Concentrations of pesticide residues in grasses and sedges due to point source contamination and the indications for public health risks, Vikuge, Tanzania

doi:10.1016/j.chemosphere.2005.03.059

Chemosphere

Volume 61, Issue 9, December 2005, Pages 1293-1298

https://doi.org/10.1016/j.chemosphere.2005.03.059 Get rights and content

Abstract

The concentrations of organochlorine pesticide residues were determined in roots and leaves of giant sedges (Cyperus exaltatus), fresh leaves and dry hay of guinea grasses (Panicum maximum), and in stems and leaves of elephant grasses (Pennisetum purpureum) in the vicinity of a point source of contamination, an old storage site at Vikuge farm in Tanzania. The GPC-cleaned extracts were analyzed by GC-ECD and GC/MS. The concentrations of total DDT ranged from 83 to 18274 ng/g, 166 to 7922 ng/g, and 68 to 405 ng/g, on fresh weight basis, in C. exaltatus, P. maximum and P. purpureum, respectively. The concentrations of total HCH were up to 74 ng/g fw in leaves of C. exaltatus, 43 ng/g dw in dry hay of P. maximum, and 10 ng/g fw in stems of P. purpureum. Aldrin and dieldrin were only detected in C. exaltatus and their concentrations were up to 11 and 8 ng/g fw, respectively. The strong positive correlations between the concentrations of the detected compounds suggest a common source. The concentrations of total DDT were far above the Australian extraneous maximum residue limit in primary animal feedstuffs. These findings indicate potential risks and concerns for livestock and public health. The concentrations of aldrin, dieldrin and lindane were lower than the Australian limits.

Introduction

Pesticides have played significant roles in agriculture and public health programmes (WHO, 1990). However, the increase in pesticide use has caused great concern over the presence of pesticides in the environment and the threat they may pose to wildlife and humans (Plimmer, 2001). Their use and abuse can lead to serious food quality problems, fish kills, reproductive failure of birds, illnesses in people, and reduction of beneficial species, such as pollinating insects. Usually this is the result of misapplication, improper storage, or disposal of pesticides (Norstrom and Muir, 1994). Living organisms play a significant role in pesticide distribution. This is particularly important for pesticides which can bioaccumulate in living creatures, since their concentrations increase over time, and if the organisms are consumed by higher organisms which also can store these pesticides, concentrations can reach higher values in the higher organisms than are present in the environment (Wania and Mackay, 1996). In this regard, it should be remembered that humans are at the top of the food chain and so may be exposed to these high concentrations when they eat food animals which have bioaccumulated pesticides (Miglioranza et al., 1999).

Plants can absorb pesticides from soil or absorb the volatile compounds in air due to atmospheric deposition (Paterson et al., 1994). The residues in plants such as grasses may be ingested by herbivores such as cattle, and eventually find their way into meat and milk (WHO, 1990).

This work was conducted to investigate the concentrations of organochlorine pesticide residues in grasses and sedges due to point source contamination, and to evaluate their indications for public health risks. Although the persistent organochlorines have been banned in most countries, Tanzania like any other developing countries has large stocks of obsolete pesticides which are potential causes of point source contamination due to illegal uses or improper storage.

Section snippets

Sampling

The old storage site at Vikuge farm (6°47′S, 38°52′E) in the Coast region, Tanzania (Fig. 1), was taken to be the point source for purposes of this study. At Vikuge farm, pastures which include Panicum maximum (Guinea grass), Pennisetum purpureum (elephant grass), and Cyperus exaltatus (giant sedges), are grown, harvested, dried and bound. The farm has also been used as a storage site for tons of obsolete pesticides. The old store collapsed in 1990, leaving the pesticides exposed to rain, wind

Results and discussion

The compounds detected were p,p′-DDT, o,p′-DDT, p,p′-DDE, p,p′-DDD, o,p′-DDE, o,p′-DDD, α-HCH, β-HCH, γ-HCH, δ-HCH, ε-HCH, aldrin and dieldrin. Their concentrations are presented in Table 1, Table 2.

Conclusions

The concentrations of pesticides and metabolites in grasses and sedges in the vicinity of the point source, an old storage site at Vikuge farm in Tanzania were found to be very high. These findings indicate potential risks and concerns for livestock and public health. The present findings point out to the urgent need for remedial actions to solve the problem through decontamination at the point source from which the pesticide residues continue to be released into animal feeds. It is also

Acknowledgements

The German Academic Exchange Service (DAAD) is highly acknowledged for funding this work. Prof. Dr. A. Kettrup, Dr. D. Martens, Mr. S. Forster, and the Institute of Ecological Chemistry of the GSF-National Research Centre for Environment and Health (Germany) are kindly acknowledged for facilitation of the GC/MS analyses.

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