Climate change in Sweden

The issue of climate change in Sweden has received significant public and political attention and the mitigation of its effects has been high on the agenda of the three latest Governments of Sweden, the former Cabinet of Göran Persson (1996−2006), the previous Cabinet of Fredrik Reinfeldt (2006–2014) and the current Löfven cabinet (2014–present). Sweden aims for an energy supply system with zero net atmospheric greenhouse gas emissions by 2050.[1]

Sweden's projected Köppen climate classification map for 2071-2100.

Climate history of Sweden

Temperature rise in Sweden's climate (1750–2013)

Since the beginning of the Quaternary time period approximately 2.5 million years(Before present), Sweden's climate has alternated between glacial periods and interglacial periods. The glacial periods lasted for up to 100,000 years with temperatures possibly 20 °C lower than today's. Colder temperatures resulted in ice sheets covering most or all of Sweden. The interglacial periods were shorter, lasting 10,000–15,000 years. During these periods the climate was similar to today's with extensive forests and ice-free summers. The latest of these glacial periods was the Weichselian glaciation, lasting from about 115,000 years BP until about 11,500 years BP. At its peak 20,000–17,000 years BP, it extended into the northern parts of Germany and Poland. The transition to the current interglacial period was marked by a retreat of the Ice sheets and gradually warmer temperatures. By 6,000–7,000 years BP, the temperature was slightly warmer than today and most of the southern half of the country was covered in deciduous forests. The temperature has fluctuated since then with a weak cooling trend, leading to a relative increase in coniferous tree-cover.


Emissions

In 2019 Sweden placed number four in the Climate Change Performance Index by Germanwatch with 76.28 points out of 100. No country was granted position one to three in the list as ”No country is doing enough to prevent dangerous climate change.”[2] Sweden has also been ranked first in both the 2014 and 2016 editions of the Global Green Economy Index (GGEI) where Sweden performs well overall and within the topic of climate change performance where it is one of the top developed countries due to the relatively low emissions intensity of the Swedish economy.[3]

The following table shows the yearly total emission of greenhouse gas in Sweden in million tonnes of carbon dioxide equivalent (Mt CO2). Values for EU28 and world to compare trends. [4]

Year Sweden (Mt CO2) EU28 (Mt CO2) World (Mt CO2)
1970 119 5 507 24 305
1980 104 6 214 29 989
1990 81 5 744 32 772
2000 81 5 297 35 962
2010 79 4 957 45 934
2015 67 4 500 49 113

The following table shows the yearly emission of greenhouse gas in Sweden in tonnes of carbon dioxide equivalent per capita (t CO2/capita). [4]

Year Sweden (t CO2/capita) EU28 (t CO2/capita) World (t CO2/capita)
1970 14.7 12.5 6.6
1980 12.5 13.4 6.7
1990 9.5 12.0 6.2
2000 9.1 10.9 5.9
2010 8.4 9.8 6.6
2015 6.9 8.9 6.7

For the total carbon dioxide emissions in 2009, without other Greenhouse gases or land use, at 50.56 million tonnes Sweden ranked in place 60 out of 216 countries, below Libya 55.0 million tonnes, Serbia 52.3 million tonnes and Finland 52.15 million tonnes. For the per capita carbon dioxide emissions in 2009, at 5.58 tonnes per capita (t/capita), Sweden ranked shared place 82 out of 216 countries having the same emissions as Ukraine. This was only slightly below the carbon dioxide emissions per capita in China 5.83 t/capita.[5]

In 2000, Sweden ranked in place 76 out of 185 countries for the per capita greenhouse gas emissions when taking any land use changes into account. Without considering land use changes the country ranked at fifty eighth.[6]

Climate gas emission in 2018 of public workers in Sweden was 410,000 tonnes (196,000 workers, ca 2 tonnes pro person). Naturvardsverket encourage to reduce the annual emissions in public sector.[7] In 2019 nine first months Karolinska institutet have reduced 5% all air travels and 18% Swedish air travels compared to year 2018.[8]

Road emissions

Share of biofuel increased from 22% to 23% in 2019. Road emissions declined by 2% from 2018 to 2019. To reach transport climate target by 2030 road traffic climate emissions must decline 8% a year (Sven Hunhammar, director in Trafikverket)[9]


Aviation emissions

According to Swedavia there was 40 million aviation travels in Sweden in 2019. Number decreased 9% in domestic flights and decreased 2% in international flights compared to 2018.[10] Swedish population in August 2019 was ca 10.3 million. This makes approximately in average 3.88 air travels per each citizen in Sweden in 2019.

