Ingestion and Dermal Cancer Risk via Exposure to Polycyclic Aromatic Hydrocarbon-Contaminated Soils in an Oil-Producing Community, Niger Delta, Nigeria

Microbes and microbial strategies in carcinogenic polycyclic aromatic hydrocarbons remediation: a systematic review

Degradation, detoxification, or removal of the omnipresent polycyclic aromatic hydrocarbons (PAHs) from the ecosphere as well as their prevention from entering into food chain has never appeared simple. In this context, cost-effective, eco-friendly, and sustainable solutions like microbe-mediated strategies have been adopted worldwide. With this connection, measures have been taken by multifarious modes of microbial remedial strategies, i.e., enzymatic degradation, biofilm and biosurfactant production, application of biochar-immobilized microbes, lactic acid bacteria, rhizospheric-phyllospheric-endophytic microorganisms, genetically engineered microorganisms, and bioelectrochemical techniques like microbial fuel cell. In this review, a nine-way directional approach which is based on the microbial resources reported over the last couple of decades has been described. Fungi were found to be the most dominant taxa among the CPAH-degrading microbial community constituting 52.2%, while bacteria, algae, and yeasts occupied 37.4%, 9.1%, and 1.3%, respectively. In addition to these, category-wise CPAH degrading efficiencies of each microbial taxon, consortium-based applications, CPAH degradation-related molecular tools, and factors affecting CPAH degradation are the other important aspects of this review in light of their appropriate selection and application in the PAH-contaminated environment for better human-health management in order to achieve a sustainable ecosystem.

Spatial distribution and risk assessment of polycyclic aromatic hydrocarbons in soils from contaminated sites in Eastern China

A total of 16 polycyclic aromatic hydrocarbons (PAHs) were measured in 28 soil column samples from two contaminated industrial sites in Eastern China. The total concentration of 16 PAHs (∑PAHs) in the surface soil (0-20 cm) was measured up to 52,600 ng/g (dry weight basis) with a remarkable spatial difference in the studied contaminated sites. The concentrations of the ∑PAHs in soils decreased with the increase in soil depth (0-10 m). The surface and subsurface soil presented a tenfold higher concentration than the soil with depth greater than 4 m. Additionally, the vertical migration tendency of the PAHs was found to be correlated significantly with their hydrophobicity (R2 = 0.79, P < 0.01). Naphthalene (with lowest octanol-water partition coefficient among the studied PAHs) showed the greatest average soil depth at which its peak concentration occurred. Furthermore, risk quotient analysis by using benzo[a]pyrene as reference compound showed that 71.4% of the samples exhibited high ecological risk for soil. Moreover, the total carcinogenic risk of the PAHs in the surface soil samples was assessed at 5.61 × 10-5-1.28 × 10-4 and 4.41 × 10-6-9.43 × 10-5 for male and female workers, respectively, in which 67.9%-71.4% of the samples showed potential risk. Generally, these results suggest a further consideration of ecological and health risks associated with PAHs in contaminated sites in Eastern China.

An integrated investigation of hydrocarbon pollution in Ahoada area, Niger Delta Region, Nigeria

This study investigates hydrocarbon pollution in the Ahoada community of the Niger Delta region of Nigeria. The study uses a geographic information system (GIS) for mapping oil spill hotspots in the region. The resistivity method was used to delineate the extent of hydrocarbon pollution to a depth of 19.7 m in the Ahoada area of the region. Three categories of soil samples, impacted soil (IMS), remediated soil (RS), and control soil (CS), were collected and analyzed for the presence of BTEX, PAH, TPH, TOC, and TOG. The concentrations of the samples from the IMS and RS were compared to that of the CS to determine the extent of pollution. The GIS mapping shows that the most polluted areas in the Niger Delta Region are Rivers, Bayelsa, and Delta states. Results of the geophysical images revealed contaminants' presence to depths beyond 20 m at some locations in the study area. The highest depth of contaminant travel was at Ukperede. Soil samples' analysis showed that the range of concentrations of TPH in IMS at Oshie was 17.27-58.36 mg/kg; RS was 11.73-50.78 mg/kg which were higher than the concentrations of 0.68 mg/kg in the CS. PAHs are more prevalent in Ukperede, ranging from 54.56 to 77.54 mg/kg. BTEX concentrations ranged from 0.02 to 0.38 mg/kg for IMP and 0.01-2.7 mg/kg for RS against a CS value of 0.01 mg/kg. The study revealed that there are characteristically high resistivity values in the samples which were corroborated by the findings from the resistivity survey. TOC was found to be higher in the IMS and RS than in the CS, demonstrating that a significant quantity of the hydrocarbon has undergone appreciable decomposition.

