13 March 2020 Bulletin

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Arsenic

Sodium bicarbonate, aka baking soda or bicarbonate of soda, is a soluble odourless whiteArsenic is a chemical element with the symbol As, an atomic mass of 74.921 595, and an atomic number of 33. It is in the pnictogens group of the periodic table and its element category is Metalloid. Arsenic has a metallic grey appearance and is primarily used in alloys of lead. Its multiple allotropes come in a variety of colours—including yellow and black—but only the grey form is important to industry. Arsenic is found in many minerals, usually in combination with metals sulfur, but it can also present as a pure elemental crystal. Arsenic is both an organic and inorganic chemical. It is a Group-A carcinogen and all forms of the element are a serious risk to human health. [1, 2]

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ECHA starts work on making drinking water safer

ECHA will start to compile a list of substances that can be safely used in materials that come into contact with drinking water. The aim is to improve consumer protection and ensure equal safety standards for industry. Helsinki, 14 January 2020 – With the recast of the Drinking Water Directive, ECHA has been given a task to compile and manage an EU positive list of chemicals that can be safely used in materials that come into contact with drinking water. The first positive list is expected to cover around 1500 chemicals and will be adopted by the European Commission by 2024. As the first EU positive list will be based on the existing lists in the Member States, a review programme will be introduced through which the Agency will reassess all substances on the list within 15 years from its publication. ECHA will prioritise substances for the systematic review and recommend expiry dates for them. Each approved substance will be authorised for use for a limited period of time. The timing of the reviews will be based on the hazardous properties of the substances as well as the quality of and how up to date underlying risk assessments are. Companies will need to submit a review application to ECHA if they want to keep their substances on the positive list. Companies will also need to submit an application if they want to add new substances to the list. Member States can also submit dossiers to ECHA to remove substances from the list or to update entries – for example, when a concentration limit for a substance in drinking water changes. ECHA will assess applications and dossiers and its Committee for Risk Assessment will form its opinion for further decision making by the Commission. Bjorn Hansen, ECHA’s Executive Director says: “We will assess substances used in materials to produce, for example, water pipes and taps, and look forward to working to help improving the quality of drinking water throughout Europe. Hereby, we can rely on our expertise in risk assessment, achieve efficiencies and ensure consistency across different pieces of chemicals legislation. Harmonising the assessment also ensures a level playing field for companies providing these materials across different European countries.” ECHA will support the Commission in developing information requirements for applicants and assessment methods. This work will be done in close collaboration with the European Food Safety Authority (EFSA) due to the close links with food contact materials. Background The provisional agreement on the recast of the Drinking Water Directive was reached on 18 December 2019 and is still subject to formal approval by the European Parliament and the Council. Following approval, the Directive will be published in the EU's Official Journal and enter into force 20 days later.

From ‘living’ cement to medicine-delivering biofilms, biologists remake the material world

