Over the course of the previous three feature articles on Emerging Risks in Agriculture, we considered the latest information on respiratory, cardiac and mental health conditions and disorders; the impact of workplace exposure to biological chemical and physical agents; and the effect of environmental and demographic factors on worker health.
In this, our final instalment of the series, we provide an overview of the research into occupational conditions onset by hydraulic fracturing, or ‘fracking’, and also highlight advances in technology which may help to enhance workplace safety.
During 2017, A HSE report on information communication technology identified an ageing workforce, skills deficits and labour shortages as challenges facing farming, and further reported that technological solutions are emerging to deal with these challenges[i].
Most new research into work with robots focuses on safety and accidents, rather than health and diseases.
In September of 2017, NIOSH created the Centre for Occupational Robotics Research (CORR). The objectives of the project are to evaluate the potential benefits and risks of robots in the workplace, conduct workplace interventions to prevent robot-related worker injuries, and develop guidance for safe interactions between humans and robots[ii]. In October of 2017, three NIOSH researchers presented information about the application of robotics in the workplace, at the National Robot Safety Conference (USA)[iii].
NIOSH have also considered whether wearable exoskeletons will reduce or create hazards[iv]. These devices, ranging from whole-body suits to gloves, can reduce some of the mechanical stresses attributed to manual labour. However, potential risks associated with the exoskeleton include:
- Increased pressure on the chest;
- Increased load on the spine due to the weight of the device;
- Pressure wounds or compressed nerves due to poor fit of the device; and
- Spread of contagious diseases if many people use the same device and hygiene is poor.
Nevertheless, potential uses of robotics in agriculture include[v]:
- Static milking robots;
- Mobile dairy farm robots;
- Autosteer tractors (more than 300,000 tractors equipped with autosteer or tractor guidance were sold in 2016);
- Autonomous tractors;
- Unmanned spraying drones;
- Autonomous data mapping drones;
- Robotic implements for de-weeding;
- Autonomous de-weeding mobile robots;
- Robotic fresh fruit harvesting (such as a machine that picks oranges[vi]);
- Robotic strawberry harvesting; and
- Manned and unmanned robotic lettuce/vegetable thinning/harvesting.
Figure: Use of robotics in agriculture includes drones[vii]
It was reported, earlier in 2017, that researchers in Shropshire were able to sow and harvest a field of barley using only robots[viii].
Estimates, produced by the International Federation of Robotics, show that, by 2018, global sales of industrial robots will grow by 15% each year, with 70% of sales recorded in China, Japan, USA, South Korea and Germany[ix].
In edition 224 of BC Disease News (here), we discussed that 3D printers had emitted potentially hazardous ultrafine particles and volatile organic compounds. Working more than 40 hours each week with 3D printers was significantly associated with diagnoses of asthma or allergic rhinitis.
Last year, the European Agency for Safety and Health at Work published an expert review that provided a brief introduction to 3D printing and examined its risks[x]. Occupational health and safety challenges related to 3D printing include:
- Gas and material exposures;
- Material handling;
- Static electricity;
- Moving parts; and
The European Agency report noted that most materials used in 3D printing are known, and so are their effects on health. It provided an overview of the uses of 3D printing. Not more than 1% of the population owns a 3D printer. The majority of 3D printed products are manufactured at home and distributed within the sharing economy. Industrial 3D printing occurs less than home production. As an example, the economic contribution of the entire 3D printing industry in the Netherlands in 2015 was estimated at around €45 million, making up 0.005% of the country’s total gross national product. However, 3D printing is currently being encouraged as a way for farmers to develop and repair their own tools, in an effort to save expense.[xi] In January of 2017, it was reported that rural workers in Myanmar, have been using 3D printing as a means to design new sprinkler systems and water pumps.[xii]
Another application of 3D printing is the bioprinting of organic and/or living tissue, whereby organic matter can be built up by printing thin layers of cells. There have been numerous successful experiments of printing ‘living’ materials containing fungus or algae. However, this technique poses risks to health and hygiene and raises ethical issues. Last year, the Brazilian organisation, Embrapa Genetic Resources and Biotechnology's Laboratory of Nanobiotechnology (LNANO), has recently had an application approved to use bioprinting in agricultural research.[xiii]
Overall, the European Agency report concluded that the everyday impact of the 3D printer on physical safety in the workplace is likely to be limited.
