Effects of local point source polychlorinated biphenyl (PCB) contamination on bone mineral density in deer mice (Peromyscus maniculatus)

Decrypting the skeletal toxicity of vertebrates caused by environmental pollutants from an evolutionary perspective: From fish to mammals

The rapid development of modern society has led to an increasing severity in the generation of new pollutants and the significant emission of old pollutants, exerting considerable pressure on the ecological environment and posing a serious threat to both biological survival and human health. The skeletal system, as a vital supportive structure and functional unit in organisms, is pivotal in maintaining body shape, safeguarding internal organs, storing minerals, and facilitating blood cell production. Although previous studies have uncovered the toxic effects of pollutants on vertebrate skeletal systems, there is a lack of comprehensive literature reviews in this field. Hence, this paper systematically summarizes the toxic effects and mechanisms of environmental pollutants on the skeletons of vertebrates based on the evolutionary context from fish to mammals. Our findings reveal that current research mainly focuses on fish and mammals, and the identified impact mechanisms mainly involve the regulation of bone signaling pathways, oxidative stress response, endocrine system disorders, and immune system dysfunction. This study aims to provide a comprehensive and systematic understanding of research on skeletal toxicity, while also promoting further research and development in related fields.

Toxicity of polychlorinated biphenyls in aquatic environments - A review

The assessment of polychlorinated biphenyls (PCBs) and their congeners resulting from the pollution of all environmental media is inherently related to its persistence and ubiquitous nature. In principle, determination of this class of contaminants are limited to the determination of their concentrations in the various environmental matrices. For solving many problems in this context, knowledge of the emission sources of PCBs, transport pathways, and sites of contamination and biomagnification is of great benefit to scientists and researchers, as well as many regulatory organizations. By far the largest amounts of PCBs, regardless of their discharged points, end up in the soil, sediment and finally in different aquatic environments. By reviewing relevant published materials, the source of origin of PCBs in the environment particularly from different pollution point sources, it is possible to obtain useful information on the nature of different materials that are sources of PCBs, or their concentrations and their toxicity or health effects and how they can be removed from contaminated media. This review focuses on the sources of PCBs in aquatic environments and critically reviews the toxicity of PCBs in aquatic animals and plants. The review also assesses the toxicity equivalency factors (TEFs) of PCBs providing valuable knowledge to other scientists and researchers that enables regulatory laws to be formulated based on selective determination of concentrations regarding their maximum permissible limits (MPLs) allowed. This review also supplies a pool of valuable information useful for designing decontamination technologies for PCBs in media like soil, sediment, and wastewaters.

Aroclor 1254 induced inhibitory effects on osteoblast differentiation in murine MC3T3-E1 cells through oxidative stress

This study aimed to evaluate the osteotoxicity of polychlorinated biphenyls in murine osteoblastic MC3T3-E1 cells, and to explore the underlying mechanism focused on oxidative stress. The cells were exposed to Aroclor 1254 at concentrations of 2.5-20 µmol/L, and then cell viability, oxidative stress, intracellular calcium concentration, osteocalcin content, and calcium nodules formation were measured. Aroclor 1254 reduced cell viability and induced overproduction of intracellular reactive oxygen species in a dose-dependent manner. Activity of superoxide dismutase was decreased, and malondialdehyde content was promoted after exposure. Moreover, inhibitory effects of Aroclor 1254 on calcium metabolism and mineralization of osteoblasts were observed, as indicated by reduction of the intracellular calcium concentration, osteocalcin content, and modules formation rate. The decreased expression of osteocalcin, alkaline phosphatase, bone sialoprotein, and transient receptor potential vanilloid 6 further confirmed the impairment of Aroclor 1254 on calcium homeostasis and osteoblast differentiation. Addition of the antioxidant N-acetyl-L-cysteine partially restored the inhibitory effects on calcium metabolism and mineralization. In general, Aroclor 1254 exposure reduces calcium homeostasis, osteoblast differentiation and bone formation, and oxidative stress plays a vital role in the underlying molecular mechanism of osteotoxicity.