Swedish aircraft greenhouse gas emissions equaled those of Swedish personal car traffic in 2017 according to the Swedish Environmental Protection Agency and a Chalmers University study published 31 May 2019.[11] Total emissions in 2017 was one tonne carbon dioxide equivalent per Swedish person. This is five times the global average.[12]

According to Swedish TV news, the Swedish government supports taxing aviation equal to private car traffic in 2019. Swedish TV news calculated that tax will make travel to Thailand 8,900 Swedish krona more expensive.[13]

Chalmers University report 2019

Global civil aviation accounts for 4–5% of total greenhouse gas emissions and these emissions are increasing. Greenhouse gas emissions from air travel are substantial for high-income countries like Sweden. Chalmers University Gothenburg developed methodology to calculate Swedish aviation emissions.[14][15]

The climate impact of aviation, is effected in addition to CO2 emissions by emissions of nitrogen oxides above 8000 meters and the warm aircraft emissions forming ice crystals. Total emission were estimated by calculating the CO2 emissions by 1.9 for international flights, and by 1.4 for domestic flights. Calculation excluded emissions from the production of fuel which is 10-20% in the EU.

The Swedish population’s air travel emission based on country of residence was 10 million tonnes CO2eq, in business 20% and in private travel 80%. The amount 10 million tonnes CO2eq can be compared with the bunker fuels metric which showed a total of 3.1 Mt CO2. Emissions were ca 1.1 tonnes CO2 equivalents per Swedish capita in 2017 compared to global average 0.2 tonnes per capita.

The Swedish aviation emissions are in total approximately equal to the emissions from the Swedish passenger vehicle traffic. Calculation exclude contribution of the tourists aviation visiting Sweden. Aviation emission was 170 g CO2 per passenger kilometre compared to 50 gram per kilometre and person in a car with three passengers.

Large emitters in Sweden

Listed below, an overview of large emitters of CO2 equivalents registered in Sweden in the European Union Emission Trading Scheme (EU ETS).[16] In 2018, the 584 entities registered in Sweden in EU ETS, emitting at least one tonne of CO2e, combined had verified emissions of 22,624,282 tonnes of CO2e. The column "Part of SE sum in EU ETS" is based on this sum, not the total emissions in Sweden.

Large emitters in Sweden.
Emitter Verified emissions (tonnes of CO2e)[16] Registered activity Year Part of SE sum in EU ETS Ownership comment
Scandinavian Airlines 2466820 Airline 2018 11% In early 2018 Danish state owned 14%, Swedish state 15%, Norwegian state 10%.[17] Parts of emissions likely related to activities outside Sweden.
Luleå KVV (CHP) 2120996 Combustion of fuels 2018 9% Owned to equal share by SSAB and Luleå Municipality.[18]
Slitefabriken 1740412 Production of cement clinker 2018 8% Owned by HeidelbergCement, through Cementa AB[19]
Preemraff Lysekil 1625082 Refining of mineral oil 2018 7% Owned by Preem
SSAB Oxelösund 1462246 Production of pig iron or steel 2018 6% Owned by SSAB. Swedish state owned 2.25% in 2016.[20]
SSAB Luleå 1058183 Production of pig iron or steel 2018 5% Owned by SSAB. Swedish state owned 2.25% in 2016.[20]
Krackeranläggningen, Borealis 636536 Combustion of fuels 2018 3% Owned by Borealis[21]
St1 Refinery AB 547101 Refining of mineral oil 2018 2.4% Owned by St1
Preemraff Göteborg 536000 Refining of mineral oil 2018 2.4% Owned by Preem
Värtan, Stockholm Exergi 499698 Combustion of fuels 2018 2.2% Owned to equal share by Stockholm Municipality and Fortum, a Finnish state-owned company.[22]
LKAB Kiruna 436371 Metal ore roasting or sintering 2018 1.9% Swedish state owned 100% in 2018.[23]

EU Renewable Targets

Sweden met its EU member-agreed binding renewable 2020 target in 2012.[24]