However, a recent NIOSH study, comparing the printer emissions from the most commonly used type of desktop 3D printer and two models of black and white laser printers[xiv], found that certain chemicals, known as volatile organic compounds, were significantly lower with laser printers compared to 3D printers. The 3D printers also emitted 14 chemicals that laser printers did not emit. In addition, 3D printer emissions likely combined to form other chemicals. Even after printing, 3D printed objects emitted styrene, indicating that exposure beyond the actual process of printing may be a concern in the work place.
Figure: 3D printing[xv]
Increasingly, farmers are turning to renewable energy sources as a means to generate as much electricity as possible and provide a long-term source of income.[xvi] We now look at the risks associated with growing sources of energy.
Many farm machines are driven by fossil fuels. Although there was no mention of a ban affecting tractors, the Government recently announced that the sale of diesel and petrol cars would be banned from 2040 onwards.[xvii] Biofuels are being developed as alternatives to petrol and diesel fuels with the objective of reducing carbon emissions from liquid fuels. Biofuels, however, are not without their health-related drawbacks.
Figure: Biofuel pumps in the United States[xviii]
EFSA consider transmissible spongiform encephalopathy (TSE) to be the most relevant hazard caused by animal fat-based biofuels[xix]. Forms of TSE include bovine spongiform encephalopathy (BSE), in cattle, and variant Creutzfeldt-Jakob disease (vCJD), in humans. With the exception of BSE in cattle, which can cause vCJD in humans, there is no scientific evidence that other TSE’s can be transmitted to humans[xx]. TSE diseases can affect the brain and nervous system, and are fatal.
Animal fat also contains other biologically hazardous molecules, such as heat-resistant bacterial spores and viruses. TSE-causing agents have high resistance to destruction and are known to be stable at high temperatures.
A report, commissioned by the Department of Transport and the Department of Energy and Climate Change (now the Department for Business, Energy and Industrial Strategy) to provide advice on the UK strategy for development of biofuels, was published in July of 2017[xxi]. The report contained a small section on air quality and human health-related issues, which stated:
- Air quality studies show that emissions of some pollutants may be higher for biofuels when compared to fossil fuels, largely resulting from the emissions associated with feedstock production and biofuel processing (i.e. emissions from producing biofuels may be more significant than emissions from burning fossil fuels). For example, burning straw in sugar cane fields in Brazil causes substantial respiratory diseases, such as asthma and pneumonia, in sugar cane workers and local populations;
- Vehicular exhaust emissions of bioethanol blends vary with blend strength. In general, lower bioethanol blends have lower carbon monoxide (CO) and particulate matter (PM) emissions compared to petrol. Higher ethanol blends lead to comparable or slightly lower levels of CO, PM and oxides of nitrogen, but five to ten times higher emissions of acetaldehyde.
- It has been argued that, despite having lower PM emissions, biodiesel exhaust emissions could be potentially more harmful to human health because of higher proportions of ultra-fine particles. Smaller particles remain suspended in the air for longer, are more easily inhaled and are able to penetrate more deeply into the lungs.
- Other assessments on potential human health implications of biodiesel suggest that using biofuels compared to diesel fuels results in minimal health impacts.
- Routes of health effects in humans other than air pollution, such as water/soil pollution and occupational hazards are scarcely discussed in the literature, and should be explored further.
Macro-algae, or seaweed, is increasingly gaining attention as a potential feedstock for third generation biofuels[xxii], which may be commercially available by the year 2030. At present, however, greenhouse gas emissions are higher than those from fossil fuels, meaning that they are not a feasible option.
Use of solar panels in the UK has increased significantly in the last 5 years. On 25 March 2017, it was found that solar power had produced six times more electricity than the country’s coal-fired power stations on that day[xxiii]. However, the amount of solar forecast to be installed by 2022 is a fifth of the amount installed over the last five years[xxiv].
Figure: Solar panels[xxv]
In November of 2017, researchers at the Fraunhofer Institute for Solar Energy Systems published a press release on an experiment, involving 720 bi-facial solar panels situated over a third of a hectare of agricultural land. The solar panels were mounted on top of crops, near Lake Constance, with enough room to permit the operation of farm machinery beneath the panels. After a year of trials, the research showed that the dual-use system (agrophotovoltaics) increased the total productivity of the land by 60%.[xxvi]
Previously, in a document from 2010, the State Smart Transportation Initiative outlined the health risks associated with each stage of the solar panel life cycle[xxvii].
