Toxicity Of TiO2 Nanoparticles Research Articles

Respiratory toxicity of TiO2 nanoparticles after intravenous instillation: an experimental study.

Nanomaterials are materials consisting of particles having one or more dimensions smaller than 100 nm. Nanoparticles (NP) have different properties and effects in comparison with the same particle materials of larger size. They can penetrate through various membranes and get from the bloodstream to other organs in the body. Therefore, in our experiment we have dealt with the impact of nanoparticles TiO2 instilled intravenously (i.v.) (to a tail vein of an animal) on the selected parameters of bronchoalveolar lavage (BAL). The aim of our study was to determine whether TiO2 nanoparticles do pass through the vascular system to the respiratory tract, and if so, how they affect the selected inflammatory and cytotoxic parameters of bronchoalveolar lavage. Wistar rats were intravenously given a suspension of TiO2 nanoparticles in saline solution. This suspension contained 10% volume of rat serum in dose: 1.0% from LD50 = 0.592 mg/kg of animal body weight. After the time intervals 1, 7, 14 and 28 days, the animals were sacrificed under anaesthesia; bronchoalveolar lavage was performed and the BAL cells were isolated. We have examined these markers: differential count of BAL cells - alveolar macrophages (AM), polymorphonuclear leukocytes (PMNL), lymphocytes (Ly); viability and phagocytic activity of AM; proportion of immature cells and cathepsin D enzyme levels. Regarding the respiratory toxicity of TiO2 nanoparticles we have found that TiO2 nanoparticles are relatively inert. BAL examined parameters (except the immature form of AM) were not significantly changed after 28 days of instillation compared to the control group. We found that the TiO2 nanoparticles used in our study were transferred from the bloodstream to the respiratory tract, but in a 28-day phase after i.v. instillation have been largely eliminated by the defence mechanism from the respiratory tract. We suggest low biopersistence and relatively rapid elimination of TiO2 nanoparticles from the lung under used experimental conditions.

Effects of TiO2 Nanoparticles on the Neotropical Cladoceran Ceriodaphnia silvestrii by Waterborne and Dietary Routes

The impact of nanoparticles (NPs) in zooplankton is poorly studied, particularly when organisms are exposed through diet. Food, constituted mainly by unicellular algae, can act as an important route of contamination for zooplankton. Since unicellular algae have a high surface area in relation to their volume, NPs can interact with their cell membranes and walls, as well as with exopolysaccharides secreted by them. In the present research, we investigated both the acute effects of waterborne titanium dioxide nanoparticles (TiO2 NPs), and its chronic effects via dietary exposure on the Neotropical freshwater zooplankton Ceriodaphnia silvestrii Daday, 1902 (Crustacea: Cladocera). The observed acute effects served as support for chronic tests, in which we investigated the effects of TiO2 NPs on survival and life history parameters (body length, numbers of eggs, and neonates produced) of cladoceran adult females, using the freshwater cosmopolitan chlorophycean Raphidocelis subcapitata as source of contamination of TiO2 NPs for zooplankton. R. subcapitata cells were exposed to concentrations of 0, 0.01, 1, and 10 mg L−1 of TiO2 NPs for 96 h, and then provided as food for females of C. silvestrii until the third brood was released. Significant toxic effects were observed in body length and total number of neonates and eggs produced by females of C. silvestrii at concentrations of 1 and 10 mg L−1 of TiO2 NPs. Survival was the most sensitive parameter when exposure was given via food. From the concentration of 0.01 mg L−1 of TiO2 NPs, there was a decrease in the survival of C. silvestrii females. The quantification of TiO2 NPs in algae evidenced that they have retained NPs in their cells, being, therefore, an important route of exposure and toxicity of TiO2 NPs to the studied microcrustacean.

A review of cardiovascular toxicity of TiO2, ZnO and Ag nanoparticles (NPs).

To ensure the safe use of nanoparticles (NPs) in modern society, it is necessary and urgent to assess the potential toxicity of NPs. Cardiovascular system is required for the systemic distribution of NPs entering circulation. Therefore, the adverse cardiovascular effects of NPs have gained extensive research interests. Metal based NPs, such as TiO2, ZnO and Ag NPs, are among the most popular NPs found in commercially available products. They may also have potential applications in biomedicine, which could increase their contact with cardiovascular systems. This review aimed at providing an overview about the adverse cardiovascular effects of TiO2, ZnO and Ag NPs. We discussed about the bio-distribution of NPs following different exposure routes. We also discussed about the cardiovascular toxicity of TiO2, ZnO and Ag NPs as assessed by in vivo and in vitro models. The possible mechanisms and contribution of physicochemical properties of metal based NPs were also discussed.