Polychlorinated biphenyls (PCBs) in air and soil from a high-altitude pasture in the Italian Alps: evidence of CB-209 contamination

This study analyses the seasonal trend of polychlorinated biphenyls (PCB) concentrations in air and soil from a high-altitude mountain pasture in the Italian Alps. PCB concentrations in soil were generally comparable to background levels and were lower than those previously measured in the same area. Only CB-209 unexpectedly showed high concentrations with respect to the other congeners. GC-MS-MS identification was very clear, rising a new problem of increasing PCB contamination concerning only CB-209, which is not present in commercial mixtures used in the past in Italy and Europe. Considering all of the congeners, seasonal PCB trends were observed both in air and in soil that were related to the temperature and precipitation measured specifically in the study area. Highly significant relationships were found between the temperature-normalised concentrations in soil and the precipitation amounts. A north/south enrichment factor was present only in soil with rapid early summer re-volatilisation kinetics from soil to air and autumn re-deposition events from air to soil. Fugacity ratio calculations confirmed these trends. Surface soils respond rapidly to meteorological variables, while subsurface soils respond much more slowly. Seasonal trends were different for the northern and southern sides of the mountain. A detailed picture of the interactions among temperature, precipitation, mountain aspects and soil features was obtained.

Terrestrial ecosystem recovery following removal of a PCB point source at a former pole vault line radar station in Northern Labrador

Saglek Bay (LAB-2), located on the northeast coast of Labrador is a former Polevault station that was operated by the U.S. Air Force from 1953 to 1971 when it was abandoned. An environmental assessment carried out in 1996 determined that the site was contaminated with polychlorinated biphenyls (PCBs) with concentrations in soils far exceeding the Canadian Environmental Protection Agency (CEPA) regulation of 50 μg/g in three areas of the site (Beach, Site Summit, Antenna Hill). This led to remediation work carried out between 1999 and 2004 to remove and/or isolate all PCB-contaminated soil exceeding 50 μg/g and to further remediate parts of the site to <5 μg/g PCBs. In this study, spatial and temporal trends of PCB concentrations in soil, vegetation (Betula glandulosa and Salix spp.), and deer mice (Peromyscus maniculatus) were investigated over a period of fourteen (1997-2011) years in an effort to track ecosystem recovery following the removal of the PCB point sources. The data collected shows that PCB levels in vegetation samples are approximately four times lower in 2011 than pre-remediation in 1997. Similarly, PCB concentrations in deer mice in 2011 are approximately three times lower than those measured in 1997/98. Spatial trends in vegetation and deer mice continue to demonstrate that areas close to the former point sources of PCBs have higher PCB concentrations than those further away (and higher than background levels) and these residual PCB levels are not likely to decrease in the foreseeable future given the persistent nature of PCBs in general in the environment, and in particular in cold climates.

The effects of the organopollutant PCB 126 on bone density in juvenile diamondback terrapins (Malaclemys terrapin)

Bone is a dynamic tissue with diverse functions including growth, structural support, pH balance and reproduction. These functions may be compromised in the presence of organopollutants that can alter bone properties. We exposed juvenile diamondback terrapins (Malaclemys terrapin) to 3,3',4,4',5-pentachlorobiphenyl (PCB 126), a ubiquitous anthropogenic organochlorine, and measured organic content, apparent bone mineral density (aBMD) using radiography and computed tomography, and quantified bone microstructure using histological preparations of femora. PCB-exposed terrapins were smaller in total size. Skulls of exposed animals had a higher organic content and a skeletal phenotype more typical of younger animals. The femora of exposed individuals had significantly reduced aBMD and significantly more cortical area occupied by non-bone. Because bone is an integral component of physiology, the observed skeletal changes can have far-reaching impacts on feeding and locomotor performance, calcium reserves and ultimately life history traits and reproductive success. Additionally, we caution that measurements of bone morphology, density, and composition from field-collected animals need to account not only for relatedness and age, but also environmental pollutants.