Risks Associated with the Installation and Use of Solar Panels:
- Because solar panels are encased in heavy-duty glass or plastic, there is little risk that small amounts of semiconductor material can be released into the environment.
- In the event of a fire, it is theoretically possible for hazardous fumes to be released and inhalation of these fumes could pose a risk to human health. However, researchers do not generally believe these risks to be substantial given the short-duration of fires and the relatively high melting point of the materials present in the solar modules.
- A greater potential risk associated with photovoltaic systems is the potential for shock or electrocution if an emergency responder comes in contact with a high voltage conductor.
- The strength of electromagnetic fields produced by photovoltaic systems do not approach levels considered harmful to human health established by the International Commission on Non-Ionizing Radiation Protection. Moreover the small electromagnetic fields produced by photovoltaic systems rapidly diminish with distance and would be indistinguishable from normal background levels within several yards.
Risks Associated with End-of-Life Management and Recycling of Solar Panels:
- If not properly decommissioned, the greatest end of life health risk from crystalline solar modules arises from lead containing solders. Under the right conditions it is possible for the lead to leach into landfill soils and eventually into water bodies.
Further, an article, published in April of 2017, identified the toxic chemicals emitted by solar panels and outlined the potential health effects upon exposure. Chemical agents found in solar panels include:
- Cadmium telluride,
- Copper indium selenide,
- Cadmium gallium (di)selenide,
- Copper indium gallium (di)selenide,
- Polyvinyl fluoride, and
- Crystalline silicon[xxviii].
It was noted that these materials pose a toxicity risk to lungs. In the case of cadmium telluride, the journal of Progress in Photovaltaics reported that exposure by inhalation caused lung inflammation and lung fibrosis. At moderate to high doses, death was observed. Similar observations were made in a Toxicology and Applied Pharmacology article, involving copper indium selenide, although death was not a feature of exposure. Elsewhere, in the Journal of Occupational Health, research into cadmium indium gallium (di)selenide, injected into the trachea, resulted in excessive fluid spots in the lungs, progressively worsening with time. Moreover, silicon tetrachloride has been found to kill plants and animals.
Hydraulic fracturing, or fracking, involves injecting a high-pressure mixture of water, sand and other chemicals into wells, in order to induce fissures in rocks that allow the release of gases. These gases are collected and used to provide power. In both the UK and USA, fracking has been promoted as a way to reduce dependence on foreign energy sources. Drilling companies suggest that trillions of cubic feet of shale gas may be recoverable from underneath parts of the UK[xxix].
Figure: Activities the hydraulic fracturing in process[xxx]
However, in early 2017, NIOSH, identified hydraulic fracturing as an occupational health and safety area needing attention. In America, hydraulically fractured wells provided two-thirds of the USA’s natural gas in 2015.[xxxi]
In December of 2017, UK media outlets reported that, ‘domestic fracking will finally begin in earnest in 2018’.[xxxii] Public support for fracking in the UK is low, primarily due to environmental and health concerns[xxxiii]. In addition, scientists have questioned whether the geology of the UK is actually suitable for fracking[xxxiv]. At this stage, the amount of hydraulic fracturing that will occur in the UK in the future is uncertain.
The link between hydraulic fracturing and farming is that much of the targeted areas for drilling of shale gas is rural farmland. As such, the hazardous risks associated with fracking are likely to affect the health and safety of agricultural workers.
In 2012, NIOSH evaluated that the transportation of hundreds of thousands of pounds of sand, during operations, generated dust that includes respirable crystalline silica, the inhalation of which can cause silicosis and lung cancer. [xxxv] [xxxvi]
Figure: Areas licensed for hydraulic fracturing in the UK (Source: BBC, 2015)[xxxvii]
EFFECTS OF FRACKING ON FARMING
In July of last year, it was reported that farmers had protested outside a fracking site in Lancashire[xxxviii].
