SEGH Articles

# Emerging Contaminants in the environment – is there a risk to health?

12 August 2012
In Europe and North America, there has been a gradual decrease in common environmental contaminants (heavy metals such as lead, cadmium; persistent organic pollutants such as DDT, Dioxin, PAH’s) in the environment. Common environmental contaminants, however, remain a public health concern in developing countries and newly industrialised countries.

In Europe and North America, there has been a gradual decrease in common environmental contaminants (heavy metals such as lead, cadmium; persistent organic pollutants such as DDT, Dioxin, PAH’s) in the environment. This improvement is largely due to a concerted effort of stricter regulations with improved monitoring, cleaner industrial processes and increased public awareness. Common environmental contaminants, however, remain a public health concern in developing countries and newly industrialised countries.

As we experience a decline in the levels and point sources of common chemicals, the focus has now been on the chemicals which were previously not considered as contaminants. They are not geogenic or air-born but are mainly synthetic by nature and produced to offer a range of societal benefits. Unlike common contaminants, ‘emerging chemical contaminants’ mostly find their way to the environment via diffuse sources i.e. domestic, commercial, and industrial uses. In addition, the development of more sensitive and new analytical capabilities that allows scientist to identify contaminants which are typically present in ultra-low concentrations (parts per billion to parts per trillion). The low concentrations combined with a lack of toxicological evidence make hazard characterisation technically challenging and thus the regulatory standards, where available, tend to be less rigorous and are advisory rather than prescriptive. In some cases (e.g. flame retardants) there are difficulties in identifying safer alternatives even when new evidence emerges about the health risk from the currently used materials.

Some examples of emerging contaminants include: perfluorocarbons ((e.g. perfluorooctane sulfonate (PFOS)), perfluorooctanoic acid (PFOA)), pesticides residues/metabolites (e.g. metaldehyde), pharmaceuticals and personal care products (e.g. steroids and antibiotics, fragrances, cosmetics), nanomaterials (e.g. buckeyballs or fullerenes; carbon nanotubes). These chemicals or their parent products are being manufactured to improve the quality and safety or to increase the efficiency in industrial processes. By nature, they are intended to last long or be resistant to microbial degradation in the environment. For example, PFCs contains only carbon and fluorine bonded together in strong carbon­-fluorine bonds which made them chemically inert and thermally stable. When these chemicals (e.g. PFOS, antibiotics, steroids) are released to the public sewer system, conventional water treatment processes can do little to render them harmless and go unabated to enter the wider environment and biotic food chain as a pollutant.

Our knowledge to relate the presence of emerging chemicals in the environment with public health significance is still at its infancy. Bioassays with animal models indicate the potential for toxicity to humans if exposed to a very high doses but such high dose exposure is unrealistic when compared to typical environmental concentrations. Uncertainty, however, remains over the potential health impacts from a low level chronic exposure due to their persistence and bioaccumulative nature. Studies with ecological receptors e.g. with fish in streams contaminated by steroids have shown evidence of hormone disruption. There is also concern that elevated exposure to antibiotics in water could lead to disease-resistant strains of bacteria, reducing the effectiveness of the current class of drugs. For the human population, the limited data available suggests that there is a need for more “prospective cohort” type study to characterise the association between environmental exposure to these substances, appropriate biomarkers and measurable health outcomes.

Emerging chemicals should be a source of concern to ecological and public health in all parts of the world. In this era of financial constraint and interdependent/connected economies, there is a need for shared research programme and data-sharing to enhance analytical capacity to determine their environmental occurrence, fate and transport.  There is also a need for improved risk assessment tools to characterise the exposure and extrapolation of ecological risk to public health if relevant and appropriate. Regulatory policy should encompass emerging chemicals in their monitoring regime, and encourage safer alternatives, increased awareness and risk reduction programme. Societies like the SEGH can facilitate research consortia or a task force drawing from its international expertise to influence the relevant public policy and apply for research funding. Further information on emerging chemicals can be found in websites of various regulatory and public health organisations such as European Chemicals Agency, US EPA, ATSDR.

Sohel Saikat, Health Protection Agency, UK.