2014 United Nations Climate Change Conference

At the 2014 United Nations Climate Change Conference the Swedish Society for Nature Conservation (SSNC) demanded:[25]

  1. Swedish government should confirm the given election promises of 40% emission decline by 2020
  2. International 5-years goals
  3. Binding for every country
  4. SEK4 billion Kr Swedish green fund for 2015–2018
  5. Actively aim concrete agreement text already in Lima 2014

181 students took initiative to work in 2015 for two weeks to improve Swedish climate change carbon footprint in relation to green food, solar energy, bicycles, customs, consumption and wastes.[26]

Policy

Sweden has applied policy instruments and measures for climate change mitigation since the 1980s.[27] The instruments used include economic instruments (such as CO
2
tax, subsidies, penalties), legislation, voluntary agreements and a dialogue between the state and business enterprise. The main instruments are described below:

Carbon dioxide tax instrument

In Sweden, there are so far three different taxes levied on energy products (mainly fossil fuels), namely energy tax, sulphur tax and CO
2
tax. Energy taxation has been used as a policy instrument ever since the oil crisis of the 1970s to support renewable energy and nuclear power. Energy tax was reduced by half in 1991 during the tax reform, simultaneously with the introduction of a CO
2
tax on fossil fuels, with exceptions on ethanol, methanol, other biofuels, peat and wastes.

Renewable energy certificate system

As one part of the Government's long-term energy policy to reduce GHG emissions, the Swedish government introduced a voluntary international system for trading "green certificates", i.e. the renewable energy certificate system (RECS). With effect from 1 May 2003, RECS intends to encourage and increase the proportion of electricity produced from renewable energy sources. This will be done by payment of a levy in proportion to certain fraction of their electricity during the year. For example, during the first year (2003), users will be required to buy 7.4 per cent of the electricity generated from renewable sources

Renewable energy subsidies and continuous investment on R&D

Since 1991, Sweden started many programs to encourage the use of renewable energy and new technology development, e.g. Energy Policy program (Long and short term programs that focus on ways to increase the supply of renewable electricity, to reduce electricity consumption, and to promote energy efficiency), Green Certificate Scheme (Generators using solar, wind, biomass, geothermal, wave or small hydro are awarded one certificate for each MWh produced, and all consumers are obliged to buy enough certificates to cover a set proportion of their use).

International collaboration and carbon trading systems

Sweden also shows its leadership in international cooperation and competence on the climate change issues. Sweden actively took part in some international climate policy programs, such as Prototype Carbon Funds (PCF) and Activities Implemented Jointly (AIJ)

Public participation

Public participation is quite important in addressing climate change and its effects and developing adequate responses. Without the support of the public, it is impossible to implement a new policy instrument successfully. For example, one cannot anticipate that bio ethanol and bio diesel could be widely consumed without support and understanding from the general population. Therefore, information to raise the public's level of knowledge concerning the climate issue is necessary.

One public-private initiative, led by the KTH Royal Institute of Technology, is the Viable Cities program, which works with nine Swedish cities, including Stockholm, Gothenburg, and Malmö, to support becoming carbon neutral by 2030. Viable Cities' Chief Storyteller is tasked with increasing public participation by developing effective forms of climate communication that promote public engagement.[28][29]

2018 Climate Act

A Climate Act that targets zero net greenhouse gas emissions by 2045 has been in force since January 1, 2018.[30] After 2045 negative net emissions are targeted. The scope includes compensation projects abroad and emissions trading, but excludes aviation emissions.[31]

Plan 2019

The Swedish government published a new plan on 17 December 2019 with 132 actions. Climate law has been in place since 2017. Sweden's goal is to reduce greenhouse gases 85% from the 1990 level by 2045. The 2019 plan outlines specific targeted reductions for aviation and sea travel. The plan includes a carbon tax, tax reform that supports climate and environment goals, a green tax, a climate LCA for buildings in 2022, the requirement that all electricity, heating and transport must be carbon zero in 2045, and promotes private renewable energy projects to make them easier and cheaper. The short term goal is to reduce emissions from transport sector including aviation within Sweden at least 70% by 2030. Alternatives to private cars in cities are considered. A new price system for collective traffic will be introduced latest in 2022.[32] [33] [34]

Oil phase-out

The government created a Commission on Oil Independence (Kommissionen för att bryta oljeberoendet i Sverige till år 2020) and in 2006 it proposed the following targets for 2020:

  • Consumption of oil in road transport to be reduced by 40–50%
  • Consumption of oil in industry to be cut by 25–40%
  • Heating buildings with oil, a practice already cut by 70% since the 1973 oil crisis, should be phased out
  • Overall, energy should be used 20% more efficiently

Public perception of climate change

A 2002 survey showed that over 95% of respondents said that the use of tax money for addressing climate change was either "Very important" or "Fairly important". A little over half of the respondents were willing to change the use of hot water, electricity consumption and travel arrangement in order to reduce the impact of climate change. A little under half did not want to decrease internal building temperatures as a means of reducing climate change impact.[35] A201

Forestry

Forest owners and forestry professionals don't seem to be worried about climate change affecting forests in Sweden. For example, Forest owners in Kronoberg believe that climate change effects are distant and long-term. Stakeholders focus more on personal experience rather than results of how climate change will affect forests in the future. Another forest professional says that nothing they can do today can affect the changes that will happen in the future.[36]

Natural disasters prevention

Sweden has socioeconomical advantages that help higher the safety awareness to prevent natural disasters. The Swedish Civil Contingencies Agency (MSB) creates guidelines and strategies to help the society adapt to climate change.

Floods

As Sweden is affected every year by damaging floods, the MSB maintains and compiles general flood inundation maps, which are used for risk vulnerability analysis, emergency preparedness and in land use planning by municipalities. Flood prevention can include pumping equipment, embankments and dykes, or devices to shut down water supply and sewage systems.

Forest fires

The MSB has created a national information system for fire brigades. The system is found on the Internet and it provides information about how the climate can affect vegetation fire risks. It provides data that helps with prevention and can assist in decision-making.

Storms

The MSB provides generators that can be borrowed by areas that are hit by a storm and have lost power.

Landslides

Because of Sweden's location and the nature of the ground, landslides can affect some areas. The MSB provides general stability mapping for areas susceptible to landslides. The maps show which areas can be affected and which areas are in need of detailed geotechnical surveys.

Areas where consequences of a storm can be serious, the government grants 40 million Swedish kronor per year for preventions. Municipalities that have preventive measures can apply for subsidy from these allocated funds. A municipality that has been affected by a natural emergency has the right to ask the state for compensation to cover the exceeding costs.[37]

Storms

Winter storms Gudrun in 2005 and Per in 2007 in southern Sweden overthrew huge volumes of forest and caused power cuts.[38] Storm Per on 14 January 2007 affected 440,000 electricity users and Gudrun 620,000 customers. The reallocation of capital due to power disruptions during and after storm Per was estimated to be between SEK 1 800 and 3 400 million. The network operators cost was ca SEK 1 400 million, of which SEK 750 million compensation for affected customers. The costs for electricity consumers was estimated to SEK 180–1 800 million.[39]

Cyclone Gudrun in the North Sea 8 January 2005

Gudrun Storm

Gudrun storm hit Sweden on 8 January 2005. Before the wind speeds stopped, they had reached a maximum of 43 m/s. Wind speeds were at their strongest in the Bay of Hanö where they reached hurricane level of 33 m/s with gusts of 42 m/s. Areas like Skåne, Blekinge, Halland, Kronoberg, Gotland, and parts of Jönköping, Kalmar, and Västra Götaland counties were hit with winds reaching 30 m/s or more. Additionally, gusts of winds hit Södermanland coast, Lake Mälaren, Lake Hjälmaren and southern parts of Stockholm County. A total of eleven counties were strongly affected by the storm.

Estimates of about 730,000 users were without electricity the night of 8 January. The storm also damaged distribution networks of Vattenfall, Kreab Öst and other smaller companies. All the electricity damage also affected telephone and computer networks.

Despite the storm occurring in January, the weather at the time was mild which made the need for heat less than usual. District heating systems in urban areas did not suffer from long power cuts to cause problems. However, smaller areas did suffer from heating systems failures.

Millions of trees were torn by the roots and others were cut at the trunk. Trees blocked roads and seized traffic. The lack of frost in the ground caused spruce trees to be vulnerable to the high winds. 75 million cubic meters of forest was felled which is equal to several years of normal felling in the affected areas.

A major problem was telephone systems failure which delayed the clearing of roads and repair of overhead lines.