Health concerns expressed by farmers about fracking include[xxxix]:
- Health and safety impacts on families and children nearby sites;
- Sickness and reproductive defects in livestock;
- Water, land and air contamination of crops;
- Frack fluid spillages and animal deaths;
- Hazardous exposure to vegetable crops, meat, eggs and dairy products entering the food chain;
- Chemical spills; and
- Water shortages.
Farmers are also concerned that fracking could reduce the value of their land, and that supermarkets may stop sourcing produce grown on drilling sites[xl].
Families and Children
In edition 215 of BC Disease News (here), we reported on an American study, published in 2017, into 1.1 million births in Pennsylvania between 2004 and 2013. It showed that there were greater risks of ill-health among infants born to mothers living within 2 miles of a hydraulic fracturing, or ‘fracking’, site.
There was evidence in support of negative health effects in babies born within 3km of fracking sites and the largest health impacts were seen among those living within 1km of a fracking site.
Among mothers living within 1km of a site, there was a 25% increase in the probability of low birth weight, and significant declines in average birth weight and in the infant health index.
Low birth weight is a risk factor for numerous negative outcomes, including infant mortality, attention deficit hyperactivity disorder, asthma, lower test scores, lower schooling attainment, lower earnings and higher rates of social welfare program participation.
The finding of a 25% increase in the probability of low birth weight, within 1 km of a fracturing site, is not inconsistent with findings from other studies that have investigated the effects of air pollution on foetal health.
Childhood cancer incidence has also been observed in Pennsylvania counties, though the standard incidence ratio of child leukemia was unremarkable.[xli]
Irrespective of this observation, a recent review of the chemicals used in hydraulic fracturing and their potential to cause childhood blood cancers found that, of 1177 chemicals, more than 80% had not been evaluated by the IARC. Of the 111 potential water contaminants and 29 potential air pollutants, (119 compounds), 49 water and 20 air pollutants were known, probable, or possible human carcinogens. A total of 17 water and 11 air pollutants (20 compounds) had evidence of increased risk of leukaemia/lymphoma[xlii].
In another 2017 study, volatile organic benzene compounds were found close to fracking operations[xliii]. Researchers monitored the urinary levels of a metabolite of benzene in pregnant women living near a Canadian fracking site. Results showed that these women were approximately 3.5 higher than those in the general Canadian population[xliv]. Levels were particularly high in indigenous women, though the differences were not statistically significant. The effects of benzene on developmental health have been widely studied, and include reduced birth weight, increased risk of childhood leukaemia, and birth defects such as cleft palate and spina bifida. The lead researcher of the study, Marc-André Verner, said:
‘Although the levels of muconic acid found in the participants’ urine cannot prove beyond reasonable doubt that they were exposed to high levels of benzene, these results do clearly demonstrate the importance of exploring human exposure to environmental contaminants in natural-gas (fracking) regions’.[xlv]
The researchers concluded that more extensive research is required, and they will undertake further studies in the future.
After opening more than 30 gas and oil wells in close proximity to her farm, North Dakota cattle farmer, Jacki Schilke, claimed that 5 of her cows had ‘dropped dead’, while she claimed to have suffered chronic lung pain, back pain, and rashes, over the course of the year. Ms Schilke attributed these events to fracking. Subsequent air testing confirmed the existence of higher than normal levels of chemical compounds in her vicinity, such as benzene, butane and chloroform.[xlvi]
Shale Gas Syndrome
Numerous online articles have reported on a case series study on health hazards caused by fracking.[xlvii] The study was limited, in that it was not epidemiological and did not compare exposed and unexposed workers.
However, the authors found adverse effects of fracking, including respiratory, reproductive, and growth-related problems in animals, and a spectrum of symptoms in humans, which they termed ‘shale gas syndrome’.
Symptoms of so-called ‘shale gas syndrome’, include a combination of burning eyes, sore throat, headaches, nosebleeds, vomiting, diarrhoea, and skin rashes. It has been reported that whenever fracking victims are compensated for their losses, they often are forced to sign non-disclosure agreements[xlviii].
As there is no systematic testing of air, soil or water for chemical contaminants, and there is no systematic health monitoring of nearby residents, researchers do not know which chemicals are present in the fracking process and therefore do not know which type of health effects testing should be conducted[xlix]. Ideally, comparisons between pre-fracking and post-fracking exposure could establish a route of human exposure, and confirm that health effects are caused by the claimed chemical exposure.
