Technical Guidance 08: Review of the current international approaches to total petroleum hydrocarbon assessment

Coffey Environments Pty Ltd was commissioned by the Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE) to prepare a detailed review of the background to the respective international approaches on total petroleum hydrocarbons.  This was designed to ascertain the basis to decisions on differences in the use of the Total Petroleum Hydrocarbon Working Group (TPHCWG) hydrocarbon fractions that are used internationally but are subject to adjustment in some cases.  This was an outcome associated with discussions arising from the Technical Working Group and Petroleum Project Advisory Group meetings held in Melbourne on 20 November 2007 and 29 November 2007 where the outcomes of the working document on total petroleum hydrocarbons were presented.

The objective is to provide a detailed review of the background to respective international approaches on total petroleum hydrocarbons in order to ascertain the basis to decisions on differences in the use of the TPHCWG fractions and associated toxicological, fate and transport data and the specified scope of works including an examination of:

• the US Agency for Toxic Substances and Disease Registry (ATSDR)’s position on total petroleum hydrocarbons (TPH), based on their current documentation
• the Netherlands, Institute of Public Health and the Environment (RIVM)’s use of an extended range of TPH fractions based on recent publications
• the UK Department of Environment’s use of an extended range of TPH fractions as presented in regulatory publications
• the Canadian Council of Ministers of the Environment (CCME)’s use of a reduced series of TPH fractions as detailed in regulatory publications, and
• the New Zealand (NZ) approach in the use of AIP fractional approaches that are a reduced group of fractional ranges as presented by the NZ Ministry for the Environment (MfE).

The review strategy encompassed a literature review of regulatory publications in this area and related documentation and email correspondence to a range of international regulatory scientists, consultants, researchers and academics through personal and public networks.

A consistency in terms of the background information used in the development of TPH fractional approaches was identified with regional adjustments including:

• the use of risk-based techniques of assessment common to all areas
• staged approaches in the site assessment of petroleum-hydrocarbon impacted land
• the use of specific indicator substances such as carcinogens (benzene, benzo[a]pyrene) and commonly encountered contaminant non-carcinogens such as ethylbenzene, toluene, xylenes and naphthalene, followed by TPH fractions, and
• the assessment of TPH fractions undertaken either concurrently with, or sequentially to, the indicator substances.

Table 7 summarises the information relevant to each national position across these issues.

Selection of fractions and data for toxicological evaluation and fate and transport characteristics has consistently been drawn from the work of the TPHCWG.  The adaptation of that work, however, has differed from minor adjustment to reduction of the numbers of TPH fractions using various methods including, in some cases, adjustment of toxicological endpoints.  In addition, although some commonality exists for TPH fractional analytical procedures each agency has examined or documented specific procedures for evaluation or implementation.

ATSDR has directly captured the TPHCWG fractions with an extension of the aromatic equivalent carbon (EC) range of >EC5-EC8 of the TPHCWG to aromatic EC>5-EC9 to capture all the BTEX substances in this range.  This has also been adopted by RIVM.  The ATSDR then use the 13 fractions for fate and transport evaluation and the exposure assessment with consolidation of ranges into the seven toxicity fractions for evaluation.  RIVM is also consistent with this approach in deriving their updated maximum permissible risk values.

The UK Environment Agency has undertaken extensive consultation on TPH approaches and has extended the TPH fraction range to also include aromatic   >EC35-44 for both aliphatic and aromatic ranges and a combined >EC44-70 range.  The implementation of their recommendations is currently under consideration.

The CCME and New Zealand MfE have adopted a reduction in TPH fractions in their documentation embodying weighted averaging approaches and assumptions on the distribution of aromatic and aliphatic components.  The CCME presents its approach using a combination of TPHCWG data and product composition in conjunction with regional evaluation of fresh product in terms of aromatic and aliphatic components to determine this distribution.  The New Zealand basis uses an emphasis on specific indicator substances and a special case for PAHs in diesel in reducing dependence on the assessment of TPH aromatics.  The weighting procedure for the aliphatic ranges, however, is not detailed.  The NZ MfE has also undertaken a consultation phase and is currently reviewing its position on TPH assessment based on consultation outcomes.

The international perspective as presented for these agencies is one of dynamic flux with a number of agencies currently reviewing their position on the approach to TPH.  The CCME and RIVM positions appear the most consolidated, incorporating both human health and eco-toxicological evaluations.  The ATSDR position has not changed and, although a huge amount of documentation has been generated in the United States, jurisdictional uptake has varied considerably with an apparent diversity of approaches.  In all cases regional considerations have factored significantly in the process of determining suitable frameworks.