking water, formaldehyde, acetaldehyde, storage time, storage condition

Determination of Dichlorodiphenyltrichloroethane (DDT) and metabolites residues in fish species from Eastern Lake Tanganyika

In this study, the levels and status of dichlorodiphenyltrichloroethane (DDT) residues in fish samples collected from Eastern Lake Tanganyika were investigated. The analytes were determined using gas chromatography equipped with an electron capture detector (GC–ECD) and by gas chromatography-mass spectrometry (GC-MS). The compounds p,p’-DDE (4,4’-DDE), p,p’-DDD (4,4’-DDD), o,p’-DDT (2,4’-DDT) and p,p’-DDT (4,4’-DDT) were detected in all the samples, with total DDT concentrations ranging from 23 ± 8.3 to 339 ± 27 μg kg–1 fresh weight and 1736 ± 1388 μg kg–1 to 25 552 ± 4241 μg kg–1 lipid weight. The highest concentrations of total DDT were detected in Lates stappersii species. The ratios of the metabolites (DDD + DDE) to the parent compound (p,p’-DDT) were low (< 1) in all the fish samples, indicating exposure to fresh DDT. The concentrations of the DDT residues exceeded the extraneous maximum residue limit of 1.0 μg kg–1, indicating risks and concerns for public health and the environment because of the indication of fresh application of banned pesticides and bioaccumulation. There is need for continued monitoring of the residues in Lake Tanganyika environs and controlling the pesticides used in the area.Keywords: Pesticides, DDT, fish, lake, Tanzani

Assessment of pesticide residues in tomatoes and watermelons (fruits) from markets in Dar es Salaam, Tanzania

This study investigated the levels of pesticide residues in selected fruits from major markets in Dar es Salaam city. Samples of tomatoes and watermelons were analysed for eighteen organochlorine, organophosphorus and pyrethroid pesticide residues. Extraction was performed using acetone followed by dichloromethane: cyclohexane mixture and the extracts were cleanedup using florisil. The compounds were determined by gas chromatography–mass spectrometry (GC–MS). Pesticides and metabolites were detected in 95.8% of the samples. The compounds detected included chlorpyrifos, α-endosulfan, β-endosulfan and cypermethrin and their highest concentrations were 3810 ± 50, 370 ± 20, 120 ± 6 and 50 ± 4 ng/g, respectively. Others were p,p'- DDD, o,p'-DDD, p,p'-DDE and α-HCH with highest concentrations varying from 1 ± 0.5 to 20 ± 1.2 ng/g. There were no significant variations in concentrations of the pesticide residues between the fruits and among the sampling sites, indicating similarities in contamination patterns. The concentrations of the contaminants were above the maximum residue limits (MRLs) in 41.7% to 50% of the tomatoes and watermelons indicating risks and concerns for public health. The Tanzanian agrochemicals and food regulatory agencies (e.g. TPRI, TFDA and TBS) and the government in general should ensure strict applications of laws that regulate pesticides in the country and develop effective educational programmes for farmers to apply good agricultural practices such as reducing the use of pesticides, applying appropriate pesticides and doses, and restrict the spray before harvesting. The consumers should thoroughly wash or process the fruits to reduce the levels.Keywords: Pesticides, Fruits, Food, Contamination, Tanzani

Variations of Concentrations of Lead, Zinc, Iron, Copper and Cadmium in Urine of Primary School Pupils in Relation to Age, Sex and Academic Performance

This study was conducted in order to assess the variations and correlations in the concentrations of lead, zinc, iron, copper and cadmium metals in the urine samples of selected primary school pupils with respect to their sex, age and academic performance. Urine samples were collected from 240 pupils in Dar es Salaam, Tanzania and then digested in concentrated acids and analysed using atomic absorption spectrometry (AAS). Lead, zinc, iron and copper were detected in most of the urine samples. Cadmium was not detected in any of the samples. The mean concentrations of lead, zinc, iron and copper in the samples from different classes ranged between 0.27–0.90, 0.59–0.78, 1.56–2.32 and 0.005–0.01 mg/L, respectively in pupils with high academic performance, and 0.37–0.71, 0.56–0.81, 1.79–2.55 and 0.005–0.01 mg/L, respectively in pupils with low performance. The overall mean concentrations of the metals ranged between 0.01–2.04 and 0.01–2.17 mg/L in males and females, respectively. There were no significant differences in most of the concentrations of the heavy metals in pupils’ urine samples between the two sexes. The findings indicated some significant positive correlations between the pupils’ age and the concentrations of lead and iron in urine samples, while there were no significant correlations for zinc and copper. Some of the concentrations of the heavy metals showed significant negative or positive correlations with the academic performance of the pupils. Therefore, the concentrations of the heavy metals were correlated with age, sex and academic performance in some samples. The concentrations of lead were generally alarming. Keywords: Heavy metals; children urine; age; sex; academic performance; Tanzani

Polycyclic aromatic hydrocarbons (PAHs) contamination in coastal mangrove ecosystems of the Zanzibar archipelago

The objective of this study was to determine the levels of polycyclic aromatic hydrocarbons (PAHs) in sediments and crabs in the mangrove ecosystems of Zanzibar. Sediments and crabs from eight sampling sites were analysed for eleven selected PAHs. Samples were extracted with dichloromethane by ultrasonication, cleaned-up using column chromatography, and concentrated using a rotary evaporator. GC-MS was used in the analysis of the samples. In general, all eleven PAHs were detected in crab and sediment samples. Total concentrations of PAHs ranged from 1.70 to 28.66 ng/g fresh weight (fw) in crabs, and from 20.14 to 81.94 ng/g dry weight (dw) in the sediments. The levels of the PAHs are thought to be related mostly to petrogenic and pyrogenic sources from anthropogenic activities. The results from this study demonstrated the existence of PAHs contamination in mangrove ecosystems of Zanzibar, and it is recommended that a PAHs contamination monitoring programme be established.