Toxicity assessment due to sub-chronic exposure to individual and mixtures of four toxic heavy metals

Effects of sub-chronic Cd exposure on levels of copper, selenium, zinc, iron and other essential metals in rat renal cortex

Cd (Cd) is a nephrotoxic environmental pollutant that causes generalized proximal tubule dysfunction. Even though the specific mechanisms by which Cd damages the kidney have yet to be fully elucidated, there is evidence to suggest that some of these nephrotoxic effects may result from the ability of Cd to alter the levels and function of metals such as Cu, Se, Zn and Fe within the kidney. In order to further explore this issue, we examined the effects of subchronic Cd exposure on tissue levels of a panel of metals (Ca, Cu, Fe, K, Mg, Na, Se and Zn) in the rat renal cortex. Adult male Sprague-Dawley rats were treated with CdCl₂ (0.6 mg Cd/kg body weight in isotonic saline by subcutaneous injection, 5 days per week for 6, 9 or 12 weeks). At each time point, 24 h urine samples were collected and assayed for levels of protein, creatinine, β₂ microglobulin and cystatin C. Samples of renal cortex were removed and assayed for levels of the metals of interest by inductively-coupled mass spectrometry at Michigan State University. Results showed that at 9 and 12 weeks, Cd caused significant increases in urine volume and urinary protein with no change in creatinine excretion. Increases in the excretion of the urinary biomarkers β₂ microglobulin and cystatin C were evident after 6 weeks of Cd exposure. Results of the metal analyses showed that Cd caused significant increases in tissue levels of Cu and Se at all of the time points examined. Tissue levels of Zn were transiently elevated at 6 weeks but declined to control levels at 9 and 12 weeks. Cd caused a significant decrease in levels of Fe at 9 and 12 weeks. Cd had no effects on any of the other metals. Tissue levels of Cd were 530 ± 52, 863 ± 23, 837 ± 23 ppm dry weight at 6, 9 and 12 weeks, respectively. These results indicate that the early stages of Cd nephrotoxicity are associated with alterations in renal tissue levels of Cu, Se, Zn and Fe. The fact that the changes in levels of the metals occurred during the early stages of Cd toxicity raises the possibility that the alterations in renal cortical metal content may play some role in the pathophysiology or Cd-induced injury.

Factors associated with self-reported health: implications for screening level community-based health and environmental studies

Background

Advocates for environmental justice, local, state, and national public health officials, exposure scientists, need broad-based health indices to identify vulnerable communities. Longitudinal studies show that perception of current health status predicts subsequent mortality, suggesting that self-reported health (SRH) may be useful in screening-level community assessments. This paper evaluates whether SRH is an appropriate surrogate indicator of health status by evaluating relationships between SRH and sociodemographic, lifestyle, and health care factors as well as serological indicators of nutrition, health risk, and environmental exposures.

Methods

Data were combined from the 2003–2006 National Health and Nutrition Examination Surveys for 1372 nonsmoking 20–50 year olds. Ordinal and binary logistic regression was used to estimate odds ratios and 95 % confidence intervals of reporting poorer health based on measures of nutrition, health condition, environmental contaminants, and sociodemographic, health care, and lifestyle factors.

Results

Poorer SRH was associated with several serological measures of nutrition, health condition, and biomarkers of toluene, cadmium, lead, and mercury exposure. Race/ethnicity, income, education, access to health care, food security, exercise, poor mental and physical health, prescription drug use, and multiple health outcome measures (e.g., diabetes, thyroid problems, asthma) were also associated with poorer SRH.

Conclusion

Based on the many significant associations between SRH and serological assays of health risk, sociodemographic measures, health care access and utilization, and lifestyle factors, SRH appears to be a useful health indicator with potential relevance for screening level community-based health and environmental studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-016-3321-5) contains supplementary material, which is available to authorized users.

A method for heavy metal exposure risk assessment to migratory herbivorous birds and identification of priority pollutants/areas in wetlands

Wetlands are important habitats for migratory birds but have been degraded by many anthropogenic factors including heavy metal contamination. Birds inhabiting wetlands are exposed to pollutants. In this study, a method for exposure risk assessment of migratory herbivorous birds and identification of priority pollutants/areas was developed and employed in East Dongting Lake wetland (EDT). Four heavy metals (Cr, Cu, Pb, and Cd) in sedge and soil samples from ten lesser white-fronted goose (Anser erythropus) habitats in EDT were investigated. Results showed that negative effect of Cr and Pb on lesser white-fronted goose may occur while the concentrations of Cu and Cd are considered to be relatively safe. Prioritize threats were decreased in the following sequence: Cr > Pb > Cu > Cd. Cr and Pb were considered to be the priority pollutants. Spatial interpolation based on geostatistical methods showed that Spring Breeze Lake should draw much attention. Furthermore, regions with high hazard index were identified to be priority areas of EDT for risk management.

Assessment of the Central Effects of Natural Uranium via Behavioural Performances and the Cerebrospinal Fluid Metabolome

Natural uranium (NU), a component of the earth's crust, is not only a heavy metal but also an alpha particle emitter, with chemical and radiological toxicity. Populations may therefore be chronically exposed to NU through drinking water and food. Since the central nervous system is known to be sensitive to pollutants during its development, we assessed the effects on the behaviour and the cerebrospinal fluid (CSF) metabolome of rats exposed for 9 months from birth to NU via lactation and drinking water (1.5, 10, or 40 mg·L(-1) for male rats and 40 mg·L(-1) for female rats). Medium-term memory decreased in comparison to controls in male rats exposed to 1.5, 10, or 40 mg·L(-1) NU. In male rats, spatial working memory and anxiety- and depressive-like behaviour were only altered by exposure to 40 mg·L(-1) NU and any significant effect was observed on locomotor activity. In female rats exposed to NU, only locomotor activity was significantly increased in comparison with controls. LC-MS metabolomics of CSF discriminated the fingerprints of the male and/or female NU-exposed and control groups. This study suggests that exposure to environmental doses of NU from development to adulthood can have an impact on rat brain function.

Potential Biotechnological Strategies for the Cleanup of Heavy Metals and Metalloids

Global mechanization, urbanization, and various natural processes have led to the increased release of toxic compounds into the biosphere. These hazardous toxic pollutants include a variety of organic and inorganic compounds, which pose a serious threat to the ecosystem. The contamination of soil and water are the major environmental concerns in the present scenario. This leads to a greater need for remediation of contaminated soils and water with suitable approaches and mechanisms. The conventional remediation of contaminated sites commonly involves the physical removal of contaminants, and their disposition. Physical remediation strategies are expensive, non-specific and often make the soil unsuitable for agriculture and other uses by disturbing the microenvironment. Owing to these concerns, there has been increased interest in eco-friendly and sustainable approaches such as bioremediation, phytoremediation and rhizoremediation for the cleanup of contaminated sites. This review lays particular emphasis on biotechnological approaches and strategies for heavy metal and metalloid containment removal from the environment, highlighting the advances and implications of bioremediation and phytoremediation as well as their utilization in cleaning-up toxic pollutants from contaminated environments.