According to the American Public Health Association (APHA), in a 2012 report, it stated that evidence regarding health impacts of gas drilling is difficult to obtain, and that many uncertainties remain about the types of exposures and resulting health impacts[l].
In the USA, fracking companies are allowed to protect the precise identity and contents of fracking fluid under ‘proprietary’ or ‘trade secret’ designations. From a public health perspective, this makes exposure monitoring difficult, and makes it difficult for health agencies to offer advice to operators. However, a national hydraulic fracturing chemical registry, known as FracFocus, which was created in response to concerns about effects on health and the environment, provides public access to list of chemicals used in individual wells. As of December 2012, the registry contained more than 33,000 voluntary disclosures[li].
According to the House of Representatives’ Committee on Energy and Commerce, between 2005 and 2009, the 14 oil and gas service companies in the USA used more than 2,500 hydraulic fracturing products containing 750 chemicals and other components. The products ranged from unexpected items such as instant coffee and walnut hulls, to products known to cause adverse health effects, such as benzene, silica, lead, ethylene glycol and methanol[lii]. There is also the potential for exposure to diesel fumes, due to the use of diesel vehicles on site. Though the occupational safety issues are well understood and regulated, the occupational health issues are less well understood.
Figure: Hydraulic fracturing site in the Marcellus shale deposit, in the Northeastern USA[liii]
The emerging epidemiological studies, such as those outlined above, convey concerning adverse birth outcomes.[liv] There are few studies, at this time, which have focused on either worker or resident populations, exposed to fracking. Consequently, there is a need for more research to be conducted on potentially affected populations, as fracking operator activity, over recent months, indicates that UK fracking operations may begin imminently. Fracking is widespread throughout the USA, and has increased considerably in recent years, so studies from the USA should continue to offer insight into the risks faced by workers and residents in the UK. Hopefully, more comprehensive research can be used to initiate preventative measures for curbing occupational health risks, especially those affecting the agriculture industry.
[i] Foresight Report 2016 Digital revolution and the changing face of work. Health and Safety Executive. http://www.hse.gov.uk/horizons/assets/documents/foresight-report-2016.pdf http://www.hse.gov.uk/horizons/assets/documents/foresight-report-2016.pdf (Accessed 22 January 2018)
[ii] ROBOTICS. NIOSH. https://www.cdc.gov/niosh/topics/robotics/default.html (Accessed 9 January 2018)
[iii] NIOSH Presents: An Occupational Safety and Health Perspective on Robotics Applications in the Workplace. NIOSH Science Blog. 5 December 2017 https://blogs.cdc.gov/niosh-science-blog/2017/12/05/robot_safety_conf/ (Accessed 9 January 2018)
[iv] Exoskeletons in Construction: Will they reduce or create hazards? NIOSH Science Blog. 15 June 2017 https://blogs.cdc.gov/niosh-science-blog/2017/06/15/exoskeletons-in-construction/ (Accessed 9 January 2018)
[v] Agricultural Robots and Drones 2017-2017: Technologies, Markets, Players. IDTechEx. https://www.idtechex.com/research/reports/agricultural-robots-and-drones-2017-2027-technologies-markets-players-000525.asp (Accessed 12 January 2018)
[vi] Robotic citrus harvesting system by Energid. Energid. http://www.energid.com/experience/citrus-harvesting/ (Accessed 10 January 2018)
[vii] Image from https://pixabay.com/en/spraying-sugar-cane-sugar-cane-2746350/
[viii] Shropshire farm completes harvest with nothing but robots. 7 September 2017 https://www.engadget.com/2017/09/07/farm-robot-harvest-hands-free-hectare/ (Accessed 12 January 2018)
[ix] Foresight Report 2016 Digital revolution and the changing face of work. Health and Safety Executive. http://www.hse.gov.uk/horizons/assets/documents/foresight-report-2016.pdf http://www.hse.gov.uk/horizons/assets/documents/foresight-report-2016.pdf (Accessed 22 January 2018)
