Ecotoxicology is the study of the effects of natural and synthetic chemicals (stressors) in the biosphere.
Ecotoxicology has been described as a multidisciplinary field incorporating concepts arising from toxicology, biology, analytical, environmental and organic chemistry, physiology, ecology, genetics, microbiology, biochemistry, immunology, molecular biology, soil, water and air sciences, and economics. The increasing accumulation of both natural and industrial chemical contaminants in freshwater is one of the key environmental problems facing humanity.
In biosolids, microcontaminants originate from various industrial and domestic sources and include metals, pharmaceuticals and personal care products (PPCP) and industrial chemicals.
There is limited information on the potential adverse effects of these chemicals therefore it is challenging to establish relevant risk assessment.
The research of the Ecotoxicology group is focused on the characterisation of the harm caused by the contaminants. In particular, Ecotoxicologists at the CIBR are working to answer what micro-contaminants are commonly found in biowastes in New Zealand and where do they come from; as well as what effects do they have in the environment individually, and as complex mixtures? The techniques they use include analytical chemistry and bioassays based on different levels of biological organisation.
The research is continuing to better characterise the risk of these micro-contaminants and to reduce their presence in biosolids.
Bioassay tests at CIBR – a selection
Our research uses a battery of tests (called bioassays) ranging from in vitro tests to whole organism tests to evaluate the biological response (as outlined below) associated with individual chemicals or chemical extracts of biosolids. This will help determine the most significant components in the complex mixtures that are causing effects.
We have undertaken research on: the plastisizer Bisphenol A, the widely used anti-microbial agent triclosan and carbamazepine, a psychiatric drug and technical nonylphenol, galaxolide (poloycyclic msuk) and diethylhexylphthalate – the latter three compounds being typically present in biosolids at high concentration – in addition to extracts of biosolids from a range a treatment plants across the country.
Survival and reproduction
The toxicity of those chemicals are assessed using an internationally recognised standard earthworm test where survival and the production of neonates are monitored to provide an indication of toxicity. Now the chemicals are being tested in the same assay in binary combinations. The results should provide information about whether the effects of mixtures of chemicals modulate their toxic effects.
Immune cells response
The immune cells of earthworms provide a similar function in the earthworm to the white blood cells in humans. They are therefore an excellent target to research the response of earthworms to range of pollutants. In order to investigate these immune cell responses, CIBR researchers are using a flow cytometry that can separate and count earthworm immune cells and provide an indication of how stressed the animals are. We can also assess whether the chemicals are making them more susceptible to diseases.
Currently we are investigating the application of molecular techniques to assess the response of earthworms to contaminants.
In vitro assays are typically undertaken in small plates, and typically examine a specific pathway of toxicity. We use a range of cell-based and a cellular in vitro assays to evaluate different mechanisms of effect that may be elicited by individual chemicals or chemical extracts of biosolids. A particular focus is the endocrine system, which is responsible for hormone production, and endocrine disruption is one of the major causes for environmental concern. Specifically, we are looking at the effects on estrogen and androgen receptors (cell-based assays) and thyroid receptors (acellular assay). In addition, we are looking at general measures of toxicity to cells (cytotoxicity), and oxidative stress, and the induction of detoxicification enzymes. We have previously investigated the mutagenicity of biosolids extracts, although limited activity has been observed and we no longer routinely use this assay.
This bioassay investigates how well soil microbial communities have become adapted after exposure to pollution. This is tested by comparing soil microbial communities that were exposed to those communities that were not exposed to pollution. By subjecting these microbes to increasing levels of a pollutant of interest (for example triclosan), we can determine whether soil microbial community have adapted and thus have become more tolerant to pollutants such as triclosan.