Toxicity Of Polyaromatic Hydrocarbons Research Articles

Polyaromatic hydrocarbons in biochars and human health risks of food crops grown in biochar-amended soils: A synthesis study

Soil amendment with biochars is currently being studied worldwide as a sustainable agricultural practice to improve soil and water quality, increase crop productivity, and augment soil carbon storage. However, the formation of polyaromatic hydrocarbons (PAHs) during biochar production is inevitable. Therefore, it is crucial to assess the risks in food safety and human health of crops grown in biochar-amended soils. This paper performed a synthesis study of PAH concentrations in biochars and estimated the risks of soils amended with biochars, based on refereed articles published between 2012 and 2018. The PAH concentrations in biochars ranged greatly, with the dominant proportion being 2–3 ringed PAHs (40%–71%). Biochar application increased the PAH levels in soils at drastically varying extents (0.02–3574 μg/kg), which led to a broad range of PAH concentrations in food crops grown in biochar-amended soils. A five-step method was then introduced to assess the toxicity of biochar-borne PAHs to human health. The total mean incremental lifetime cancer risk for adults was estimated to range between 2.0 × 10−6–1.9 × 10−5 via direct contact with and ingestion (inhalation) of contaminated soils or consumption of tainted crops. These results indicated that biochar amendment in soils might pose potential risks to food safety and human health, but the overall cancer risks through exposure to biochar-borne PAHs in soils and food crops were low. Higher application rates (e.g. ≥20 t/ha) of biochars with high PAH contents can be avoided to minimize human cancer risks. Although biochar application in arable farmlands has many environmental and agronomic benefits, holistic and systematic approaches are required to fully assess the benefits and risks before their large-scale adoption. PAHs in biochar may be reduced by improving the biochar production process and developing a cost-effective post-manufacturing treatment.

Preliminary study of phytoremediation of brownfield soil contaminated by PAHs

Our project was aimed at improving a brownfield in the city of Kladno, where an old steel producing facility used to be in operation. Ecological risk is mainly caused by the processing of co-products during coal production (tars, oils). Knowledge of toxicology and environmental aspects can help us protect human health and the environment.Primarily, we focused on soil sampling and identification of pollutants. Results showed that organic contamination on the site is very high. Average concentration of total petroleum carbon in the soil was about 13g/kg DW, which is much more than the maximum allowed concentration. For selection of suitable plant species for phytoremediation at the site, experiments were conducted in a greenhouse. Biomass growth, root morphology, and pigment content in the leaves of Brassica napus var. Opus-C1 and Sorghum×drummondii var. Honey Graze BMR plants were studied. Plant analysis confirmed that polyaromatic hydrocarbons (PAHs) accumulated in the shoots of both plant species. B. napus plants grown on Poldi soil in a greenhouse were able to survive the toxicity of PAHs in soil, and their ability to accumulate PAHs from soil was evident. However, more studies are needed to decide if the plants are usable for phytoremediation of this brownfield.

Toxicity evaluation of five polyaromatic hydrocarbons to Escherichia coli using microcalorimetry and QASRs

The toxicity of five polyaromatic hydrocarbons (PAHs) to metabolism of Escherichia coli (E. coli) was evaluated with key parameters, including growth constant (k) and inhibitory ratio (I) from microcalorimetry analysis. The results showed that the toxicity followed pyrene > 9-phenanthrol > phenanthrene > 3-phenanthrenecarboxylic acid > naphthalene for the chemicals tested. Basing on physical and chemical parameters of these five PAHs, the quantitative structure–activity relationships (QASRs) equation was established by multiple linear regression analysis, indicating that narcosis, a non-specific and non-reactive toxic action, plays the predominant role in toxicity of these five PAHs to bacterial cells. This study illustrates that the toxicity of PAHs are determined by the number of the aromatic ring and the substituent groups, higher toxicity associated with the higher number of the aromatic rings.