[x] 3D printing and additive manufacturing – the implications for OSH. European Agency for Safety and Health at Work. 6 July 2017 https://osha.europa.eu/en/tools-and-publications/publications/3d-printing-new-industrial-revolution/view (Accessed 12 January 2018)
[xiv] Stefaniak, A. B. et al. Characterization of chemical contaminants generated by a desktop fused deposition modeling 3-dimensional Printer. Journal of Occupational and Environmental Hygiene 14, 540–550 (2017). http://oeh.tandfonline.com/doi/full/10.1080/15459624.2017.1302589?src=recsys#.WlrNs6Nh2ex (Accessed 12 January 2018)
[xv] Image from http://maxpixel.freegreatpicture.com/Printer-Making-3d-printing-3d-Pressure-1455165
[xviii] By Mariordo Mario Roberto Duran Ortiz (Own work) [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons https://commons.wikimedia.org/wiki/File%3ABiofuel_pumps_DCA_07_2010_9834.JPG
[xix] EFSA Panel on Biological Hazards (BIOHAZ) et al. Evaluation of the Application for new alternative biodiesel production process for rendered fat of Cat 1 (BDI-RepCat process, AT). EFSA Journal 15, n/a-n/a (2017). http://onlinelibrary.wiley.com/doi/10.2903/j.efsa.2017.5053/full (Accessed 12 January 2018)
[xx] Transmissible Spongiform Encephalopathies (TSEs). EFSA. https://www.efsa.europa.eu/en/topics/topic/transmissible-spongiform-encephalopathies-tses (Accessed 12 January 2018)
[xxi] Sustainability of liquid biofuels. Royal Academy of Engineering. July 2017 https://www.raeng.org.uk/publications/reports/biofuels (Accessed 12 January 2018)
[xxii] Gegg, P. & Wells, V. UK Macro-Algae Biofuels: A Strategic Management Review and Future Research Agenda. Journal of Marine Science and Engineering 5, 32 (2017). http://www.mdpi.com/2077-1312/5/3/32/htm (Accessed 12 January 2018)
[xxiii] UK breaks solar energy record on sunny March weekend. The Guardian. 28 March 2017 https://www.theguardian.com/environment/2017/mar/28/uk-solar-energy-march-electricity (Accessed 12 January 2018)
[xxiv] Time to shine: Solar power is fastest-growing source of new energy. The Guardian. 4 October 2017 https://www.theguardian.com/environment/2017/oct/04/solar-power-renewables-international-energy-agency (Accessed 12 January 2018)
[xxv] By Pujanak (Own work) [Public domain], via Wikimedia Commons https://commons.wikimedia.org/wiki/File%3ASolar_panels_on_a_roof.jpg
[xxvii] Health and Safety Concerns of Photovoltaic Solar Panels. https://www.ssti.us/wp/wp-content/uploads/2016/09/Health_and_Safety_Concerns_of_Photovoltaic_Solar_Panels_2010_OR.pdf (Accessed 12 January 2018)
[xxviii] Toxic Chemicals in Solar Panels. 25 April 2017 https://sciencing.com/toxic-chemicals-solar-panels-18393.html (Accessed 12 January 2018)
[xxx] By US Environmental Protection Agency [Public domain], via Wikimedia Commons https://commons.wikimedia.org/wiki/File%3AHydraulic_Fracturing-Related_Activities.jpg
[xxxi] Hydraulically fractured wells provide two-thirds of U.S. natural gas production. United States Energy Information Administration. 5 May, 2016. https://www.eia.gov/todayinenergy/detail.php?id=26112 (Accessed 27 November 2017)
[xxxii] UK fracking to begin in earnest in 2018 after tough year for industry. The Guardian, 25 December 2018. https://www.theguardian.com/environment/2017/dec/25/fracking-start-2018-shale-gas-uk-industry-protests (Accessed 23 January 2018)
[xxxiii] Public support for fracking in the UK at record low, official survey reveals. The Guardian. 3 August 2017 https://www.theguardian.com/environment/2017/aug/03/public-support-for-fracking-in-the-uk-at-record-low-official-survey-reveals (Accessed: 25th November 2017)
[xxxiv] Scientists question UK geology’s suitability for hydraulic fracturing. JWN Energy. 22 August 2017. http://www.jwnenergy.com/article/2017/8/scientists-question-uk-geologys-suitability-hydraulic-fracturing/ (Accessed 27th November 2017)
[xxxv] Worker Exposure to Crystalline Silica During Hydraulic Fracturing. NIOSH Science Blog. 23 May 2012. https://blogs.cdc.gov/niosh-science-blog/2012/05/23/silica-fracking/ (Accessed 27th November 2017)
[xxxvi] Esswein, E. J., Breitenstein, M., Snawder, J., Kiefer, M. & Sieber, W. K. Occupational Exposures to Respirable Crystalline Silica During Hydraulic Fracturing. Journal of Occupational and Environmental Hygiene 10, 347–356 (2013).
