Antibiotic cocktails harmful to freshwater bacteria
New research has indicated that, at its current levels in the environment, a commonly used antibiotic (chlortetracycline) is toxic to freshwater bacteria. Moreover, when combined with four other antibiotics, the collective effect is greater than the sum of the individual effects.
Antibiotics are used extensively to treat bacterial infections in both human and veterinary medicine. However, the active substances in the drugs do not completely disappear when ingested but are excreted and passed into sewage systems. Even when the waste water has been treated, small amounts of antibiotics persist and are present in both groundwater and freshwater. Antibiotics are designed to target bacteria in humans and animals, but little is known about their effect on freshwater bacteria.
The study measured the toxicity of five well-known antibiotics (streptomycin, chlortetracycline, chloramphenicol, fusidic acid and rifampicin) to samples of freshwater bacteria extracted from a shallow lake in Sweden. These particular antibiotics all work by inhibiting the synthesis of proteins in bacteria and all of them affected the freshwater bacteria but with different levels of toxicity.
Chlortetracylcine was the most toxic antibiotic and streptomycin was the least toxic. Streptomycin required a concentration that was over 500 times greater (79.1 micromoles (µmol) per litre) than chlortetracycline (0.138 µmol per litre) to produce the same toxic effects that harmed 50 per cent of bacteria.
Researchers created curve diagrams to illustrate the relationship between antibiotic concentration and their toxic effects. On the whole, these curves were quite flat, i.e. toxicity did not increase by very much if concentration levels increased. This could be due to the differing sensitivities of individual bacterial species within the sample.
Guidelines, such as those produced by the European Chemicals Agency (ECHA), often suggest using relatively steep curves to predict toxic effects. According to the results of the study, this could underestimate the effects of low concentrations. For example, the ECHA guidelines suggest that the concentration/toxicity curve follows a gradient of 1:10, but if this was applied to the antibiotic rifampicin, then the point at which the ECHA curve predicts no more toxic effects, would actually still be toxic to a third of the bacteria.
The research also examined the toxic effects of a mixture of all five antibiotics in a set ratio. The results were compared with the effects predicted by two popular methods to estimate mixture toxicity: Concentration Addition (CA) and Independent Action (IA). CA assumes that the individual substances of a mixture behave as if they were dilutions of one another, whereas IA assumes that all substances in a mixture have effects that are independent of one another. There are arguments both for and against using either method.
When compared to the actual results, CA slightly underestimated the observed toxic effects of the mixture by a factor of 1.5, whereas IA slightly overestimated the toxicity by a factor of 0.3. This is contrary to usual patterns where CA tends to predict a higher toxicity than IA in most situations and suggests that the toxicity of this antibiotic mixture might be an exception, at least to freshwater bacteria. The choice of whether to use CA to estimate toxicity of antibiotic mixtures will depend on the risk in underestimating the mixture hazard.
Source: Brosche, S. & Backhaus, T. (2010) Toxicity of five protein synthesis inhibiting antibiotics and their mixture to limnic bacterial communities. Aquatic Toxicology. 99: 457-465.
Contact: [email protected]
Theme(s): Chemicals, Risk assessment
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New tool to analyse the greenness of products and processes
Researchers have created a new Green Option Matrix (GOM) to describe and compare the ever growing number of options to develop green products and processes. The GOM was used to analyse 142 companies belonging to the Dow Jones Sustainability World Index.
More and more companies are recognising the advantages of going green, whether it is to improve their legitimacy, their competitiveness or their ecological responsibility. This is reflected by the increasing number of companies obtaining the European Eco-label, which has grown from 50 in 2000 to more than 1000 in 2010. However, what is actually meant by ‘green’ is still debated. The study developed the Green Option Matrix to clarify the meaning of ?green? when used to describe the products and processes of companies.
The matrix uses three dimensions to describe the environmental contributions of a green product. Firstly it considers the environmental focus of the green product in terms of whether the focus is on materials, energy or pollution. Secondly it considers the stage in the product’s life cycle in which the environmental benefit occurs: before usage, during usage or after usage. Lastly it considers whether the environmental impact is less negative than conventional products, whether it is neither negative nor positive, or whether it positively contributes to the environment.
The matrix analysed 142 companies belonging to the Dow Jones Sustainability World Index (DJSWI) on the basis of information on their websites and in existing sustainability reports. The analysed companies belong to different sectors, as defined by the DJSWI: technology, consumer goods, industrial, and basic materials (which includes mining and forestry products).