Band Alignment-Driven Oxidative Injury to the Skin by Anatase/Rutile Mixed-Phase Titanium Dioxide Nanoparticles Under Sunlight Exposure

Anatase/rutile mixed-phase titanium dioxide (TiO2) nanoparticles (NPs) have been found in cosmetics and cotton textiles. Once exposed to sunlight, mixed-phase TiO2 NPs are even more toxic to cells than pure phase NPs; however, the underlying mechanism remains unclear. Considering the unique anatase/rutile heterojunction structure existing in mixed-phase NPs, the potent toxicity of mixed-phase TiO2 NPs probably originates from the high reactive oxygen species (ROS) production because the anatase/rutile heterojunction is constituted by the staggered energy bands that facilitate the electron-hole separation at the interface due to the band alignment. In the present study, a library of mixed-phase TiO2 NPs with different anatase/rutile ratios was established to investigate the potential property-activity relationship and further clarify the underlying molecular mechanism. Under sunlight exposure, these mixed-phase TiO2 NPs could produce significant abiotic ROS and induce hierarchical oxidative stress to HaCaT skin cells and mice skin. The ROS magnitude and toxicity potential of these NPs were found to be proportional to their energy band bending (BB) levels. This means that the toxicity of mixed-phase TiO2 NPs can be correlated to their heterojunction density, and the toxicity potential of mixed-phase TiO2 NPs can be weighed by their BB levels.

Protein profiling as early detection biomarkers for TiO2 nanoparticle toxicity in Daphnia magna.

The mode of action for nanoparticle (NP) toxicity in aquatic organisms is not yet fully understood. In this work, a strategy other than toxicity testing was applied to Daphnia magna exposed to TiO2-NPs: the use of nuclear microscopy and the assessment of protein profile. D. magna is a keystone species broadly used as a model system in ecotoxicology. Titanium (Ti) was found in the D. magna digestive tract, mainly in the gut. The penetration of Ti into the epithelial region was greater at higher exposure levels and also observed in eggs in the brood pouch. The protein profile of individuals exposed to different concentrations showed that 2.8 and 5.6 mg/L TiO2-NP concentrations induced an over-expression of the majority of proteins, in particular proteins with molecular weight of ∼120, 85 and 15 kDa, while 11.2 mg/L TiO2-NP had an inhibitory effect on protein expression. The Matrix-assisted laser desorption ionization with tandem time of flight mass spectrometry (MALDI-TOF/TOF MS) analysis of these proteins consistently identified them as vitellogenin (Vtg)-like proteins, associated with enzymes involved in redox balance. These results indicate that Vtg-like proteins are up-regulated in D. magna exposed to TiO2-NPs. Vitellogenesis is associated with the reproduction system, suggesting that TiO2-NP exposure can impair reproduction by affecting this process. The precise mode of action of TiO2-NPs is still unclear and the results from this study are a first attempt to identify specific proteins as potential markers of TiO2-NP toxicity in D. magna, providing useful information for future research.

Effects of surfactants on the combined toxicity of TiO2 nanoparticles and cadmium to Escherichia coli

The combined ecological toxicity of TiO2 nanoparticles (nano-TiO2) and heavy metals has been paid more attention. As the common pollutants in water environment, surfactants could affect the properties of nanoparticles and heavy metals, and thus further influence the combined toxicity of nano-TiO2 and heavy metals. In this study, the effects of sodium dodecyl benzene sulfonate (SDBS) and Tween 80 on the single and combined toxicities of Cd2+ and nano-TiO2 to Escherichia coli (E. coli) were examined, and the underlying influence mechanism was further discussed. The results showed both SDBS and Tween 80 enhanced the toxicity of Cd2+ to E. coli in varying degrees. The reaction of SDBS and Cd2+ could increase the outer membrane permeability and the bioavailability of Cd, while Tween 80 itself could enhance the outer membrane permeability. The combined toxicity of nano-TiO2 and Cd2+ to E. coli in absence of surfactant was antagonistic because of the adsorption of Cd2+ to nano-TiO2 particles. However, in the presence of SDBS, both SDBS and nano-TiO2 influenced the toxicity of Cd2+, and also SDBS could adsorb to nano-TiO2 by binding to Cd2+. The combined toxicity was reduced at Cd2+ lower than 4mg/L and enhanced at Cd2+ higher than 4mg/L under multiple interactions. Tween 80 enhanced the combined toxicity of nano-TiO2 and Cd2+ by increasing the outer membrane permeability. Our study firstly elucidated the effects of surfactants on the combined toxicity of nano-TiO2 and Cd2+ to bacteria, and the underlying influencing mechanism was proposed.

