The chlorophyll fluorescence (CF) assay is recognized as an important tool for monitoring the electron transport system of photosynthesis. The increase or decrease of fluorescence, compared to control, can indicate a lesion in the chain of events in photosynthesis or damage to the chloroplasts. Inhibition of photosynthesis in leaf segments of Tradescantia by herbicides (glyphosate, picloram & 2,4-D, triclopyr and hexazinone), heavy metals (Zn, Cu, Cd), a surfactant (sodium lauryl sulfate), and sodium fluoride (NaF) has been demonstrated using this method. The strongest changes of fluorescence induction curves were caused by hexazinone. Photosynthetic inhibition was observed as an increase in initial fluorescence (Fo) and a decrease in variable fluorescence (Fv) and electron pool size (EP). A CF assay predicted herbicidal injury in Tradescantia leaves at least 24 h before leaf necrosis appeared. Three heavy metals (Zn, Cu, Cd) are known as strong respiration and photosynthetic inhibitors in plant cells. In this study cadmium chloride, at the highest concentration (1000 ppm) tested, caused the strongest changes in Fv and EP size, which are characteristics of Photosystem II (PS II) photochemistry. Phytotoxicity of NaF caused an increase in Fv and EP compared to the control.
The mutagenicity of the vicinity of an oil-refining complex and a petrochemical complex was examined using the germinal revertant frequency of Zea mays waxy-C W22 and the somatic stamen hair system of Tradescantia. A 3-year study was conducted at Wood River, Illinois, in 1978, 1979, and 1980, and a 1-year study in 1979 at Beaumont, Texas. The studies conducted in 1978 registered the effects of airborne pollutants and possible soil pollutants. The studies in 1979 and 1980 registered only the effects of airborne pollutants. Elevated mutation frequencies of Zea mays compared to various controls occurred in 1978, 1979, and 1980 at both complexes. The mutation frequencies of Zea mays were particularly high, up to 26-times control values. By contrast, the mutation frequencies of Tradescantia were much lower, with maximum mutation frequencies five times control value.
Bioassays utilizing the green alga Selenastrum capricornutum were performed on filtered eluates from soil treated with six commonly used forestry herbicides applied at labelrecommended rates. The bioassays were conducted at three time periods after herbicide application—one hour, five days, and ten days. The 96-h EC50 values indicated growth inhibition (relative to control sample) for all treatments when assayed 1 h after herbicide application. Algal EC50 values of +100 (Control), +27.3 (Roundup™), -20.4 (Arsenal™ [2 lb Acid Equivalent] [AE]/gal), -22.4 (Garlon™ 4), -49.4 (Tordon 101M™), -100 (Velpar L™), and -100 (Velpar ULW™) were obtained. Assays conducted ten days after herbicide application to soil revealed substantially reduced toxicity of two herbicides. The 96-h EC50 values for Roundup and Arsenal were both +100. There was a significant enhancement effect observed with Roundup. A slight reduction in toxicity was noted for Garlon 4 (-15.9) and Tordon 101M (+9.9). No change in toxicity occurred for Velpar L or Velpar ULW. The herbicides were also applied to water and the following 96-h EC50 values in μg/ml were obtained: 5500 (Arsenal [2 lb AE]), 5300 (Arsenal [4 lb AE]), 5000 (Tordon 101M), 5000 (Garlon 4), 2600 (Roundup), 2.5 (Velpar L), and 1.2 (Velpar ULW).
The potential impact of the environmental pollutants on human health can be evaluated by the laboratory analysis of the environmental samples or by the measurement of the biological effects on indigenous populations and/or specific test organisms placed in the environment to be monitored. A canary in a cage, used by 19th century miners as a biological indicator for rising levels of toxic gases, is a classical example of in situ hazard identification. The induced toxic effects are often the result of synergistic and antagonistic interactions among various physical and chemical factors that are difficult to reproduce in the laboratory. Therefore, conceivably the biological effects measured on or near the impacted site have greater relevancy for hazard assessment to man than from the data derived from the environmental samples analyzed in the lab. The organisms most commonly employed for the assessment of mutagenicity under real-world conditions are: (1) flowering plants, (2) wild and captive mammals, and (3) aquatic vertebrates. Plant species such as Tradescantia paludosa, Zea mays, and Osmunda regalis have been used for monitoring ambient air quality around several major industrial cities in the U.S.A., nuclear power plants, and industrial waste sites, and also for the assessment of potential health effects of municipal sewage sludges. Domestic animals such as dogs can be used as sentinels to provide information on the effects of contaminants in the environment and have been used to a limited extent to evaluate the environmental influences on the occurrence of breast cancer and osteosarcoma. Cytogenetic analysis from feral and wild animals has been employed for assessing the health hazards and prioritizing the clean-up efforts at hazardous waste sites. Aquatic animals have been used more often than terrestrial animals or plants to identify and characterize the genotoxic effects of environmental pollution. Since 1970, a number of studies has been reported on the mutagenic and neoplastic effects on aquatic animals from coastal areas and continental rivers, lakes, and ponds. The limitations of in situ environmental assessment are lack of control over the physical environmental components, inherent variability and interactions of test organisms, lack of control of exposure doses, and difficulty of finding concurrent experimental controls. Nevertheless, flowering plants, terrestrial, and aquatic animals may serve as useful sentinels and biomarkers of environmental pollution.
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