This analysis highlighted popular practices, for example, almost all sectors have adopted practices such as size and weight reduction of products, packaging and materials. These practices have multiple benefits as they are related to all three types of environmental focus: they allow for material conservation, they reduce energy use and they reduce pollution from transportation.
Researchers analysed the diversity of options used by the different sectors. On the whole, the consumer goods sector was the most diverse in that the focus of their products and processes were distributed across materials, energy and pollution, across all stages of the life cycle and they had a range of positive impacts. This is probably because there are a wide range of products developed by the consumer goods sector, ranging from hybrid vehicles to energy-efficient household appliances, to intelligent energy use systems.
By providing a method to describe green products and processes in detail, the GOM can be used as a market analysis tool and a public relations tool. It can help companies analyse competitors? green practices and provide examples of how they can improve their own environmental impact. The GOM can also help companies communicate the environmental impacts of their products and practices, for example, it could be included in a company?s environmental/sustainability report, which would help prevent false claims of environmental credentials.
The researchers stress that the GOM is not intended to replace life cycle assessment tools, rather it intends to complement them by offering information that is more easily understood by consumers.
Source: Dangelico, R.M. & Pontrandolfo, P. (2010) From green product definitions and classifications to the Green Option Matrix. Journal of Cleaner Production. 18:1608-1628.
Contact: [email protected]
Theme(s):Environmental information services, Sustainable consumption and production
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Can discounting emission credits solve the CDM’s problems?
New research suggests that reducing the value of clean development mechanism (CDM) emission credits according to a country’s wealth and their emissions could encourage advanced developing nations, such as China and India, to leave the CDM, but would not necessarily accelerate CDM projects in the least developed nations.
The CDM allows industrialised countries to comply with their Kyoto Protocol emission reduction targets by investing in projects that reduce greenhouse gas (GHG) emissions in developing countries. One emission credit is granted for each tonne of CO2 equivalent emissions that are reduced and this credit can be used to offset the industrialised country?s own emissions.
However, critics have suggested that many reductions in emissions through the CDM are not additional reductions, and would have occurred without CDM investment in the projects. Also, one of the aims of the CDM is to encourage developing countries to address climate change, but most projects (71 per cent) are in so-called advanced developing countries, such as China, India and Brazil, who perhaps no longer need external support to develop their own projects. However, the Least Developed Countries (LDCs), who require the most support, host very few CDM projects.
A system of discounting emission credits has been suggested to decrease the value of credits generated by projects in certain countries, so as to encourage greater inflow of projects from LDCs. It could also incentivise advanced developing countries to wean themselves off CDM support.
The study investigated 108 CDM projects from 16 countries with specific focus on LDCs. It estimated the total costs of the projects, their potential to reduce GHG emissions and their competitiveness. Currently projects in advanced developing countries, particularly India and China, produce a much greater reduction in GHGs than LDCs for the same cost. For example, for the same cost (US$1 per tonne of CO2), projects in LDCs reduce emissions by an average of about 100 megatonnes, whilst Chinese projects reduce emissions by 4000 megatonnes.
Researchers analysed the impacts of two possible discounting schemes. The first reduced the value of emission credits on the basis of a country’s per capita GDP and their per capita emissions. This affected countries in the wealthiest Asian countries participating in the CDM, i.e. Qatar, UAE, Singapore, South Korea and Israel, whilst India and China were not affected.
This discounting scheme had the greatest impact on South Korea where the value of credits dropped by 56 per cent. However, despite discounting, projects in LDCs remained relatively uncompetitive, particularly compared to projects in China. This indicates that discounting is not a ‘magic bullet’ that instantly frees up potential for other countries. There are other barriers, such as availability of domestic capital and skilled workers.
The second discounting scheme was again based on reducing the value of credits according to a country’s per capita GDP and emissions. However, in this scheme discounting is immediately imposed when a country reaches half of the world’s average emissions and GDP. This would include China among the countries affected. Under this scheme, a larger proportion of projects in Qatar, UAE, Singapore, South Korea and Israel become uncompetitive.
However, most of China’s projects still remain relatively competitive and although LDC projects have smaller costs their number is still small. This indicates that discounting could incentivise some advanced developing countries to leave the CDM by reducing the financial reward and encourage them to engage in their own climate-related commitments, which may be more competitive due to the possibility to engage in emissions trading. For LDCs, financial and political barriers need to be removed before CDM can truly accelerate development in this area.