Nursing homes and elderly care services were also affected as individual safety alarms did not work. People were stranded in their cars on blocked roads. Seven people were killed in accidents and others were injured on the night of 8 January. Other deaths occurred after the storm, for example, one man was killed while attempting to fix his roof. In addition, people suffered from PTSDs.[37]

Future climate in Sweden

By the end of the century, Sweden's climate will be different from today's. There are uncertainties regarding the exact scope of the change one of which is the world's political trajectory regarding climate policy.[40]

Temperature

By the 2080s average temperatures are set to rise by 3–5 °C. The climate in the Mälardalen region will be similar to that of northern France. Winter temperatures are likely to see a greater increase than spring, summer and autumn temperatures. By the end of the century winters could be up to 7 °C warmer than today on average. The Norrland coast will probably be the region that sees the highest increases in temperature.[40] In May 2018 mean temperature was more than in average +5 °C in most Sweden and +2.5 °C in most Europe. In July 2018 mean temperature was more than in average +3-4 °C in most Sweden.[41] In July 2018 Italy, Norway, Poland and France sent help to fight the dozens of forest fires in Sweden.[42]

Precipitation

Sweden's future climate is expected to be wetter, with an increase in intense rain events. Most of the increase in precipitation will be during winter and a larger proportion will fall as rain. Summers will be drier and see a reduction in heavy rain events, particularly in the southern parts of Sweden.[40]

Wind

Climate models differ on whether Sweden's climate will get windier or not. Some models predict an increase in average wind speed, whilst others predict a decrease. The predictions of one climate model able to resolve wind gusts show an increase in the speed of wind gusts in the future.[40]

Baltic Sea

The surface temperature of the Baltic Sea will increase as the air temperature increases. Some models predict up to 4 °C increases in surface water temperature. Sea ice cover is expected to decrease and be localized to the northern Gulf of Bothnia by the end on the century. The salinity of the Baltic Sea is predicted to fall in some climate models as a result of increased influx of freshwater from the mainland, though other models differ significantly with some even showing an increase in salinity.[40]

Health Concerns

Climate change may affect the health status of the population in several ways.[43]

  • Warmer weather conditions can affect the elderly and vulnerable people in periods of extremely warm weather.
  • Spread of vector-borne diseases, in particular, tick-borne infections like Lyme disease (borreliosis) and tick-borne encephalitis. Ticks have spread northwards and can now even be found in the regions of Norrland. Also, there are still five species of mosquitoes in Sweden that may spread the malaria parasite. With the last indigenous case reported in the 1930s, a few new cases of malaria may appear with increasing temperature. The anopheles species of mosquitoes that spread the malaria parasite are sensitive to weather conditions that can be affected by climate change. Increased precipitation affects the number of hatching places of the mosquitoes, while an increase in humidity and temperature increases the life span of the mosquitoes and the development of the malaria parasite inside the mosquito.[44]
  • Quality of water and food can be affected by higher temperatures in the summer.
  • Air quality may be changed with a different composition of dust and pollen grains.[43] Studies of future scenarios project that the spreading of ragweed northwards may cause new cases of allergy and asthma.[45]

