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Sodium hypochlorite is a chemical compound with the formula NaClO. [1] It is a clear, slightly yellowish solution with a characteristic odour. Sodium hypochlorite is unstable. Chlorine evaporates from the solution and when heated, the sodium hypochlorite disintegrates. This also happens when sodium hypochlorite comes in contact with acids, sunlight, certain metals and poisonous and corrosive gasses, including chlorine gas. It is a strong oxidator and reacts with flammable compounds and reductors. Sodium hypochlorite solution is a weak base that is inflammable.[2]
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On 19 April 2019, the Chinese Ministry of Ecology and Environment (MEE) issued a notice to seek public feedback on the General Program of Technical Guidelines for Environmental Health Risk Assessment, aiming to guide and regulate the environmental health risk assessment work and protect the public health. The consultation is set to end on 22 May this year. Environmental health risk assessment is an important foundation for environmental management. It can help governments to address the root cause of environmental hazards and proactively manage environmental pollutants with high health hazards, thus enabling great improvements to be made to ecological and environmental management. The General Program is positioned as a master plan guiding the institutional framework for environmental health risk assessment. Following the principle of ensuring “scientific, conservative, up-to-date, and traceable” practices, it applies to assessment of risks to human health from exposure to chemicals in the environment. According to the document, the procedure of environmental health risk assessment majorly contains six steps. The General Program provides detailed requirements for risk assessors in performing every one of the six phases in environmental health risk assessment. For example, in developing an assessment program, risk assessors should first identify several factors, including the objective, scope, category, content of assessment, methodology for collecting data, and quality control requirements. It should also be noted that some procedures and requirements are developed referring to relevant technical documents released by authorities of other countries as well as international organizations like the WHO. Further information is available at: MEE Notice
A research team in Ehime University characterised the complex composition of chlorinated, brominated and mixed halogenated dioxins as well as their major precursors in soils from e-waste burning and dismantling areas in Agbogbloshie (Accra, Ghana), a major hub of informal e-waste processing in Africa. The findings were published on February 22, 2019 in Environmental Science & Technology. E-waste, or Waste Electrical and Electronic Equipment (WEEE), refers to end-of-life products such as communication devices, consumer electronics and home appliances. E-waste contains substantial amounts of valuable metals to recycle, but is also considered as hazardous waste due to the presence of toxic substances such as heavy metals and many various plastic additives. A large volume of these hazardous waste materials has been recycled inappropriately, and treated informally in Asian and African developing countries using primitive methods such as circuit board heating and open burning of wires. These informal recycling activities have led to serious environmental pollution caused by the emission of not only contaminants contained in e-waste but also unintentionally formed secondary toxic chemicals. Dioxin-like compounds, or simply dioxins, are a group of unintentional contaminants generated during informal processing of e-waste with a wide range of potential toxic effects. However, assessment of the environmental and health impacts of dioxins from e-waste is challenging due to their complex composition. Chlorinated dioxins including polychlorinated dibenzo-p-dioxins and dibenzofurans are combustion by-products of polyvinyl chloride (PVC) used in wire coating. Lesser-known brominated dioxins are thermal degradation products of brominated flame retardants (BFRs), which are plastic additives designed to prevent accidental fires. Mixed brominated/chlorinated dioxins are also generated during e-waste burning, but have not been well characterised because of the difficulties in analysing their large number. The research team in Ehime University used special analytical methods based on two-dimensional gas chromatography (GC×GC) and time-of-flight mass spectrometry (ToFMS) to conduct a comprehensive profiling of halogenated contaminants in the soils collected near e-waste burning and dismantling areas. Polybrominated and mixed halogenated dibenzofurans (PBDFs and PXDFs) were the major dioxins detected. Their composition profiles suggest that PBDFs were generated from polybrominated diphenyl ethers (PBDEs), a group of flame retardants commonly found in e-waste plastics; and PXDFs mainly from PBDFs through successive bromine-to-clorine exchange. High concentrations of PXDFs in e-waste burning areas indicate that these “hidden” dioxins may contribute substantially to the total toxicity of the e-waste-derived dioxin mixture, and need to be included in future environmental and human exposure risk assessment.
