Anson North

Document Type


Date of Award



College of Science, Engineering, and Technology (COSET)

Degree Name

Ph.D. in Environmental Toxicology

Committee Chairperson

Fawzia Abdel-Rahman

Committee Member 1

Mahmoud Saleh

Committee Member 2

Bobby L Wilson

Committee Member 3

Hector C Miranda


• Biochemistry • Biology • Caenorhabditis elegans • Nematology • Toxicology


Azo dyes are dyes used to color textiles, paper, leather, plastics, foods, cosmetics, pharmaceuticals, brewed beverages, tattoo inks, printing inks, and more. They account for over 50% of all commercially used dyes produced annually and identified by aromatic rings connected by nitrogen-nitrogen double bonds (N=N). Azo dyes yield colorless aromatic amines and become potentially carcinogenic after biotransformation. Lipid-soluble azo dyes are the most toxic and some are banned for food usage, yet still detected at low concentrations in palm oils, chili powders, eggs, and other food products.

The nematode Caenorhabditis elegans (C. elegans) has been used in many environmental studies to determine the effects of toxicants. C. elegans are used as an effective model system for predicting human physiological response. The C. elegans genome is fully sequenced and is 60% homologous to humans. This study investigated the effects of lipid-soluble azo dyes on C. elegans. Three reproductive endpoints (brood size, egg-laying, and egg hatching), two behavioral endpoints (body bend frequency and pharyngeal pumping rate), and one enzymatic endpoint (reactive oxygen species [ROS]) were selected for the assessment of azo dye (Sudan I, Sudan II, Chrysoidine G, and Disperse Orange 3) toxicity.

Chrysoidine G and Disperse Orange 3 caused severe lifespan defects. Chrysoidine G, Sudan I, and Disperse Orange 3 exposure resulted in reproductive defects that significantly reduced brood size. Locomotion (body bends and tracks) and pharyngeal pumping were significantly impaired by Chrysoidine G, Sudan I, and Disperse Orange 3. The stress responses to azo dye exposure suggested severe toxicity. With endpoints of locomotion, pharyngeal pumping, reproduction, and ROS production, the toxicity of the examined azo dyes was: Chrysoidine G > Disperse Orange 3 > Sudan I > Sudan II. This study found that C. elegans exposed to sublethal concentrations of three (Chrysoidine G, Sudan I, and Disperse Orange 3) of the four azo dyes selected for this study resulted in deleterious and negative effects of multiple biological defects by affecting the life span, development, reproduction, locomotion and pharyngeal pumping behaviors.


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