Interactive effects of PAHs and heavy metal mixtures on oxidative stress in Chlorella sp. MM3 as determined by artificial neural network and genetic algorithm

Mixture toxicity studies are very complex due to the complexity exhibited by the chemicals involved, and the net interaction effects are highly dependent on mixture combinations, exposure dose and the test organism. For assessing the toxicity of mixtures, factorial analysis has been widely used, while the usage of models developed by artificial neural network (ANN) analysis and genetic algorithm (GA) is very limited. We combined for the first time the factorial design experiment with ANN and GA to develop a model for predicting the interactive toxicological effects using a soil microalga, Chlorella sp. MM3. The chemicals included in the mixtures were two polyaromatic hydrocarbons (PAHs), phenanthrene and benzo[a]pyrene, and two heavy metals (HMs), cadmium and lead. Three biochemicals implicated in oxidative stress, viz., malondialdehyde (a measure for lipid peroxidation, LPO), catalase activity and proline accumulation were used as the toxicity criteria. Validation of the predicted results related to the biochemicals with the experimental data clearly indicated that the model developed with the combination of ANN and GA is greatly effective in predicting the toxicity of PAHs and HMs mixtures toward microalga with <10% relative error. Both catalase and LPO were found to be the promising biomarkers for predicting microalgal toxicity of PAHs and HMs mixtures. In addition, a significant positive correlation was evident between the removal of PAHs/uptake of HMs and LPO.

Determination the Toxicity of Poly Aromatic Hydrocarbons Using HPLC in Diyala River Sediments

In this paper sixteen Polycyclic Aromatic Hydrocarbons (PAHs) are estimated in sediments in five locations along Diyala River where entering Baghdad city until flows into Tigris River, (PAHs) are organic compounds that contain two or more fused rings. Some of these compounds are classified as carcinogenic and mutagenic pollutants. Soxhlet technique is used in this work to extract PAHs from sediment samples with using methylene chloride as extraction solvent. High Performance Liquid Chromatography (HPLC) with UV-Vis detector is used for determination of PAHs. According to the results the maximum of total PAHs concentration in the sediment are found in the location No. 4 with1213.02mg/kg in summer and 283.17 mg/kg in winter, while the minimum of total PAHs concentration are found in location No. 1 with 46.42 mg/kg in summer and 16.70 mg/kg in winter. Locations numbers two three and five record values of total PAHs concentration with (148.35, 570.41 and 958.20 mg/kg) respectively in summer and (55.69, 100.47 and 171.55 mg/kg) respectively in winter. Naphthalene, Fluorene, Anthracene and Fluoranthene are the most dominant compounds in summer, while Benzo [k] fluoranthene, Benzo [a] pyrene, Benzo [ghi] perylene, Dibenz [a,h] anthracene and Indino [123cd] pyreneare the least compounds presence in all sites.

The use of quantum-chemical descriptors for predicting the photoinduced toxicity of PAHs

The geometries of 19 polyaromatic hydrocarbons (PAHs) were fully optimized and calculated by a density functional method (B3LYP) with the 3-21G basis set. Various quantum chemical descriptors such as the energy of the highest occupied molecular orbital (E (HOMO)), the energy of the lowest unoccupied molecular orbital (E (LUMO)), the difference in energy between those orbitals (E (GAP)), electronegativity (χ), chemical potential (μ), chemical hardness (η), softness index (S), electrophilicity (ω), and polarizability (α) were employed along with physicochemical descriptors to construct useful quantitative structure-activity relationship (QSAR) models for the photoinduced toxicity of PAHs toward two aquatic species (Daphnia magna and Scenedesmus vacuolatus). E (LUMO), E (HOMO), E (GAP), S, χ, the molar refractivity (MR), and the molecular weight provide valuable information and play a significant role in the assessment of PAH phototoxicity. The resulting models are not expected to be useful per se for making genuine predictions for much larger test sets, but the various results do demonstrate the potential benefits of incorporating quantum-chemical descriptors into QSAR models for predicting the phototoxicity of PAHs.