PhD, DABT, Senior Consultant
Environmental regulations need to achieve a careful balance – between providing enough protection on one hand and putting too heavy a compliance burden on the other. Golder’s work on the hazards posed by a widely-used but little-understood class of compounds is helping protect human health and the environment while helping to manage remediation costs.
Since their introduction in the 1920s, alkanolamines (or amines) have been used to process natural gas that is considered “sour” due to high levels of hydrogen sulfide (H2S). Introduced into the gas stream, the amines isolate the H2S so the sulfur can be removed and possibly sold as a byproduct. The amines can be recycled and used again. It is a well-established process – amines are used in about 95% of gas “sweetening” operations in the US.
This system works well provided the amines stay inside the closed loop and do not escape, which might happen through a catastrophic break in a pipeline or through a slow drip from a leaking pipe, weld, valve, or other part of the system. In the case of a spill or leak, established soil and groundwater protection regulations come into play. Mitigate measures to achieve compliance can involve excavating and treating soil, as well as treating surface water and groundwater, that may have had contact with the fugitive amines.
Regulations must evolve as we gain knowledge and experiences in the most effective and practical solutions. By working hand-in-hand with regulators and proposing scientifically sound solutions, we can gain clarity and identify where compliance can be streamlined without sacrificing the intended benefits of regulatory oversight.
As risk-based regulations are developed, they can be somewhat incomplete in their consideration of all potential contaminants of concern. For example, when the type of amine released doesn’t actually have a toxicity value, the tendency is to revert to a worst-case scenario and therefore raise the standard of care to its highest level. This can be a sensible approach when negative effects are unknown, but once understood, proper risk-based remediation levels need to be established to address the actual issue correctly. Rather than defaulting to an assumption of the highest level of toxicity, as in the case of methyl diethanolamine (MDEA), which is an amine commonly used in sweetening operations, and applying the available toxicity value for diethanolamine (DEA), when deriving risk-based clean-up levels. The toxicity of MDEA and DEA are considerably different and, as such, using DEA standards to represent MDEA can add considerable costs and efforts and may not effectively address the issue.
Those efforts might include having to excavate and treat a larger volume of soil than is really needed, which can be costly. It also causes disturbance to the soil, as well as carbon emissions involved in the remediation. This can be a problem where the requirement is to remediate the soil down to the level of the groundwater – and in arid parts of the western US, that water table can be 60 meters (200 feet) or more below the surface.
Read-across analysis helps bridge data gaps
So how is it possible to develop risk-based levels for managing a substance for which the toxicological properties have not yet been determined? This question matters not just for managing the effects of amines, but also for a host of other compounds without regulatory agency-derived toxicity values or adequate toxicity data.
Golder’s work on MDEA and other amines has involved the “read-across” technique, which uses the idea that chemicals that have structural similarities are likely to have similar physical-chemical and toxicological properties – as well as similar environmental fate and health effects.
By examining available data on the chemical/physical properties as well as mode of action and toxicity of a well-understood compound – called the surrogate — that can be shown to be similar, read-across techniques help fill in the data gaps in the properties of one that is not as well understood. This information can then be used to help establish, in a transparent way, what regulatory procedures will adequately protect human health and the environment, without unnecessary effort and cost.
Currently, Golder is using read-across techniques to learn about MDEA and another amine called DIPA to understand their chemical structure, the way they exert their toxicity, as well as the toxicity end points it affects such as the liver and the central nervous system. The team is also looking at each compound’s physical-chemical properties including how it mobilizes, its solubility and how it moves in groundwater.
Putting the knowledge to work
Golder will now begin the process of presenting our proposal and negotiating with regulators on establishing updated toxicity values for MDEA and DIPA, which were derived using the read-across techniques.
To assist oil and gas company personnel in the field, we are developing a practical guide or flowchart to guide their work. This will provide immediate direction on what to do if a leak of a particular type of amine is discovered including instructions on matters such as spill response measures, the appropriate chain-of-custody procedures to follow, and which type of laboratory should test the samples.
A greater understanding of how read-across techniques, which have been developed and used in roughly the past ten years, can be effectively and efficiently applied to other compounds will continue to benefit the industry. With new compounds being constantly developed, there is a need for a transparent, reliable, systematic approach that will help determine toxicity information for compounds where this information is currently lacking.
Constituents of concern to environmental regulators such as Per-and Polyfluoroalkyl Substances, collectively known as PFAS, are a prime example. Read-across techniques can help improve understanding of these compounds, quickly develop toxicity information for the PFAS with minimal toxicity information and establish methods to effectively and efficiently regulate remediation efforts.
As understanding of read-across techniques grows and are more widely accepted by regulatory authorities, environmental scientists will have an expanded toolbox for protecting the environment and human populations while allowing industry progress.