Bioassay: Quality of Water

Categories: Biology

Essay, Pages 5 (1170 words)

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Introduction

A bioassay is an analytical method that is used to determine the potency or concentration of a substance by its effect on tissues or living cells. It is also a quantitative biological assay that is used to estimate the relative potency of a compound by observing either in vivo which is through the effect on living cells or in vitro which is through tissue or cell culture system. It can be either direct or indirect and quantitative or qualitative. Biological hazards can be detected by using bioassay method.

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It also gives quality assessment of a mixture. Bioassay is often used in monitoring water quality and sewage discharge and its impact on surrounding. It is also used to assess the environmental impact and safety of new technologies and facilities.

Current Status

To access the quality of water, various in vitro bioassays are introduced. Many studies and publications are done for in vitro bioassays. These studies have shown the suitability of in vitro bioassays to assess water quality and demonstrated the added benefit of more comprehensive water quality evaluation.

Purpose

As a surrogate measure for a wide range of chemical compounds
To assess and monitor water and wastewater treatment efficacy
To detect toxic transformation products produced by water treatment
To benchmark different water sources and allowing determination of the most suitable source for a specific use

Benefits

Ability to quantify some level of mixture effects
Ability to integrate concentration and potency
Ability to detect chemical contaminants by their effect
Ability to complement current analytical methods
Ability to complement current analytical methods and identify biologically active contaminants in effects-directed analysis (EDA)

Drawbacks

limitations in the application of in vitro bioassays for comprehensive evaluation of bioactivity
Solid-phase extraction (SPE) are mainly used
SPE protocol is not likely to extract most metals and other inorganic salts
Highly volatile species are not easily trapped and concentrated such as trihalomethanes and other volatile organic compounds
Quality Assurance (QA) and Quality Control (QC)
For in vitro bioassays screening, it is strongly recommended that at least one positive control substance be spiked into the matrices of interest for each bioassay endpoint evaluated
Method detection and reporting limits for bioassay should be based on the detection limit of the assay itself and the entire method from sample collection to data processing.

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Limited information is available on holding times, container types, preservative effects and other aspects of QA/QC which is relatively more defined for targeted analytical methods
Data on these types of QA/QC as applied to in vitro bioassays are relatively sparse and should be addressed before wider application of in vitro bioassays in regulatory contexts
In vitro bioassays alone are not capable of assessing the safety of water
In vitro bioassays should be used to access not only the quality but also safety of the drinking water
The BRAVE initiative is supported by various water research providers to develop a research map towards the goal
The think-tank has identified four main areas to focus the efforts on which are identifying adverse effect endpoints relevant to water consumption, translating in vitro responses to in vivo effects, converting in vitro concentration to in vivo exposure dose and adapting mixture modelling to support each of these steps
The use of bioassays will increase the cost of water testing
Compared to most instrumental analyses for trace organic compounds, bioassays require far less costly hardware and methodologies needed are generally familiar to utilities/agencies that conduct microbiological testing
Bioanalytical tools will detect activity that cannot be related to a specific chemical, thereby making it difficult to interpret bioassay results
Different types of bioassays will react to different chemicals
Bioassays that are used to measure specific effects (such as receptor-mediated effects) are often responding to a limited scope of compounds
Testing with in vitro bioassays may introduce uncertainty about the safety of drinking water that has already been proven compliant with current regulation
Results from in vitro bioassays are too variable and vary between laboratories

Future Application

Firstly, in order to overcome limitation caused by SPE, specialized methods are required to trap chemicals based on physical-chemical properties and not one extraction/concentration procedure will isolate all chemicals within a complex aqueous mixture. In consequence, multi-layer SPE cartridges with several different sorbents to capture chemicals with a wide range of physiochemical properties have recently been applied to extract water samples for bioanalysis.

Secondly, in vitro bioassays can expand analytical universe a little further into the unknown, thereby providing a more comprehensive evaluation of water quality and more rapidly identifying substances which may pose a risk to public health.

Thirdly, issues with loss of chemicals by sample preparation can be overcame. While SPE pre-concentration is commonly used when applying in vitro bioassays to environmental water samples, the availability of powdered cell culture media means that it is possible to dose un-extracted water samples for testing at a relative enrichment factor (REF) close to 1 (an REF of 1 means an undiluted sample, with an REF > 1 indicating a concentrated sample and an REF < 1 a diluted sample). In a recent study, Niss et al. (2018) applied this approach and were able to detect a range of responses in the water samples, including estrogenicity and aryl hydrocarbon activity.

Fourth is introduction of in vitro bioassays that are able to detect a wider range of contaminants. While the response of these assays cannot be simply translated into a chemical equivalent, there are several proposals to develop meaningful and implementable trigger values and practical operational responses to bioassay results.

Fifth, an important aspect in the application of bioassays in water quality assessment is the development of response mechanisms for positive results. One proposed method is the development of benchmark values which have been termed Effects Based Trigger values (EBT). Various approaches have been proposed to derive EBTs. However, they often produce comparable EBTs for the same endpoints.

Conclusion

In vitro bioassays are often used for water quality screening. Some of the most mature bioassays are ready to be employed for screening water samples for specific types of toxicity such as estrogens and AhR agonists. The use of bioassays can help to build public support by providing more comprehensive screening of unknown water constituents with endpoints based on human health relevance. In vitro bioassays cannot determine specific compounds responsible for observed bioactivity and are meant to augment, not replace, existing targeted instrumental assessments.

In vitro bioassays could be used for different purposes in water quality assessment, including comparing the quality of different water sources, the efficacy of treatment technologies, and the ultimate chemical quality of drinking water. It is important to reemphasize that in vitro bioassays should be considered as a step forward in more comprehensive water assessment rather than a panacea that will replace analytical monitoring and in vivo animal testing. While limitations surely do exist, in vitro bioassays greatly expand the ability to detect contaminants relevant to human and environmental health, and while these tools were still unable to determine whether water is "safe", their application will make water "safer".