Aryl hydrocarbon receptor-kynurenine axis promotes oncogenic activity in BCP-ALL

B-cell precursor acute lymphoblastic leukemia (BCP-ALL), the most common childhood cancer, originates from lymphoid precursor cells in bone marrow committed to the B-cell lineage. Environmental factors and genetic abnormalities disturb the normal maturation of these precursor cells, promoting the formation of leukemia cells and suppressing normal hematopoiesis. The underlying mechanisms of progression are unclear, but BCP-ALL incidence seems to be increasing in parallel with the adoption of modern lifestyles. This study hypothesized that air pollution and haze are risk factors for BCP-ALL progression. The current study revealed that indeno(1,2,3-cd)pyrene (IP), a major component of polycyclic aromatic hydrocarbons (PAHs) in air, promotes oncogenic activities (proliferation, transformation, and disease relapse) in vitro and in vivo. Mechanistically, IP treatment activated the aryl hydrocarbon receptor (AHR)-indoleamine-2,3-dioxygenase (IDOs) axis, thereby enhancing tryptophan metabolism and kynurenine (KYN) level and consequent promoting the KYN-AHR feedback loop. IP treatment decreased the time to disease relapse and increased the BCP-ALL cell count in an orthotopic xenograft mouse model. Additionally, in 50 clinical BCP-ALL samples, AHR and IDO were co-expressed in a disease-specific manner at mRNA and protein levels, while their mRNA levels showed a significant correlation with disease-free survival duration. These results indicated that PAH/IP exposure promotes BCP-ALL disease progression.

Preliminary investigation of polycyclic aromatic hydrocarbons (PAHs) concentration, compositional pattern, and ecological risk in crude oil-impacted soil from Niger delta, Nigeria

Crude oil contamination could serve as an important source of polycyclic aromatic hydrocarbons (PAHs) in the environment. Determining the concentration and distribution of PAHs and their ecological risk could provide clues for appropriate remediation. The present study investigated the concentrations, composition pattern, and ecological risk of PAHs in crude oil-contaminated soil collected from the Niger Delta, Nigeria. The concentrations of Σ₂₉PAHs and 16 priority US-EPA PAHs (Σ₁₆PAHs) in the soil ranged from 24230.68 to 40845.32 ng/g (average: 29953.47 ng/g) and 7361.66-14141.49 ng/g (average: 9819.96 ng/g), respectively. The concentrations of Σ₁₆PAHs US-EPA in all the studied locations far exceeded the safety value of 1000 ng/g set by the soil quality guidelines of Switzerland and above which is regarded as being highly contaminated for Agricultural soils of Poland. The percentage composition of 2-, 3-,4-, 5-, and 6-ring in the soils were 33.69%, 56.31%, 9.47%, 0.52%, and 0.02% of the total PAHs, respectively, indicating the predominance of low molecular weight PAHs typical of petrogenic origin. Ecological risk assessment indicated a high risk to the soil biota and ecosystem in the studied soil samples as presented by individual PAH and total PAHs. 2-, 3- and 4-ring PAHs in the soil contributed significantly to the ecological risk burden in the soils. This research work provides useful information on the ecological risk associated with crude oil contamination and consequently would assist the government in formulating precise, targeted, and effective remediation measures for soil contaminated with crude oil.

Human Health Assessment of Sixteen Priority Polycyclic Aromatic Hydrocarbons in Contaminated Soils of Northwestern Algeria

BACKGROUND

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental organic contaminants generated by incomplete combustion of organic materials that are widely distributed in soils.

OBJECTIVES

This study represents the first attempt to examine the health toxicity of 16 detected PAHs in contaminated soil, via different exposure pathways to populations in northwestern Algeria.

METHODS

The toxicity equivalency quotients (TEQ) of PAHs were evaluated. The carcinogenic risk assessment of incremental lifetime cancer risk (ILCR) from ingestion, inhalation, and dermal exposure pathways to each PAH in soil are described.

RESULTS

Incremental lifetime cancer risk values were in the upper limit of the tolerable range (10^-6-10^-4) for adults and children. The total cancer risk of PAH-contaminated soils for children, adolescents and adults was 2.48×10^-5, 2.04×10^-5 and 3.12×10^-5mg.kg^-1d^-1, respectively. The highest potential cancer risks were identified for adults and children, with adolescents having the lowest risks. Across exposure pathways, the dermal contact and ingestion pathways had the greatest contributions to the carcinogenic risk of human exposure to PAHs.

CONCLUSIONS

Further research and guidelines are needed for risk assessments of PAHs in agricultural, residential/urban, and industrial areas, and further risk assessments should include risks posed by exposure through air.

COMPETING INTERESTS

The authors declare no competing financial interests.