See also

References

  1. Renewables 2014 Global Status Report, page 29
  2. Burck, Jan; Hagen, Ursula; Marten, Franziska; Höhne, Niklas; Bals, Christoph. "The Climate Change Performance Index: Results 2019". Germanwatch, Bonn. Retrieved 2 December 2019.
  3. Tamanini, Jeremy; Dual Citizen LLC (September 2016). Global Green Economy Index 2016. Dual Citizen LLC.
  4. Crippa, M.; Oreggioni, G.; Guizzardi, D.; et al., eds. (2019). "Fossil CO2 and GHG emissions of all world countries - 2019 Report, EUR 29849 EN, Publications Office of the European Union, Luxembourg, 2019". Retrieved 18 November 2019.
  5. World carbon dioxide emissions data by country: China speeds ahead of the rest Guardian 31 January 2011
  6. "WRI Climate Analysis Indicators Tool (registration required to access data)".
  7. Koldioxidutsläpp från myndigheters tjänsteresor och transporter De sammanlagda utsläppen av koldioxid från Sveriges myndigheters tjänsteresor och transporter ökar igen och utsläpp från maskiner och övriga fordon står för den största ökningen. Även resorna med flyg har ökat Naturvardsverket 10.6.2019
  8. KI:s flygresor stor miljöbov – ändrade reseregler ska få ner utsläppen SVT 23.10.2019
  9. Minskade utsläpp från vägtrafiken 2019
  10. Flygresandet till och från Sveriges större flygplatser minskade med fyra procent under fjolåret jämfört med rekordåret 2018. Flygresandet till och från Sveriges större flygplatser minskade med fyra procent under fjolåret jämfört med rekordåret 2018. DI 10 januari 2020 + SVT
  11. Naturvårdsverkets nya beräkning: Flyget lika stor klimatbov som personbilar 31 maj 2019
  12. Växthusgasutsläpp från den svenska befolkningens flygresor
  13. 8 900 kronor i skatt på Thailandsresa Swedish TV News, 2 June 2019
  14. Measuring greenhouse gas emissions from international air travel of a country’s residents methodological development and application for Sweden Jörgen Larsson, Anneli Kamba, Jonas Nässéna and Jonas Åkermanb, Environmental Impact Assessment Review, 72: 137-144
  15. Climate footprint from Swedish residents’ air travel Anneli Kamb and Jörgen Larsson Chalmers Göteborg, February 2019
  16. "Verified emissions 2018". European Union emissions trading system (EU ETS). Retrieved 28 November 2019.
  17. "Norway to sell remaining SAS airline stake". The Local. Retrieved 1 December 2019.
  18. "Lulekraft" (in Swedish). Retrieved 1 December 2019.
  19. "Slitefabriken" (in Swedish). Retrieved 1 December 2019.
  20. "LKAB adds MSEK 113 to SSAB" (in Swedish). Retrieved 1 December 2019.
  21. "Borealis unit in Stenungsund" (in Swedish). Retrieved 1 December 2019.
  22. "Facts about Stockholm Exergi" (in Swedish). Retrieved 1 December 2019.
  23. "About LKAB". Retrieved 1 December 2019.
  24. Renewables 2014 Global Status Report, page 102
  25. Dags för Sverige att visa ledarskap för klimatet 1 December 2014
  26. Berghs hjälper Naturskyddsföreningen att klimatmaxa Dags för Sverige att visa ledarskap för klimatet The Swedish Society for Nature Conservation 4 December 2014
  27. "Sweden in the forefront for a green society".
  28. "Connecting the future to our cities". Viable Cities. 2019. Retrieved 28 December 2019.
  29. O'Sullivan, Feargus (11 November 2019). "To Survive Climate Change, We'll Need a Better Story". CityLab. Retrieved 28 December 2019.
  30. "As of today, Sweden has a new Climate Act!".
  31. "The climate policy framework".
  32. Lövin om nya klimatplanen: Ambitiös men når inte målen SVT 17 December 2019
  33. En samlad politik för klimatet Government 17 December 2019
  34. Klimatpolitiska handlingsplanen – Fakta-PM Government 17 December 2019
  35. Boman, Mattias; Leif Mattsson (2008). "A note on attitudes and knowledge concerning environmental issues in Sweden". Journal of Environmental Management. Elsevier. 86 (3): 575–579. doi:10.1016/j.jenvman.2006.12.041.
  36. "Learning about adaptation among forestry stakeholders" (PDF). Stockholm Environment Institute.
  37. https://energimyndigheten.a-w2m.se/ResourceComment.mvc?resourceId=2347
  38. "Stormen Per – två år efter Gudrun". Archived from the original on 29 January 2012. Retrieved 15 December 2011.
  39. Storm Per Archived 8 June 2012 at the Wayback Machine 2007
  40. "SOU 2007:60 Sweden facing climate change – threats and opportunities". www.government.se.
  41. Extremvärme allt vanligare i världen Swedish TV News 18 July 2018
  42. Flera skogsbränder i landet Swedish TV News 18 July 2018
  43. "Hälso- och sjukvården bör förbereda sig för ändrat klimat". www.lakartidningen.se (in Swedish). Retrieved 22 May 2017.
  44. Jaenson, Thomas GT (1985). Medicinsk entomologi. Liber. ISBN 91-40-05112-9.
  45. "Environmental Health Perspectives – Climate Change and Future Pollen Allergy in Europe". ehp.niehs.nih.gov. Retrieved 22 May 2017.
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