The bricks in Wil Srubar’s lab at the University of Colorado, Boulder, aren’t just alive, they’re reproducing. They are churned out by bacteria that convert sand, nutrients, and other feedstocks into a form of biocement, much the way corals synthesize reefs. Split one brick, and in a matter of hours you will have two. Engineered living materials (ELM) are designed to blur boundaries. They use cells, mostly microbes, to build inert structural materials such as hardened cement or woodlike replacements for everything from construction materials to furniture. Some, like Srubar’s bricks, even incorporate living cells into the final mix. The result is materials with striking new capabilities, as the innovations on view last week at the Living Materials 2020 conference in Saarbrüken, Germany, showed: airport runways that build themselves and living bandages that grow within the body. “Cells are amazing fabrication plants,” says Neel Joshi, an ELM expert at Northeastern University. “We’re trying to use them to construct things we want.” Humanity has long harvested chemicals from microbes, such as alcohol and medicines. But ELM researchers are enlisting microbes to build things. Take bricks, normally made from clay, sand, lime, and water, which are mixed, molded, and fired to over 1000°C. That takes lots of energy and generates hundreds of millions of tons of carbon emissions annually. A Raleigh, North Carolina, company called bioMASON was among the first to explore using bacteria instead of heat, relying on the microbes to convert nutrients into calcium carbonate, which hardens sand into a sturdy construction material at room temperature. Now, several groups are taking the idea further. “Could you grow a temporary runway somewhere by seeding bacteria in sand and gelatin?” asks Sarah Glaven, a microbiologist and ELM expert at the U.S. Naval Research Laboratory. In June 2019, researchers at Wright-Patterson Air Force Base in Ohio did just that to create a 232-square-meter runway prototype. The hope, says Blake Bextine, who runs an ELM program for the U.S. Defense Advanced Research Projects Agency, is that rather than ferrying tons of materials to set up expeditionary air fields, military engineers could use local sand, gravel, and water, and apply a few drums of cementmaking bacteria to create new runways in days. The bricks and runway cement don’t retain living cells in the final structure. But Srubar’s team is taking that next step. In their self-reproducing bricks, researchers mix a nutrient-based gel with sand and inoculate it with bacteria that form calcium carbonate. They then control the temperature and humidity to keep the bacteria viable. The researchers could split their original brick in half, add extra sand, hydrogel, and nutrients, and watch as bacteria grew two full-size bricks in 6 hours. After three generations, they wound up with eight bricks, they reported in the 15 January issue of Matter. (Once the bacteria are done growing new bricks, the team can turn off the temperature and humidity controls.) Srubar calls it “exponential material manufacturing.” ELM makers are also harnessing microbes to make biomaterials for use in the human body. Microbes naturally exude proteins that bind to one another to form a physical scaffold. More bacteria can adhere to it, forming communal microbial mats known as biofilms, found on surfaces from teeth to ship hulls. Joshi’s team is developing biofilms that could protect the gut lining, which erodes in people with inflammatory bowel disease, creating painful ulcers. In the 6 December 2019 issue of Nature Communications, they reported that an engineered Escherichia coli in the guts of mice produced proteins that formed a protective matrix, which shielded the tissue from chemicals that normally induce ulcers. If the approach works in people, physicians could inoculate patients with an engineered form of a microbe that normally makes its home in the gut. In another medical use, bacteria could turn conventional materials into drug factories. In the 2 December 2019 issue of Nature Chemical Biology, for example, Christopher Voigt of the Massachusetts Institute of Technology and his colleagues describe seeding a plastic with bacterial spores that continuously generate bacteria. The microbes synthesize an antibacterial compound effective against Staphylococcus aureus, a dangerous infectious bacterium. A team of researchers led by Chao Zhong of ShanghaiTech University engineered biofilms for a different purpose: detoxifying the environment. They started with the bacterium Bacillus subtilis, which secretes a matrix-forming protein called TasA. Other researchers had shown that TasA was easy to genetically engineer to bind to other proteins. The team tweaked TasA to get it to bind an enzyme that degrades a toxic industrial compound called mono (2-hydroxyethyl terephthalic acid), or MHET. They then showed that biofilms created by the engineered bacterium could break down MHET—and that biofilms made by a mix of two engineered strains of B. subtilis could carry out a two-step degradation of an organophosphate pesticide called paraoxon. The results, which the team reported in the January 2019 issue of Nature Chemical Biology, raise the prospect of living walls that purify the air. Regulatory issues could slow progress, however. Many of the bacteria that ELM researchers have harnessed occur in nature and should not trigger regulatory scrutiny. But genetically engineered organisms will—and the prospect of engineered microbes embedded in, say, living walls might unsettle regulators. Still, Voigt predicts, “I think in 10 years, we’re going to find living cells in a whole range of living products.”

https://www.sciencemag.org

Digging up the dirt: are your home-grown vegies safe to eat?

The level of heavy-metal contamination in Australian gardens is being exposed by a Macquarie University program which is testing thousands of soil samples sent in by concerned citizens. Growing your own vegetables is supposed to be healthy but how much do you know about the soil they’re growing in? There could be metal contaminants in it and they could be getting into your crop. Fortunately, there’s an easy way to find out if your soil is OK using the VegeSafe program, a citizen science endeavour being run by Environmental Science staff at Macquarie University in partnership with Olympus, who manufactured a portable soil analysis device. Soil can pick up metal particles from many sources and these particles can remain for many years, says Professor Mark P Taylor, who is the Director of Macquarie University’s Energy and Environmental Contaminants Research Centre. "Your garden soil could still contain lead deposited back before leaded petrol was banned in 2002, from previous land use or residue from old-style lead paints. The allowable limit of lead in house paint was reduced to 0.01 per cent in 1991, down from a staggering 50 per cent before 1965," Taylor said. "Lead is not a nutritious trace element in your carrots: it’s a neurotoxin. Brain damage from lead exposure is irreversible. "Other metals, such as arsenic, cadmium, chromium, copper, manganese, nickel and zinc won’t do you any good either if there are high concentrations in your soil. They might not be harmful for adults but children are more vulnerable. Toxic doses are lower for smaller bodies and children are more likely to stick their dirty fingers in their mouth." High-tech tests VegeSafe is a citizen science program, probably the largest of its kind in the world, and is supported by public donations, of both funding and soil samples. Members of the public can send samples of their garden soil for analysis – and more than 3000 people have so far sent upwards of 15,000 soil samples. The VegeSafe team performs high-tech testing of these samples and provides the senders with a short report, as well as advice on things they can do to reduce the hazard if their soil is contaminated. The work has attracted worldwide interest and Taylor’s group has now combined with researchers in the US to produce an interactive mapping tool of residential environmental contamination. The program is also starting in New Zealand in early 2020. VegeSafe was recently named as Olympus Analytical Instrumentation’s Research Partner of the year, in recognition of the scientific and social value of the work it performs using X-ray fluorescence technology. If you are worried about the risk of metal contamination, you should arrange to get the soil tested before buying or renting a home, and before building a vegetable garden or chicken run. You can also organise testing for house paint dating from before 1997, ceiling dust from before 2002 and all rainwater tanks. If the results are unfavourable, there are a range of things you can do to minimise potential harm. You can find out more from VegeSafe.

https://www.lighthouse.mq.edu.au