- Title
- Toxicity of parabens and metal oxide nanoparticles (TiO₂ and ZnO) to human spermatozoa and earthworm reproduction
- Creator
- Samarasinghe Vidane Arachchige, Chamila
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2019
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Parabens and nanoparticles are used as additives in most of the consumer products. Increased use of the consumer products containing these compounds and their continuous release to the environment may lead to negative consequences in humans and organisms if these compounds possess any toxic potential. Parabens are commonly used in personal care products as a preservative. Metal oxide nanoparticles are also used in commercial products. The commonality between parabens, TiO₂ nanoparticles and ZnO nanoparticles is all these compounds are common additives in sunscreens, cosmetics, pharmaceuticals and foods. The endocrine disrupting effects of parabens and various characteristics of nanoparticles such as higher reactivity, ability to penetrate biological barriers (Blood-brain barrier, testis barrier) have risen global concerns on their environmental and public health hazards. Toxicity investigations using earthworms is a frequently used biomarker in terrestrial ecotoxicity assessments. There are many different measures for public health hazard assessments. Male reproductive health is one of the sensitive measures that can be used to predict the toxic effects of compounds on humans. To gain insight about the public health hazard of these compounds, the oxidative potential of parabens (methyl, propyl, and butylparaben) and nanoparticles TiO₂ anatase, rutile, and anatase/rutile mixture) to human spermatozoa was investigated. Then, the ecological hazard of parabens and metal oxide nanoparticles on earthworms were studied. In this study, acute and chronic toxicity of these compounds to adult earthworms was assessed. Nanoparticles, being a persistent and emerging pollutant in the terrestrial environment, were tested for their long term effects on lifecycle traits of juvenile earthworms. Parabens showed their potential to generate oxidative stress in human spermatozoa at the concentrations relevant to human use (Eg. methylparaben, at 13 mM, a concentration normally used as vaginal lubricants). None of the crystal types of TiO₂ nanoparticles used in this study showed oxidative stress against human spermatozoa at the environmentally relevant concentrations. Parabens were readily degraded in soil and did not cause acute or chronic toxicity to earthworms. Two soils with different characteristics were used in the nanoparticle toxicity assays. Upon a comparatively shorter exposure duration (28 days), both TiO₂ nanoparticles and ZnO nanoparticles did not show significant deleterious effects on the survival and reproductive outcome of adult earthworms. The exception was at high concentrations (500 and 1000 mg Kg⁻¹), where ZnO showed reproductive toxicity only in one soil. The toxicity mechanism was not clear. The juveniles born to these parent earthworms (F1 generation) were further exposed to TiO₂ anatase, TiO₂ rutile and ZnO nanoparticles (0.1 – 1000 mg Kg⁻¹) in two soils (same exposure, similar soil). The survival, growth, sexual maturity and the reproduction of these F1 individuals were observed over ≈ 10 months. The study showed that at lower concentrations (<10 mg Kg⁻¹), growth and sexual maturity of earthworms can be stimulated due to the exposure to anatase particles. At high doses (>100 mg Kg⁻¹ of anatase), earthworm reproduction is negatively affected. However, depending on the soil characteristics, these results may vary. A slight, non-significant growth retardation can be seen due to the exposure to TiO₂ rutile nanoparticles. Reproduction of earthworms was not inhibited by the TiO₂ rutile exposure. A significant growth retardation, delay in sexual maturity and reproductive inhibition were evidenced in F1 generation of earthworms upon ZnO nanoparticle exposure. These effects were observed from 1 mg Kg⁻¹ dose level. Our study shows the greater sensitivity of juveniles to these toxicants than that of adults earthworms. Further, this study demonstrates that there are transgenerational effects in earthworms due to metal oxide nanoparticle exposure. To the best of our knowledge, this is the first report on the long term toxicity of metal oxide nanoparticles to earthworms. The population responses to the toxic chemicals in the environment will provide more insight than at the individual level.
- Subject
- nanoparticles; parabens; toxicity; earthworm; spermatozoa
- Identifier
- http://hdl.handle.net/1959.13/1407519
- Identifier
- uon:35737
- Language
- eng
- Full Text
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