Probabilistic Risk Assessment of Polycyclic Aromatic Hydrocarbons (PAHs) in Produced Water

ABSTRACT

The produced water extracted during oil and gas production includes formation water, injected water, small volumes of condensed water, and any chemical added during the oil/water separation process. Produced water contains both organic and inorganic constituents, and several studies have been conducted in the past to assess their risk. The toxicity and persistence of polycyclic aromatic hydrocarbons (PAHs) in produced water is of particular environmental concern, but there are very few studies on human health risk assessment from PAHs of produced water. This article summarizes the results of a conservative human health risk assessment approach for PAHs in produced water discharges to the marine environment. Due to the absence of available toxicity data for PAHs, the cancer slope factors were determined by using the relative potency factors (RPF) and Toxicity Equivalency Factors (TEF). Using the concentration distribution factors, the maximum cancer risks to humans were predicted in the range of 4.07 × 10⁻⁷ to 2.95 × 10⁻⁶. The 95th-percentile values show that the risks are well within the acceptable limits.

Key Words:

• human health risk
• produced water
• PAHs
• probabilistic risk

ACKNOWLEDGMENT

Financial support provided by the Petroleum Research Atlantic Canada and the Collaborative Research and Development program of the Natural Sciences and Engineering Research Council (PRAC/NSERC CRD) is appreciated. The authors are also very grateful to the anonymous reviewers for their invaluable suggestions to improve the quality of the manuscript.

Notes

¹ OGP (2002).

^2a Utvik et al. (1999),

^2b Utvik (1999).

³ OGP (2005).

⁴U.S. Environmental Protection Agency: B2: Probable human carcinogen; D: Not classifiable.

⁵International Agency for Research on Cancer: 2A: Probable human carcinogen; 2B: Possible human carcinogen; 3: Not classifiable; N/A: Not available.