Toxicity assessment of zebrafish following exposure to CdTe QDs.

CdTe quantum dots (QDs) are nanocrystals of unique composition and properties that have found many new commercial applications; therefore, their potential toxicity to aquatic organisms has become a hot research topic. The lab study was performed to determine the developmental and behavioral toxicities to zebrafish under continuous exposure to low concentrations of CdTe QDs (1-400 nM) coated with thioglycolic acid (TGA). The results show: (1) the 120 h LC(50) of 185.9 nM, (2) the lower hatch rate and body length, more malformations, and less heart beat and swimming speed of the exposed zebrafish, (3) the brief burst and a higher basal swimming rate of the exposed zebrafish larvae during a rapid transition from light-to-dark, and (4) the vascular hyperplasia, vascular bifurcation, vascular crossing and turbulence of the exposed FLI-1 transgenic zebrafish larvae.

Toxicity, uptake kinetics and behavior assessment in zebrafish embryos following exposure to perfluorooctanesulphonicacid (PFOS).

Perfluorooctanesulphonicacid (PFOS), a persistent organic contaminant, has been widely detected in the environment, wildlife and humans, but few studies have assessed its effect on aquatic organisms. The present study evaluated the effect of PFOS on zebrafish embryos. Zebrafish embryos exhibited developmental toxicity of bent spine, uninflated swim bladder, decreased heart rate and affected spontaneous movement after exposure to various PFOS concentrations (0-8mg/L) from 6 to 120h post-fertilization (hpf). The LC(50) at 120hpf was 2.20mg/L and the EC(50) at 120hpf was 1.12mg/L. Continuous exposure to PFOS from 1 to 121hpf resulted in a steady accumulation with no evidence of elimination. PFOS induced cell death at 24hpf was consistently found in the brain, eye, and tail region of embryos. PFOS exposure induced lesions in the muscle fibers with histological examination. Behavior assessment of PFOS in zebrafish embryos elevated the basal rate of swimming after 4 days of exposure, and larvae exposed to PFOS (0.25-4mg/L) for only 1h at 6dpf swam faster with increasing PFOS concentration. Embryos/larvae exposed to 8mg/L PFOS for 24h periods from 1 to 121hpf showed the highest incidence of malformations in the 97-121hpf window. This is the first study to define uptake kinetics and to focus on behavioral consequences following PFOS exposure in zebrafish. Our results further the understanding of the toxicity of PFOS to aquatic organisms and suggest the need for additional research to identify the mode of PFOS toxicity.

[Distribution of heavy metals in soils from the typical regions of Shantou and their environmental pollution assessment].

Distribution of Copper (Cu), Zinc (Zn), Nickel (Ni), Lead (Pb), Chromium (Cr), Cadmium (Cd), Arsenic (As), and Mercury (Hg) in soils from the typical regions of Shantou such as electrical wastes recycling sites were studied, and pollution risk of heavy metals on the environment was evaluated. Among the 118 surface soil samples, 42 (corresponding to 35.6%) were above the national standards when evaluated with single factor index method. Specifically, Ni, Cu, Hg, and As exceeded the standards by 26.3%, 18.6%, 7.6%, and 0.85%, respectively. Among the 20 samples from five section soil sites, 7 (corresponding to 35.0%) were above the national standards with Ni, Hg, and Cu exceeding respectively by 20.0%, 15.0%, and 10.0%. The composite pollution index of all samples ranged from 0.32 to 6.08, with an average of 1.26. Overall, 39.1% of soils were polluted, and which composed of heavily (7.2%), moderately (10.9%), and lightly (21.0%) contaminated soils. The highest composite pollution index (1.98) was found in Chaoyang district, followed with descending order by Jinping, Chenghai, Chaonan, Longhu, Haojiang districts, and Nanao town. Pollution, industrial and agricultural wastes, and contaminated irrigation water were the main sources of heavy metal contamination in soils. Except for Cr and As, concentrations of Cu, Pb, and Hg in soils from Shantou districts were much higher than the corresponding soil background concentrations recorded for Guangdong province, China, and the whole world. Controlling heavy metal output from industrial and agricultural sources and reducing the concentrations of soil heavy metals through integrated treatment techniques are the effective methods to improve the soil quality in Shantou.