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## Science in theNews

Latest on-line papers from the SEGH journal: Environmental Geochemistry and Health

• Fertilizer usage and cadmium in soils, crops and food 2018-06-23

### Abstract

Phosphate fertilizers were first implicated by Schroeder and Balassa (Science 140(3568):819–820, 1963) for increasing the Cd concentration in cultivated soils and crops. This suggestion has become a part of the accepted paradigm on soil toxicity. Consequently, stringent fertilizer control programs to monitor Cd have been launched. Attempts to link Cd toxicity and fertilizers to chronic diseases, sometimes with good evidence, but mostly on less certain data are frequent. A re-assessment of this “accepted” paradigm is timely, given the larger body of data available today. The data show that both the input and output of Cd per hectare from fertilizers are negligibly small compared to the total amount of Cd/hectare usually present in the soil itself. Calculations based on current agricultural practices are used to show that it will take centuries to double the ambient soil Cd level, even after neglecting leaching and other removal effects. The concern of long-term agriculture should be the depletion of available phosphate fertilizers, rather than the negligible contamination of the soil by trace metals from fertilizer inputs. This conclusion is confirmed by showing that the claimed correlations between fertilizer input and Cd accumulation in crops are not robust. Alternative scenarios that explain the data are presented. Thus, soil acidulation on fertilizer loading and the effect of Mg, Zn and F ions contained in fertilizers are considered using recent $$\hbox {Cd}^{2+}$$ , $$\hbox {Mg}^{2+}$$ and $$\hbox {F}^-$$ ion-association theories. The protective role of ions like Zn, Se, Fe is emphasized, and the question of Cd toxicity in the presence of other ions is considered. These help to clarify difficulties in the standard point of view. This analysis does not modify the accepted views on Cd contamination by airborne delivery, smoking, and industrial activity, or algal blooms caused by phosphates.

• Effects of conversion of mangroves into gei wai ponds on accumulation, speciation and risk of heavy metals in intertidal sediments 2018-06-23

### Abstract

Mangroves are often converted into gei wai ponds for aquaculture, but how such conversion affects the accumulation and behavior of heavy metals in sediments is not clear. The present study aims to quantify the concentration and speciation of heavy metals in sediments in different habitats, including gei wai pond, mangrove marsh dominated by Avicennia marina and bare mudflat, in a mangrove nature reserve in South China. The results showed that gei wai pond acidified the sediment and reduced its electronic conductivity and total organic carbon (TOC) when compared to A. marina marsh and mudflat. The concentrations of Cd, Cu, Zn and Pb at all sediment depths in gei wai pond were lower than the other habitats, indicating gei wai pond reduced the fertility and the ability to retain heavy metals in sediment. Gei wai pond sediment also had a lower heavy metal pollution problem according to multiple evaluation methods, including potential ecological risk coefficient, potential ecological risk index, geo-accumulation index, mean PEL quotients, pollution load index, mean ERM quotients and total toxic unit. Heavy metal speciation analysis showed that gei wai pond increased the transfer of the immobilized fraction of Cd and Cr to the mobilized one. According to the acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) analysis, the conversion of mangroves into gei wai pond reduced values of ([SEM] − [AVS])/f oc , and the role of TOC in alleviating heavy metal toxicity in sediment. This study demonstrated the conversion of mangrove marsh into gei wai pond not only reduced the ecological purification capacity on heavy metal contamination, but also enhanced the transfer of heavy metals from gei wai pond sediment to nearby habitats.

• Cytotoxicity induced by the mixture components of nickel and poly aromatic hydrocarbons 2018-06-22

### Abstract

Although particulate matter (PM) is composed of various chemicals, investigations regarding the toxicity that results from mixing the substances in PM are insufficient. In this study, the effects of low levels of three PAHs (benz[a]anthracene, benzo[a]pyrene, and dibenz[a,h]anthracene) on Ni toxicity were investigated to assess the combined effect of Ni–PAHs on the environment. We compared the difference in cell mortality and total glutathione (tGSH) reduction between single Ni and Ni–PAHs co-exposure using A549 (human alveolar carcinoma). In addition, we measured the change in Ni solubility in chloroform that was triggered by PAHs to confirm the existence of cation–π interactions between Ni and PAHs. In the single Ni exposure, the dose–response curve of cell mortality and tGSH reduction were very similar, indicating that cell death was mediated by the oxidative stress. However, 10 μM PAHs induced a depleted tGSH reduction compared to single Ni without a change in cell mortality. The solubility of Ni in chloroform was greatly enhanced by the addition of benz[a]anthracene, which demonstrates the cation–π interactions between Ni and PAHs. Ni–PAH complexes can change the toxicity mechanisms of Ni from oxidative stress to others due to the reduction of Ni2+ bioavailability and the accumulation of Ni–PAH complexes on cell membranes. The abundant PAHs contained in PM have strong potential to interact with metals, which can affect the toxicity of the metal. Therefore, the mixture toxicity and interactions between diverse metals and PAHs in PM should be investigated in the future.