Source: Castro, P. & Michaelowa, A. (2010) The impact of discounting emission credits on the competitiveness of different CDM host countries. Ecological Economics. 70:34-42.
Contact: [email protected]
Theme(s): Climate change and energy, Sustainable development and policy analysis
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Call for Natural Capital to be mainstreamed into finance ministries
Although the value of biodiversity and ecosystem services has been recognised, it is still not fully integrated into policy-making. A new report has developed an action plan that recommends that governments create a ‘Natural Capital’ minister in the Finance Ministry, develop a set of Natural Capital Accounts and form an inter-departmental committee to oversee programmes in this area.
The Millennium Ecosystem Assessment (MA) and The Economics of Ecosystems and Biodiversity (TEEB) reports have demonstrated the significant impact of biodiversity loss and deteriorating ecosystems on our economies and societies. One of the reasons why these negative trends continue is that the value of ecosystems services, such as water treatment and purification services, as well as habitat for wildlife, provided by wetlands, is not recognised in the current macroeconomic system.
The report argues that if the value of ecosystem services, or ‘Natural Capital’, is included in the overall economic equation and decision making, governments will take better and more cost-effective decisions that respect the fundamental role that the environment plays in underpinning the economy and society’s wellbeing. Building on the knowledge of the MA and TEEB studies, it provides a clear set of political actions to ensure the value of ecosystems is integrated into policy making:
Valuing Natural Capital ? Environmental accounts incorporate the value of natural capital into the national accounting framework. This can be done by developing standardised methods for environmental accounting that would include data on areas such as natural resource assets, expenditure on environmental protection and damage costs caused by pollutants or costs of other degradation. This should be integrated into national accounts. Changes in natural capital should also be included in annual measures of national wealth in terms of the values of land, soil, timber and non-timber forest products.
Natural Capital within policy-making Natural capital must be mainstreamed into all policy areas, particularly into finance policy and macro-economic indicators, such as Gross Domestic Product (GDP). Environmental accounting must be embraced fully by policy makers. Attempts to create environmental accounts have failed in some countries because of a lack of buy-in at political level. Investing in natural capital also has benefits in terms of achieving other public policy goals, such as economic growth, job creation and energy and food security, and this should be better promoted in the political arena.
Governmental structure In order to ensure natural capital is taken into account by the political agenda, each country should have a minister responsible for natural capital within their Finance Ministry. This minister would oversee the latest environmental accounting methods and ensure the preparation of a set of Natural Capital Accounts. Alongside this a committee of ministers from each relevant department would ensure values of natural capital are integrated into policy across the board and produce a report to evaluate the implications of government policies on the environment and the economy. This committee could have an advisory group consisting of academic experts who would provide reports on the different components of natural capital, such as minerals, water resources, forests and marine fisheries.
National Audit Offices These could promote the integration of natural capital into policy making by considering natural capital in their audits of financial statements as well as by issuing public reports on economy, efficiency and effectiveness of government policies on natural capital.
Source: Stephens, C., Matthews, A., Johnson, I. et al. (2010) The GLOBE Natural Capital Action Plan (Draft version). Prepared by the GLOBE International Commission on Land Use Change and Ecosystems. Downloadable from www.globeinternational.info/wp-content/uploads/2010/10/Final.GLOBE-Natural-Capital-Action-Plan.pdf
Contact: [email protected]
Theme(s):Biodiversity, Environmental economics, Sustainable development and policy analysis
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Pest reduction in landscape containing GM maize
Populations of the European corn borer, a major pest of maize plants, fell significantly in areas where Bt maize (genetically modified maize) was planted alongside non-Bt maize, in a recent US study. This means that farmers who plant conventional maize crops could reap this benefit from farmers who plant Bt maize in the same landscape.
Maize that has been genetically modified by the insertion of proteins from the soil bacterium Bacillus thuringiensis is able to resist attack by the European corn borer, a moth that is a serious pest in particular in intensive maize cultivation, e.g.in a monoculture. The Bt proteins produced in the genetically modified maize are toxic to the moth larvae. In 2009, 63 per cent (22.2 million hectares) of the total maize area of the United States was planted with Bt maize. Maize is grown primarily in the states of Iowa, Illinois, Minnesota, Nebraska and Wisconsin and the European corn borer has been the most widespread maize pest in this region.
