How the assessment was done

The Assessment was a collaborative effort of technical experts from the National Industrial Chemicals Notification and Assessment Scheme (NICNAS), the Commonwealth Scientific and Industrial Research Organisation (CSIRO), and the Department of the Environment and Energy.

The Assessment drew on technical expertise in risk assessment, chemistry, toxicology, ecotoxicology, hydrogeology, hydrology, geology and natural resource management.

The Independent Expert Scientific Committee on Coal Seam Gas and Large Coal Mining Development (IESC) provided independent advice and critical review at key points in the development of the Assessment.

Experts from Australia, the United States Environmental Protection Agency and Health Canada reviewed the Assessment and found it and its methods to be robust and fit-for-purpose.

The Assessment involved reviewing the scientific and technical literature and knowledge base, identifying the chemicals in use, developing new models and methodologies, and assessing the human health and environment risks of using the chemicals in coal seam gas extraction.

The Assessment is made up of 14 reports and reviews.

The Assessment involved reviewing the scientific and technical literature and knowledge base, identifying the chemicals in use, developing new models and methodologies, and assessing the human health and environment risks of using the chemicals in coal seam gas extraction.

Some of the methods had to be developed specifically for the Assessment. These methods can be applied in future risk assessments of chemicals proposed for use in coal seam gas extraction.

Several preparatory steps were needed before the human health and environmental risks of chemicals used in coal seam gas extraction could be assessed.

The first step in the Assessment was to review the scientific and technical literature about coal seam gas extraction to collate what was already known about how chemicals are used in the process and the potential risks to human health and the environment.

NICNAS, CSIRO and the Department of the Environment and Energy conducted the literature reviews.

The reviews covered five topics:

• how people could come into contact with chemicals during coal seam gas extraction and human health risk assessment methods – see the Human health implications review for details
• the environment into which chemicals could be released and methods for assessing risks to the environment – see the Environmental risks review for details
• integrity of coal seam gas wells and how fractures grow in coal seams after hydraulic fracturing – see the Hydraulic fracture growth and well integrity review for details
• what chemicals occur naturally in coal seams and how they may be mobilised following hydraulic fracturing – see the Geogenic contaminants review for details
• potential contamination of shallow groundwater by chemicals used in drilling and hydraulic fracturing – see the Identification of potential pathways to shallow groundwater review for details.

See the Summary literature review for an overview of the literature reviews.

The second step in the Assessment was to identify 113 chemicals used in coal seam gas extraction in Australia between 2010 and 2012 from a survey of industry and publicly reported information of chemicals used in coal seam gas extraction.

During this phase of the Assessment, researchers also gathered information about how the chemicals were used during the coal seam gas extraction process and in what quantities.

See the Identification of chemicals report for more details.

The third preparatory step was to develop models to show how chemicals might move from where they are released (most likely during an accidental leak or spill) to where humans and the environment could come into contact with them.

To do this, scientists identified the physical pathways the chemicals could travel along – for example, being washed off a surface into a stream or soaking into the soil and travelling through shallow groundwater.

The modelling stage also involved predicting the concentrations of chemicals that people or the environment could come into contact with, if the chemicals were released. Simple calculators were developed by CSIRO researchers to estimate predicted concentrations of chemicals in soil, shallow groundwater, rivers, and wetlands. Given the uncertainties involved, these predictions were designed to overestimate, rather than accidentally underestimate, the likely concentrations. For example, as some chemicals move through shallow groundwater they can ‘stick’ to soil particles, considerably reducing the concentration of chemical that humans or the environment might come into contact with, but the models did not take this into account. This ‘conservative’ approach is standard international best practice and ensures that any risks are not overlooked.

The models are described in detail in the:

• Human and environmental exposure conceptualisation report
• Environmental exposure conceptualisation report
• Predicted environmental concentrations report.

The web based software developed by CSIRO researchers is also available:

• CSIRO’s Dynamic Software Tool - Predicted Environmental Concentrations in Soil, Groundwater, River and Wetlands

Before the human health risk assessment was performed, NICNAS assessed whether each of the chemicals was harmful (hazardous) to human health in its pure, concentrated form. This hazard assessment involved reviewing international studies and laboratory results in international and national databases.

Fifty-seven of the 113 chemicals were identified as harmful in their pure, concentrated form. This is because a risk arises only if humans come into contact with a chemical and at a high enough concentration to cause harm. For example, concentrated hydrochloric acid can be harmful if swallowed, spilled on the skin, splashed into the eye, or if people breathe the vapours. A chemical that is harmful in its pure, concentrated form may not necessarily cause harm when used in coal seam gas extraction at lower concentrations. State regulatory controls and industry practices on the use of drilling and hydraulic fracking chemicals are used to ensure that these risks are minimised. The Assessment looked at these chemicals in specific scenarios in the coal seam gas extraction process to identify the risks to human health. A risk arises only if people could come into contact with a high enough amount to cause harm. For example, the public is unlikely to come into contact with concentrated hydrochloric acid used for coal seam gas extraction and is therefore not at risk of harm. Coal seam gas workers, on the other hand, may handle concentrated hydrochloric acid and companies are required by law to take precautions against their workers coming into contact with it.

Results of the human health hazard assessment are detailed in the Chemicals of low concern and the Human health hazards of chemicals reports.

NICNAS also identified what the largest dose of a chemical could be before it would cause harm to human health. This dose (the ‘largest harmless dose’) was used later in the risk assessment.

NICNAS undertook the human health risk assessment. The first step in the risk assessment was to develop scenarios informed by the scientific literature and on-ground experience (through the industry survey), which defined how workers or the public might come into contact with chemicals used in coal seam gas extraction.

