An overview of biodiesel soil pollution: Data based on cytotoxicity and genotoxicity assessments

Abstract

Biodiesel production has received considerable attention in the recent past as a nonpolluting fuel. However, this assertion has been based on its biodegradability and reduction in exhaust emissions. Assessments of water and soil biodiesel pollution are still limited. Spill simulation with biodiesel and their diesel blends in soils were carried out, aiming at analyzing their cytotoxic and genotoxic potentials. While the cytotoxicity observed may be related to diesel contaminants, the genotoxic and mutagenic effects can be ascribed to biodiesel pollutants. Thus, taking into account that our data stressed harmful effects on organisms exposed to biodiesel-polluted soils, the designation of this biofuel as an environmental-friendly fuel should be carefully reviewed to assure environmental quality.

Introduction

The use of plant oils as a fuel in the compression ignition engine is as old as the engine itself [1], [2]. Biodiesel, a mixture of mono-alkyl ester obtained from renewable sources of biologic origin, has gained importance in the recent past for its ability to replace fossil fuels [3]. The increasing production and consumption of biodiesel has encouraged environmental researchers to assess its hazard and fate in the environment.

The anthropogenic pollution of soil has become an issue of intensive scientific research since the end of the 20th century [4]. Genotoxic compounds in soil may affect living organisms’ health, including human beings, by exposing them through different pathways, such as ingestion of plants that uptake soil pollutants and leaching of compounds from soil to ground and surface water used as drinking water [5]. Oil spillages have currently become as frequent as increasing industrialization rate and consumption of energy worldwide [6]. Thus, like other fuels, biodiesel can reach the environment through accidental releases and/or routine losses associated with the use of this biofuel.

Hazard identification of environmental pollutants is measured by employing different biological assays. Assessing the toxic contamination of a solid medium like soil is not a simple task, due to the sterile conditions required by most of the bioassays commonly applied to genotoxic screenings. Assays conducted with plants and bacteria, such as Salmonella mutagenicity test and genotoxicity Allium cepa test, are among the most widely used test systems to evaluate soil quality. However, other assays, like in vitro tests with cultured mammalian cells, have been successfully used to assess cytotoxic and genotoxic potentials of environmental samples, including soil samples [7].

The analysis of different endpoints is a requirement for an accurate environmental investigation. Salmonella/microsome assay is a widely accepted short-term test used to detect agents that can produce genetic damage that leads to gene mutation [8]. The A. cepa test is a plant test system capable of evaluating chromosomal aberration (CA) and micronucleus (MN) induction [9]. Since the MN results from acentric fragments or whole chromosomes that were not incorporated into the main nucleus during the cell division cycle [10], the MN test is a valid alternative to predict outcomes from the CA test, making the evaluation simpler and faster [11]. To improve the throughput capacity of the MN test more and more, a flow cytometry-based in vitro MN assay has recently been developed, allowing MN measurements in a large number of cells in a short period of time [11], [12], [13]. Cytotoxic evaluations are also important due to their association with environment-related disease [14] and the fact that cytotoxic effects can mask genotoxic potentials of test agents.

Aiming at predicting the harmful effects of soil contamination with biodiesel and their diesel blends on living organisms’ health, the purpose of the present study was to assess the cytotoxic and genotoxic potentials of soil polluted with these fuels using different biological assays, such as detection of changes in mitochondrial membrane potential (ΔΨ_m); apoptosis recognition by Annexin V; in vitro MicroFlow^® kit (Litron) assay; Salmonella mutagenicity assay and A. cepa test.