A comparative toxicity study of TiO2 nanoparticles in suspension and adherent culture under the dark condition

The present study focused on the different acute toxicity of TiO2 nanoparticles(TiO2 NPs) towards the bacteria in suspension culture and adherent culture under the dark conditions. The study investigated the bacteria toxicity with TiO2 NPs at different concentrations(1—2000 mg/L), sizes(10 nm, 35 nm) and specific surface areas in unit volume solution(0—224 m2/L) characterized by the cell viability, extracellular polymeric substances(EPS) release and biofilm formation. The bacteria in adherent culture was found to be more resistant against the toxicity of TiO2 NPs compared to that in suspension culture. An NP dose and surface area dependent(rather than the size) bacterial viability was observed in suspension culture, specifically the surface area positively correlated with the toxicity of TiO2 NPs. The size of TiO2 NPs, however, played a more critical role in toxicity of TiO2 NPs in adherent culture. Therefore, the surface area dependent toxicity of TiO2 NPs is a comprehensive parameter describing the dose and size dependent toxicity of TiO2 NPs. The electron microscopic(SEM, TEM, EDX) observations suggested the EPS release and biofilm formation, during aggregation of TiO2 NPs on the bacteria after 12 h cultivation in adherent culture under the dark condition. A possible toxic mechanism could be that “effective surface areas” that directly contact with the bacterial membrane greatly contributed to the toxicity of TiO2 NPs in both suspension culture and adherent culture. Therefore, as for the possible resistance mechanism, EPS secretion and subsequent biofilm formation may protect the bacteria against the toxicity of TiO2 NPs.

Morphological alterations induced by the exposure to TiO2 nanoparticles in primary cortical neuron cultures and in the brain of rats.

Nowadays, nanoparticles (NPs) of titanium dioxide (TiO2) are abundantly produced. TiO2 NPs are present in various food products, in paints, cosmetics, sunscreens and toothpastes. However, the toxicity of TiO2 NPs on the central nervous system has been poorly investigated until now. The aim of this study was to evaluate the toxicity of TiO2 NPs on the central nervous system in vitro and in vivo. In cell cultures derived from embryonic cortical brain of rats, a significant decrease in neuroblasts was observed after 24 to 96 h of incubation with TiO2 NPs (5 to 20 μg/ml). This phenomenon resulted from an inhibition of neuroblast proliferation and a concomitant increase in apoptosis. In the same time, a gliosis, characterized by an increase in proliferation of astrocytes and the hypertrophy of microglial cells, occurred. The phagocytosis of TiO2 NPs by microgliocytes was also observed. In vivo, after intraperitoneal injection, the TiO2 NPs reached the brain through the blood brain barrier and the nanoparticles promoted various histological injuries such as cellular lysis, neuronal apoptosis, and inflammation. A reduction of astrocyte population was observed in some brain area such as plexiform zone, cerebellum and subependymal area. An oxidative stress was also detected by immunohistochemistry in neurons of hippocampus, cerebellum and in subependymal area. In conclusion, our study demonstrated clearly the toxic impact of TiO2 NPs on rat brain and neuronal cells and pointed about not yet referenced toxicity impacts of TiO2 such as the reduction of neuroblast proliferation both in vitro and in vivo.

Is Exposure to Titanium Dioxide Nanoparticle Associated with Occupational Lung Cancer among Titanium Dioxide Production Workers? An Emerging Issue

This systemic literature review was conducted to find out if there was an association between exposure to TiO2 NP (Titanium dioxide nanoparticle) and occupational lung cancer among TiO2 production workers. An electronic database search was employed which generated several studies relating to TiO2 nanoparticle toxicity. From these studies only ten (10) articles were chosen for this study because they met the review criteria. Two articles were centered around cohort study design while other 8 studies were on experimental design. The two cohort studies did answer the review question that showed no association of TiO2 toxicity and respiratory diseases while the experimental design studies produced conflicting results. The conflicting results were attributed to their objective, sample size, and the study designs. Despite the different conclusions there is adequate evidence in the experimental studies that demonstrated evidence of TiO2 nanoparticle toxicity. Notable cases include cytotoxicity, genotoxicity, apoptotic and cell necrosis in rat and human cells exposed to TiO2 which is generally dose response related. The strengths and limitations of the 10 studies are also discussed. General understanding gained from these studies is for appropriate agencies to be proactive in developing mitigation and controls measures against nanoparticle exposure. This is necessary to avert repetition of previous experiences with exposure to asbestos fibers as a point of reference.