For workers, these scenarios involved skin contact, or breathing dusts or chemical vapours or contact with spills during the transport, storage and handling of chemicals. The Assessment looked at risks to workers when involved in:

• transporting and storing chemicals
• mixing or blending chemicals to produce formulations
• injecting fluid formulations into the well
• cleaning and conducting other maintenance activities
• transporting and storing waste water (otherwise known as flowback and produced water)
• an industrial accident resulting in contact with a chemical.

The general public are very unlikely to come into direct contact with chemicals as they are not involved in the day-to-day coal seam gas extraction process. It is generally only through large-scale accidental spills and leaks that are not detected and cleaned up that people could come into contact with the chemicals.

The Assessment looked at risks to the public in the following events:

• a bulk spill occurs during transport of a chemical to a well site and it is not notified to the authorities, closed off to the public, or cleaned up, then a chemical enters surface water (such as a river) that is used for drinking, washing or swimming
• a bulk spill occurs at a work site from a surface storage tank or pond and it is not detected, notified or cleaned up, then a chemical enters shallow groundwater or surface water that is used for drinking, washing or swimming
• a long-term underground leak occurs from a waste water storage pond and it is not detected, notified or cleaned up, then a chemical enters shallow groundwater or surface water that is used for drinking, washing or swimming.

These scenarios were formed using conservative assumptions. Importantly, these scenarios did not assume that legislated and standard precautions designed to protect people from chemicals were in place. These kinds of conservative assumptions are standard practice for this type of pre-mitigation assessment. For example, the scenarios did not consider that workers would be wearing personal protective equipment when handling potentially harmful chemicals though workplace health and safety laws require the use of such equipment. Similarly, the distances from the source of the chemical to where the chemical could enter the environment were considered to be shorter than they are likely to be in reality.

The second step in the risk assessment was to calculate the dose of a chemical a person might receive under each scenario. These doses are likely to be overestimated because the predicted concentration models overestimate the concentrations of chemicals and the scenarios do not take into account standard precautions which are applied to protect people from chemicals.

The final step in the risk assessment was to compare the dose a person might receive under the different scenarios to the largest harmless dose. If the dose a person might receive was smaller than the largest harmless dose, the chemical was considered unlikely to be harmful to human health. If this wasn’t the case, the chemical was considered to be potentially harmful to human health under the scenario.

For some chemicals there was not enough information to calculate the largest harmless dose. For these chemicals, risk was assessed by analysing the scientific literature and applying expert judgement on the chemical’s potential to harm human health.

The risk assessment methods and findings are described in detail in the Human health risks report.

The Department of the Environment and Energy undertook the environmental risk assessment using two methods. The method used was based on the level of information that was available for the chemical.

For chemicals with only basic information available, the risk assessment was done by compiling evidence from the international scientific literature to support an expert judgement on the chemical’s potential to harm the environment. This approach considered the behaviour of the chemicals in the environment and what harm they could cause to water- and land-based animals and plants. It also considered how chemicals were used in coal seam gas extraction, factoring in the most likely ways for chemicals to be released during the extraction process and protective measures to prevent and limit spills and leaks.

Chemicals with more information available were assessed using a different method. Scenarios were developed to show how chemicals might enter a water body such as a river, pond or lake. Potential harm to the environment was assessed by determining what effect the chemicals could have on aquatic organisms in the water body, including algae, invertebrates and fish. As with the human health risk assessment, the scenarios were informed by the scientific literature and the industry survey in the preparatory steps.

The risks to the environment were assessed for the following scenarios:

• a chemical spills during transport from a storage warehouse to the well site and the spill is not detected, notified or cleaned up
• a chemical spills from storage at a storage facility and the spill is not detected, notified or cleaned up
• a chemical spills from storage at the well site and the spill is not detected, notified or cleaned up
• a chemical spills during use and handling at the well site and the spill is not detected, notified or cleaned up
• waste water containing a chemical spills during use or management of the waste water and the spill is not detected, notified or cleaned up
• waste water containing a chemical leaks from storage pond or tank and the leak is unreported
• waste water containing a chemical is reused for dust suppression
• waste water containing a chemical is reused for irrigation.

The second step in this method of risk assessment used the predicted concentration models and the above scenarios to calculate the concentrations of a chemical that the aquatic animals and plants might come into contact with. In keeping with the very conservative approach taken in this assessment, the models were designed to overestimate the concentration of a chemical that animals and plants might come into contact with.

The final step in this method of risk assessment was to compare the concentrations of chemicals that animals and plants might come into contact with under different scenarios to the largest harmless concentration. If the concentration animals and plants might come into contact with was smaller than the largest harmless concentration, the chemical was considered unlikely to cause harm to the environment. Otherwise, the chemical was considered to be potentially harmful to the environment.

This method used a staged approach with increasingly detailed consideration applied to those chemicals that were more likely to be a potential concern for the environment. Chemicals found to be safe were screened out at an early stage. The first stage used generic assumptions about extraction sites and worst-case scenarios for the quantities of chemicals potentially entering the environment. Where detailed information was unavailable the chemicals could only be assessed at this earliest, most conservative level of testing which was designed to overestimate risk. The chemicals were classed as potentially harmful at this level, but further information and testing would be required to determine the actual level of risk. Two more stages of testing were more specific to the conditions of actual extraction sites and the quantities of chemicals likely to be in use.

Both methods of assessing risks to the environment, and their findings, are described in detail in the Environmental risks report.

The Assessment was a complex project of Australian Government partners, resulting in 14 reports and reviews.

Read about the public health, workers’ health or environment findings.

Read the Assessment Overview for a summary of the Assessment and its methods and findings.