For this study, the researchers analysed records of the occurrence of adult moths and larvae in the five states from the 1960s to 2009. Bt maize has been grown commercially in the region since 1996.
Until the introduction of Bt maize crops, there is evidence of heavy outbreaks of European corn borers about every 6 to 8 years. However, surveys revealed that since the Bt crops were introduced these outbreaks are less severe and larval populations have dropped substantially.
Modelling suggests that before Bt maize was introduced commercially in Minnesota, there would have been 59 larvae for every 100 plants. After 1996, when 40 per cent of all the maize grown in Minnesota (on average) was Bt, the population fell to about 16 larvae for every 100 plants a decline of 73 per cent and this occurred in the non-Bt maize hectares. This suggests that the widespread adoption of Bt maize has significantly reduced numbers of the pest over a large area.
In addition, the researchers estimated that for the period 1996 to 2009, both Bt and non-Bt maize farmers in all five Midwestern states benefited financially through reduced losses in yields – by a total of nearly $6.9 billion. About 63 per cent of this figure, however, or $4.3 billion, accrued to farmers who grew non-Bt maize. Farmers who grew non-Bt maize benefited more than farmers who grew Bt maize because Bt maize growers had to pay a premium to purchase Bt seeds. Non-Bt growers therefore obtained the benefits of lower pest levels at no extra cost to themselves.
The European corn borer is known to attack over 200 different plants, including green beans, potatoes and many weeds in the Midwest USA. It is therefore likely that farmers growing crops other than maize will also benefit from lower populations of the pest. The researchers also note that the European corn borer causes significant yield losses in maize in Europe and suggest the potential for areawide suppression of the pest is likely to occur if Bt maize were widely adopted in Europe.
Integrated pest management strategies to control the European corn borer in maize, involving crop rotation, mechanical and biological control, should not be neglected since concerns have been raised that some pests could develop genetic mutations that allow them to become resistant to the Bt-toxins. Therefore, in the US, farmers are required to plant a percentage of non-Bt maize alongside Bt maize crops. This helps ensure there are still some non-resistant insects in the area that can breed with any resistant strains to prevent large numbers of resistant pests developing.
Source: Hutchison, W. D., Burkness, E. C., Mitchell, P. D. et al. (2010) Areawide Suppression of European Corn Borer with Bt Maize Reaps Savings to Non-Bt Maize Growers. Science. 330: 222-225.
Contact: [email protected]
Theme(s): Agriculture, Biotechnology
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New fossil fuel-free plastic made of wood
Scientists in the US have found a way to make a ‘biorenewable’ plastic from wood by-products. Their fossil fuel-free plastic is similar to polyethylene terephthalate (PET) – a material used to make plastic bottles and packaging. Such green chemistry approaches could help reduce reliance on dwindling fossil fuel resources.
As part of the European Union’s 2020 strategy for sustainable growth, it is committed to reducing the European community’s dependence on fossil fuels1. Besides investing in renewable energies, achieving this goal means developing new, greener ways to make widely-used materials from renewable resources. However, replacing synthetic plastics is challenging because some of their properties cannot be easily reproduced and many biorenewable alternatives prove not to be commercially viable.
The new plastic is made using an abundant wood polymer called lignin (wood is nearly a third lignin). The team combined vanillin a derivative of lignin with a fermentation product, acetic anhydride, to create the material. The final structure is similar to that of PET, one of the most widely used plastics worldwide. The only by-product of polymerisation is acetic acid, which can be recycled to make more acetic anhydride.
According to the researchers, their material not only mimics PET’s structure, it behaves similarly when heated and might even be easier to process. PET, normally brittle and glassy, becomes rubbery at around 70°C and melts at 265°C. The new material poly(dihydroferulic acid), or PHFA ? becomes rubbery at a similar temperature but melts a full 30°C lower, making it easier to process than PET itself. Many synthetic biorenewable polymers have lower glass transition and melting temperatures, which significantly limits their useful temperature range. Crucially, the new material’s thermal properties are sufficient to compete with those of many petroleum-based polymers.
These apparently favourable properties could make PHFA commercially viable as well as more environmentally-friendly than PET. The researchers are investigating other potential environmental impacts of PHFA, such as how it degrades. Preliminary research suggests that it breaks down into chemicals that resemble the building blocks of lignin, the natural product from which it is made.