Ocean acidification increases the toxic effects of TiO2 nanoparticles on the marine microalga Chlorella vulgaris

Concerns about the environmental effects of engineered nanoparticles (NPs) on marine ecosystems are increasing. Meanwhile, ocean acidification (OA) has become a global environmental problem. However, the combined effects of NPs and OA on marine organisms are still not well understood. In this study, we investigated the effects of OA (pH values of 7.77 and 7.47) on the bioavailability and toxicity of TiO2 NPs to the marine microalga Chlorella vulgaris. The results showed that OA enhanced the growth inhibition of algal cells caused by TiO2 NPs. We observed synergistic interactive effects of pH and TiO2 NPs on oxidative stress, indicating that OA significantly increased the oxidative damage of TiO2 NPs on the algal cells. Importantly, the elevated toxicity of TiO2 NPs associated with OA could be explained by the enhanced internalization of NPs in algal cells, which was attributed to the slighter aggregation and more suspended particles in acidified seawater. Overall, these findings provide useful information on marine environmental risk assessments of NPs under near future OA conditions.

Toxicity of TiO2 nanoparticles on the NRK52E renal cell line

Titanium dioxide nanoparticles are widely used in industry to produce a number of products (cosmetics, paints, foods). TiO2 nanoparticles form aggregates and their toxicity varies in function of their size. In this study, aggregate sizes were determined using dynamic light scattering (DLS). The stability of the suspension was evaluated by turbidimetry and the size by transmission electronic microscopy (TEM). In the present study the toxicity of TiO2 nanoparticles was evaluated in vitro on rat kidney proximal tubular cells (NRK-52E). Cells were exposed to TiO2 nanoparticles (20 μg/mL) for 24, 48, 72 and 96 hours. TiO2 nanoparticles induce the production of reactive oxygen species (ROS). The relative number of mitosis decreased, while an increase of apoptotic cells was noted. The number of S-phase cells evidenced by BrdU immunoreactivity in cultures was significantly reduced by the exposure to the nanoparticles. These results attest to the toxic effect of the TiO2 nanoparticles on NRK-52E cells.

Distinct toxic interactions of TiO2 nanoparticles with four coexisting organochlorine contaminants on algae

Engineered nanoparticles are increasingly discharged into the environment. After discharge, these nanoparticles can interact with co-existing organic contaminants, resulting in a phenomena referred to as ‘joint toxicity’. This study evaluated joint toxicities of TiO2 nanoparticles (TiO2NPs) with four different (atrazine, hexachlorobenzene, pentachlorobenzene, and 3,3′,4,4′-tetrachlorobiphenyl) organochlorine contaminants (OCs) toward algae (Chlorella pyrenoidosa). The potential mechanisms underlying the joint toxicity were discussed, including TiO2NPs–OC interactions, effects of TiO2NPs and OCs on biophysicochemical properties of algae and effects of TiO2NPs and OCs on each other’s bioaccumulation in algae. The results indicate that coexposure led to a synergistic effect on the joint toxicity for TiO2NPs–atrazine, antagonistic effect for TiO2NPs–hexachlorobenzene and TiO2NPs–3,3',4,4'-tetrachlorobiphenyl, and an additive effect for TiO2NPs–pentachlorobenzene. There was nearly no adsorption of OCs by TiO2NPs, and the physicochemical properties of TiO2NPs were largely unaltered by the presence of OCs. However, both OCs and NPs affected the biophysicochemical properties of algal cells and thereby influenced the cell surface binding and/or internalization. TiO2NPs significantly increased the bioaccumulation of each OC. However, with the exception of atrazine, the bioaccumulation of TiO2NPs decreased when used with each OC. The distinct joint toxicity outcomes were a result of the balance between the increased toxicities of OCs (increased bioaccumulations) and the altered toxicity of TiO2NPs (bioaccumulation can either increase or decrease). These results can significantly improve our understanding of the potential environmental risks associated with NPs.