1H NMR metabolomics of earthworm responses to polychlorinated biphenyl (PCB) exposure in soil

(1)H NMR-based metabolomics was used to examine the metabolic profile of D(2)O-buffer extracted tissues of Eisenia fetida earthworms exposed for 2 days to an artificial soil spiked with sub-lethal concentrations of polychlorinated biphenyls (PCBs) (0, 0.5, 1, 5, 10, or 25 mg/kg Aroclor 1254). Univariate statistical analysis of the identified metabolites revealed a significant increase in ATP concentration in earthworms exposed to the highest soil PCB concentration, but detected no significant changes in other metabolites. However, a multivariate approach which considers alterations in multiple metabolites simultaneously, identified a significant linear relationship between earthworm metabolic profiles and PCB concentration (cross-validated PLS-regression with 7 components, R(2)X = 0.99, R(2)Y = 0.77, Q(2)Y = 0.45, P < 0.001). Significant changes in pair-wise metabolic correlations were also detected as PCB concentration increased. For example, lysine and ATP concentrations showed no apparent correlation in control earthworms (r = 0.22, P = 0.54), but were positively correlated in earthworms from the 25 mg/kg treatment (r = 0.87, P = 0.001). Overall, the observed metabolic responses suggest that PCBs disrupted both carbohydrate (energy) metabolism and membrane (osmolytic) function in E. fetida. The ability of (1)H NMR-based metabolomics to detect these responses suggests that this method offers significant potential for direct assessment of sub-lethal PCB toxicity in soil.

Meteorological and pedological influence on the PCBs distribution in mountain soils

Polychlorinated biphenyls (PCBs) are a threat to environmental and human health due to their persistence and toxicological effects. In this paper, we analyse some meteorological and organic-matter-related effects on their distribution in the soils of an Alpine environment that is not subject to direct contamination. We collected samples and measured the contamination of 12 selected congeners from three soil layers (O, A1 and A2) and from North-, plain- and South-facing slopes on six different dates spanning the entire snowless portion of the year. We recorded the hourly air and soil temperatures, humidity and rainfall in the study period. We found evidence that PCBs contamination in soils varies significantly, depending on sampling date, layer and aspect. The observed seasonal trend shows an early summer peak and a rapid decrease during June. The layer effect demonstrates higher dry-weight-based concentrations in the O layer, whereas the differences are much smaller for SOM-based concentrations. Different factors caused significantly higher concentrations in northern soils, with a N/S enrichment factor ranging from 1.8 to 1.5 during the season. The southern site has significantly more rapid early-summer re-volatilisation kinetics (half-time of 16d for South, 25d for North).

Perinatal exposure to environmental contaminants detected in Canadian Arctic human populations changes bone geometry and biomechanical properties in rat offspring

Arctic inhabitants consume large proportions of fish and marine mammals, and are therefore continuously exposed to levels of environmental toxicants, which may produce adverse health effects. Fetuses and newborns are the most vulnerable groups. The aim of this study was to evaluate changes in bone geometry, mineral density, and biomechanical properties during development following perinatal exposure to a mixture of environmental contaminants corresponding to maternal blood levels in Canadian Arctic human populations. Sprague-Dawley rat dams were dosed with a Northern Contaminant Mixture (NCM) from gestational day 1 to postnatal day (PND) 23. NCM contains 27 contaminants comprising polychlorinated biphenyls, organochlorine pesticides, and methylmercury. Femurs were collected on PND 35, 77 and 350, and diaphysis was analyzed by peripheral quantitative computed tomography and three-point bending test, while femoral neck was assessed in an axial loading experiment. Dose-response modeling was performed to establish the benchmark dose (BMD) for the analyzed bone parameters. Exposure to the high dose of NMC resulted in short and thin femur with reduced mechanical strength in offspring at PND35. BMD of femur length, cortical area, and stiffness were 3.2, 1.6, and 0.8 mg/kg bw/d, respectively. At PND77 femur was still thin, but at PND350 no treatment-related bone differences were detected. This study provides new insights on environmental contaminants present in the maternal blood of Canadian Arctic populations, showing that perinatal exposure induces bone alterations in the young offspring. These findings could be significant from a health risk assessment point of view.