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Influence of pH on the toxicity of nitrophenols to Microtox and Spirotox tests

Grzegorz Nałecz-Jawecki1, Józef Sawicki

  • 1Department of Environmental Health Sciences, University of Medicine, Banacha 1 street, 02-097, Warsaw, Poland. grzes@farm.amwaw.edu.pl

Chemosphere
|May 6, 2003
PubMed

Insights

Spirostomum ambiguum (Spirotox) is more sensitive to nitrophenols (NPs) than Vibrio fischeri (Microtox). Toxicity varies with pH, especially for dinitrophenols (DNPs), decreasing significantly as pH rises.

Area of Science:

  • Environmental toxicology
  • Ecotoxicology
  • Biomonitoring

Background:

  • Nitrophenols (NPs) are common environmental pollutants.
  • Assessing NP toxicity to aquatic organisms is crucial for environmental risk assessment.

Purpose of the Study:

  • To evaluate the toxicity of mononitrophenols and dinitrophenols (DNPs) to luminescent bacteria Vibrio fischeri (Microtox test) and ciliated protozoan Spirostomum ambiguum (Spirotox test).
  • To compare the sensitivity of Microtox and Spirotox assays for NP toxicity assessment.
  • To investigate the influence of pH on NP toxicity.

Main Methods:

  • Toxicity testing using Microtox (Vibrio fischeri) and Spirotox (Spirostomum ambiguum) assays.
  • Exposure of bioindicators to a range of mononitrophenols and dinitrophenols.
  • Varying the pH of the test medium to assess its impact on toxicity.

Main Results:

  • Spirotox assay demonstrated higher sensitivity to tested nitrophenols compared to the Microtox assay.
  • 2,5-Dinitrophenol (2,5-DNP) exhibited the highest toxicity, while 2-nitrophenol (2-NP) was the least toxic to both bioindicators.
  • Toxicity of dinitrophenols decreased significantly (over 20-fold) as pH increased from 6 to 8.
  • Mononitrophenol toxicity showed a moderate decrease (1.5 to 4-fold) with pH increase from 7 to 8.

Conclusions:

  • Spirostomum ambiguum is a more sensitive bioindicator for nitrophenol toxicity assessment than Vibrio fischeri.
  • pH is a critical factor influencing nitrophenol toxicity in aquatic environments, particularly for dinitrophenols.
  • The findings highlight the importance of considering environmental factors like pH in ecotoxicological risk assessments of nitrophenols.

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