A two-step model of TiO2 nanoparticle toxicity in human liver tissue

We examine the toxicity of titanium dioxide (TiO2) nanoparticles on human liver through a two-step approach, including a physiologically-based pharmacokinetic (PBPK) model and a cell-response model. The PBPK model predicts the bio-distribution of nanoparticles that remain in the human body after exposure, with special attention to their accumulation in liver tissue. The cell-response model predicts liver cell death as a consequence of the accumulated TiO2 nanoparticles by considering cell fate dynamics through the interplay between cellular uptake of the nanoparticles and their dilution due to cell division. The results suggest that tissue damage from a low nanoparticle dose is negligible due to renewal cell division, but for higher doses larger fractions of cells must participate in the cell cycle to recover the original tissue mass. By combining the two models, it becomes possible to explain the liver cell viability and cell death after TiO2 nanoparticle exposure.

Oxidative stress mediated toxicity of TiO2 nanoparticles after a concentration and time dependent exposure of the aquatic macrophyte Hydrilla verticillata

The present study focused on oxidative stress effects in the aquatic macrophyte Hydrilla verticillata after exposure to titanium dioxide nanoparticles (TiO2-NPs). Experiments were conducted with different TiO2-NPs and concentrations (0.1 mg/L and 10 mg/L) in a time-dependent manner (0 h, 24 h, 48 h, 96 h, 168 h). To assess various levels of the oxidative stress response in H. verticillata, the level of hydrogen peroxide (H2O2), the ratio of reduced to oxidized glutathione (GSH/GSSG), and activities of the antioxidative enzymes catalase (CAT) and glutathione reductase (GR) were evaluated. Study results imply oxidative stress effects after TiO2-NP exposure as adaptations in plant metabolism became apparent to counteract increased ROS formation. All TiO2-NPs caused elevated activities of the enzymes CAT and GR. Moreover, decreased ratios of GSH/GSSG indicated an activation of GSH-dependent pathways counteracting ROS formation. Plants exposed to a bulk-sized control revealed a size-dependent influence on the antioxidative stress response. As H2O2 level increases were solely detected after exposure to 10 mg/L TiO2-NPs and nano-exposed plants showed normalization in its antioxidative stress response after 168h of exposure, it can be suggested that macrophytes are able to cope with currently predicted low-level exposures to TiO2-NPs.

Effect of titanium dioxide nanoparticles on male and female reproductive systems

Titanium Dioxide (TiO2) nanoparticle has a wide range of application in industrial and consumer products especially in cosmetics such as high sun protection factor creams in order to protect the skin from UV light. In spite of its increased production and use there is not enough epidemiological data regarding TiO2 nanoparticle toxicity. Toxic effects of TiO 2 nanoparticles on human reproductive systems have been investigated by many studies mostly by employing animal models, but results are extremely conflicted and inconsistent. In this review we summarized published data about the effects of TiO2 nanoparticle on male and female reproductive systems to clarify its possible toxic effects on reproduction and fertility.

Titanium dioxide aggregating nanoparticles induce autophagy and under-expression of microRNA 21 and 30a in A549 cell line: A comparative study with cobalt(II, III) oxide nanoparticles

The toxicity of TiO2 nanoparticles (NPs) is controversial, while it is widely accepted for Co3O4 NPs. We present a comparative study concerning the uptake of these NPs and their effect on cytoplasmic organelles and autophagy in a human lung carcinoma cell line (A549), including assays on the expression of autophagy-related microRNAs. The NP accumulation caused a fast dose- and time-dependent change of flow cytometry physical parameters particularly after TiO2 NP exposure. The intracellular levels of metals confirmed it, but the Co concentration was ten times higher than that of Ti. Both NPs caused neither necrosis nor apoptosis, but cytotoxicity was mainly evident for Co3O4 NPs in the first 72h. TiO2 NPs caused autophagy, contrarily to Co3O4 NPs. Furthermore, a significant and persistent downregulation of miRNA-21 and miRNA-30a was observed only in TiO2 NPs-treated cultures. The expression of miRNA-155 was similar for both NPs. Oxidative stress was evident only for Co3O4 NPs, while both NPs perturbed endoplasmic reticulum and p-53 expression. In conclusion, the oxidative stress caused by Co3O4 NPs can influence energy homeostasis and hamper the ability to detoxify and to repair the resulting damage, thus preventing the induction of autophagy, while TiO2 NPs elicit autophagy also under sub-toxic conditions.

Accelerated ecotoxicity of photoreactive nanoparticles on Moina macrocopa.

