Effect of nitrogen oxides and sulfur oxides to triphenyl phosphate degradation and cytotoxicity on surface of different transition metal salts.

Nitrogen oxides and sulfur oxides, as the dominant toxic gases in the atmosphere, can induce severe human health problems under the composite pollutant conditions. Currently the effect of nitrogen or sulfur oxides in atmospheric environment to the degradation and cytotoxicity of triphenyl phosphate (TPhP) on atmospheric particle surfaces still remain poorly understood. Hence, laboratory simulation methods were used in this study to investigate the effect and related mechanism. First, particle samples were prepared with the TPhP coated on MnSO4, CuSO4, FeSO4 and Fe2(SO4)3 surface. The results showed that, when nitrogen or sulfur oxides were present, more significant TPhP degradation on all samples can be observed under both light and dark conditions. The results proved nitrogen oxides and sulfur oxides were the vital influence factors to the degradation of TPhP, which mainly promoted the OH generation in the polluted atmosphere. The mechanism study indicated that diphenyl hydrogen phosphate (DPhP) and OH-DPhP were two main stable degradation products. These degradation products originated from the phenoxy bond cleavage and hydroxylation of TPhP caused by hydroxyl radicals. In addition, no TPhP related organosulfates (OSs) or organic nitrates (ON) formation were observed. Regarding the cytotoxicity, all the particles can induce more significant cellular injury and apoptosis of A549 cells, which may be relevant to the adsorbed nitrogen oxides or sulfur oxides on particles surfaces. The superfluous reactive oxygen species (ROS) generation was the possible reason of cytotoxicity. This research can supply a comprehensive understanding of the promoting effect of nitrogen and sulfur oxides to TPhP degradation and the composite cytotoxicity of atmospheric particles.

Degradation, transformation and cytotoxicity of triphenyl phosphate on surface of different transition metal salts in atmospheric environment.

Triphenyl phosphate (TPhP) and transition metal elements have been ubiquitously detected in the atmosphere, which can participate in atmospheric chemical reactions and induce damage to human health. Currently the understanding of TPhP degradation, transformation and cytotoxicity on atmospheric particles surface are still limited. Therefore, this study used laboratory simulation methods to investigate the influence of irradiation time, transition metal salts, relative humidity (RH) to TPhP degradation, transformation and relative cytotoxicity. TPhP was coated on particle surfaces of four transition metal salts (MnSO4, CuSO4, FeSO4 and Fe2(SO4)3) in the experiment. Within 12 h irradiation, the significant TPhP photodegradation can be observed on all particles surface. Among these influence factors, the irradiation and RH were the crucial aspects to TPhP degradation, which primarily affect the OH concentration in the atmosphere. The transition metal elements only exhibited slightly catalytic effect to TPhP degradation. The mechanism study indicated that the major degradation products of TPhP are diphenyl hydrogen phosphate (DPhP) and OH-DPhP, which originated from the phenoxy bond cleavage and hydroxylation of TPhP induced by OH. As for the cytotoxicity to A549 cells, all the transition metal particles coated with TPhP can cause cellular injury, which was chiefly induced by the transition metal salt. The possible cytotoxicity mechanism of these particles to A549 cells can be attributed to the excessive reactive oxygen species (ROS) production. This study may provide a further understanding of TPhP degradation and related cytotoxicity with the coexistent transition metal salts in the atmosphere.