[xxxvii] Image from http://www.bbc.com/news/uk-14432401
[xxxviii] Farmers at odds over fracking operation in Lancashire. Farmers Weekly 22 July 2017 http://www.fwi.co.uk/news/farmers-at-odds-over-fracking-in-lancashire.htm (Accessed 22 January 2018)
[xxxix] Fracking poses risk to UK farm animals and food safety, experts warn. The Ecologist, 17 September 2013. https://theecologist.org/2013/sep/17/fracking-poses-risk-uk-farm-animals-and-food-safety-experts-warn (Accessed 22 January 2018)
[xl] Frack & ruin: UK farmers fear financial devastation from shale drilling. https://www.rt.com/uk/193548-farmers-fracking-financial-ruin/ (Accessed 22 January 2018)
[xli] Fryzek, J., Pastula, S., Jiang, X. & Garabrant, D. H. Childhood Cancer Incidence in Pennsylvania Counties in Relation to Living in Counties With Hydraulic Fracturing Sites. Journal of Occupational and Environmental Medicine 55, 796 (2013). http://journals.lww.com/joem/Abstract/2013/07000/Childhood_Cancer_Incidence_in_Pennsylvania.12.aspx (Accessed 27 November 2017)
[xlii] Elliott, E. G. et al. Unconventional oil and gas development and risk of childhood leukemia: Assessing the evidence. Science of The Total Environment 576, 138–147 (2017). http://www.sciencedirect.com/science/article/pii/S0048969716322392 (Accessed 22 January 2018)
[xliii] Gilman, J. B., Lerner, B. M., Kuster, W. C. & de Gouw, J. A. Source Signature of Volatile Organic Compounds from Oil and Natural Gas Operations in Northeastern Colorado. Environ. Sci. Technol. 47, 1297–1305 (2013). http://pubs.acs.org/doi/abs/10.1021/es304119a (Accessed 27th November 2017)
[xliv] Caron-Beaudoin, É. et al. Gestational exposure to volatile organic compounds (VOCs) in Northeastern British Columbia, Canada: A pilot study. Environment International 110, 131–138 (2018). https://www.sciencedirect.com/science/article/pii/S0160412017310309 (Accessed 27th November 2017)
[xlv] Exposure to benzene during pregnancy: a pilot study raises concerns in British Columbia. Science Daily, 13 November 2017. https://www.sciencedaily.com/releases/2017/11/171113095435.htm (Accessed 20 November 2017)
[xlvii] Baamberger, M. & Oswald, R. E. Impacts of Gas Drilling on Human and Animal Health. New Solut 22, 51–77 (2012). http://www.aqlpa.com/sites/ass-010-aqlpa/files/files/gaz%20de%20schiste/Bamberger_Oswald_NS22_in_press.pdf (Accessed 22 January 2018)
[xlviii] The real cost of fracking: How America’s shale gas boom is threatening our families, pets and food.
[li] Goldstein, B. D. et al. The Role of Toxicological Science in Meeting the Challenges and Opportunities of Hydraulic Fracturing. Toxicol Sci 139, 271–283 (2014). https://academic.oup.com/toxsci/article/139/2/271/2511610 (Accessed 28 November 2017)
[lii] Chemicals used in hydraulic fracturing. United States House of Representatives. Committee on Energy and Commerce. April 2011. http://www.conservation.ca.gov/dog/general_information/Documents/Hydraulic%20Fracturing%20Report%204%2018%2011.pdf (Accessed 27th November 2017)
[liii] By US Geological Survey [Public domain], via Wikimedia Commons https://commons.wikimedia.org/wiki/File%3AHydraulic_Fracturing_Marcellus_Shale.jpg
[liv] Haswell, M. R. & Bethmont, A. Health concerns associated with unconventional gas mining in rural Australia. Rural Remote Health 16, 3825 (2016). https://www.ncbi.nlm.nih.gov/pubmed/27951725 (Accessed 22 January 2018)