Zinc oxide nanoparticles (ZnO NPs) and titanium dioxide nanoparticles (TiO2 NPs) are well known as photoreactive nanoparticles (NPs). Various phototoxicities of ZnO NPs and TiO2 NPs were reported on several organisms. It was still necessary to evaluate the toxicity of photoreactive ZnO NPs and TiO2 NPs due to species-specific effects under various irradiation conditions. We compared the acute toxicity of Moina macrocopa under visible, ultraviolet (UV) A, and B irradiations, according to the Organization for Economic Cooperation and Development guidelines for the testing of chemicals (Test No. 202). The sensitivity of ZnO NPs for M. macrocopa was UVB>UVA>visible light irradiation. There were no significant lethal and immobile effects of TiO2 NPs on juveniles under all irradiations and in the tested concentrations of TiO2 NPs. Photoreactive NPs have a potential and accelerated toxicity on organisms in the ambient environments.

Toxicity of TiO2 nanoparticles on soil nitrification at environmentally relevant concentrations: Lack of classical dose–response relationships

Titanium-dioxide nanoparticles (TiO2-NPs) are increasingly released in agricultural soils through, e.g. biosolids, irrigation or nanoagrochemicals. Soils are submitted to a wide range of concentrations of TiO2-NPs depending on the type of exposure. However, most studies have assessed the effects of unrealistically high concentrations, and the dose–response relationships are not well characterized for soil microbial communities. Here, using soil microcosms, we assessed the impact of TiO2-NPs at concentrations ranging from 0.05 to 500 mg kg−1 dry-soil, on the activity and abundance of ammonia-oxidizing archaea (AOA) and bacteria (AOB), and nitrite-oxidizing bacteria (Nitrobacter and Nitrospira). In addition, aggregation and oxidative potential of TiO2-NPs were measured in the spiking suspensions, as they can be important drivers of TiO2-NPs toxicity. After 90 days of exposure, non-classical dose–response relationships were observed for nitrifier abundance or activity, making threshold concentrations impossible to compute. Indeed, AOA abundance was reduced by 40% by TiO2-NPs whatever the concentration, while Nitrospira was never affected. Moreover, AOB and Nitrobacter abundances were decreased mainly at intermediate concentrations nitrification was reduced by 25% at the lowest (0.05 mg kg−1) and the highest (100 and 500 mg kg−1) TiO2-NPs concentrations. Path analyses indicated that TiO2-NPs affected nitrification through an effect on the specific activity of nitrifiers, in addition to indirect effects on nitrifier abundances. Altogether these results point out the need to include very low concentrations of NPs in soil toxicological studies, and the lack of relevance of classical dose–response tests and ecotoxicological dose metrics (EC50, IC50…) for TiO2-NPs impact on soil microorganisms.

Dependence of the irradiation conditions and crystalline phases of TiO2 nanoparticles on their toxicity to Daphnia magna

Crystalline phases and irradiation conditions played critical roles in the oxidative stress-related toxicity of TiO2 nanoparticles to Daphnia magna.

Comparative study on toxicity of ZnO and TiO2 nanoparticles on Artemia salina: effect of pre-UV-A and visible light irradiation.

This study evaluated the toxicity potential of ZnO and TiO2 nanoparticles under pre-UV-A irradiation and visible light condition on Artemia salina. The nanoparticle suspension was prepared in seawater medium and exposed under pre-UV-A (0.23mW/cm2) and visible light (0.18mW/cm2) conditions. The aggregation profiles of both nanoparticles (NPs) and dissolution of ZnO NPs under both irradiation conditions at various kinetic intervals (1, 24, 48h) were studied. The 48-h LC50 values were found to be 27.62 and 71.63mg/L for ZnO NPs and 117 and 120.9mg/L for TiO2 NPs under pre-UV-A and visible light conditions. ZnO NPs were found to be more toxic to A. salina as compared to TiO2 NPs. The enhanced toxicity was observed under pre-UV-A-irradiated ZnO NPs, signifying its phototoxicity. Accumulation of ZnO and TiO2 NPs into A. salina depends on the concentration of particles and type irradiations. Elimination of accumulated nanoparticles was also evident under both irradiation conditions. Other than ZnO NPs, the dissolved Zn2+ also had a significant effect on toxicity and accumulation in A. salina. Increased catalase (CAT) activity in A. salina indicates the generation of oxidative stress due to NP interaction. Thus, this study provides an understanding of the toxicity of photoreactive ZnO and TiO2 NPs as related to the effects of pre-UV-A and visible light irradiation.