xvEPA Total Petroleum Hydrocarbons at Motor Fuel Release Sites What are Total Petroleum Hydrocarbons? Hydrocarbons are a large class of chemicals composed of hydrogen and carbon atoms. Petroleum hydrocarbons typically originate from crude oil and are the primary compounds that make up common motor fuels like gasoline and diesel. Total Petroleum Hydrocarbons (TPH) analyses measure the quantity of hydrocarbons within a carbon range in soil, groundwater, or soil vapor. The three common TPH ranges used in underground storage tank (UST) cleanups are gasoline range organics (GRO), diesel range organics (DRO), and motor oil range organics (ORO). TPH and Leaking UST Site Assessment Site assessment reports for a motor fuel release may include chemical analysis results for TPH. While TPH refers to petroleum hydrocarbons, many analytical methods do not differentiate the source of carbon compounds. Test results must be interpreted carefully, as nonpetroleum hydrocarbons (e.g., naturally occurring organic materials such as plant roots) can be captured in a "TPH" analysis. Why does the EPA measure TPH at motor fuel release sites? TPH is a relatively inexpensive and useful screening test for assessing cleanup operations but is rarely used on its own for making final decisions. At motor fuel release sites, the TPH testing can help determine: • The location of the petroleum release underground. • If there is a potential petroleum vapor intrusion (PVI) issue. • If light nonaqueous phase liquids (LNAPL) are likely to be present. • If workers are at risk of direct exposure to LNAPL during excavation and remediation and require the appropriate personal protective equipment (PPE). • Total mass of petroleum for designing remediation systems or determining how long it may take the petroleum to degrade naturally. • Permitting requirements for soil disposal. • How much biodegredation of the petroleum has occurred. Gasoline Range Organics (GRO) - Hydrocarbons that have 6-10 carbon atoms. Diesel Range Organics (DRO) - Hydrocarbons that have 10-28 carbon atoms. Oil Range Organics (ORO) - Hydrocarbons that have 20-40 carbon atoms. 0 8 GRO Carbon Number 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 DRO ORO Gasoline Jet fuel Diesel Heating Oils Heavy Fuel and Lubricating Oils GAS VAPOR LIQUID OIL THICK OIL SEMI-SOLID SOLID Figure 1: TPH testing ranges and petroleum product classification based on number of carbons. The TPH testing ranges (blue) as defined by the EPA 8015D analytical testing method compared to the approximate ranges of select petroleum products (green). Predicted physical state is indicated by the bottom gradient bar. E PA-510- F-23-008 December 2023 ------- A rOA Total Petroleum Hydrocarbons at Motor Fuel WtrM Release Sites Can a TPH measurement tell me if my health is at risk from a motor fuel release? The federal underground storage tank program does not use TPH to assess health risk for motor fuel releases because TPH can include hundreds of compounds of different toxicities and concentrations. States are typically the primary implementing agencies, except in Indian country, and may have their own TPH requirements, so please refer to your state's petroleum program. Variation between samples makes it difficult to establish a relationship between toxicity and a TPH value. Instead, for motor fuel releases we measure chemicals of concern, such as: BTEX (benzene, toluene, ethylbenzene, and xylene), napthalene, MTBE (methyl tert-butyl ether), and lead scavengers like ethylene dibromide (EDB) and 1,2-dichloroethane (DCA) which exhibit greater toxicity, solubility, and volatility than other compounds in motor fuels. These chemicals of concern generally drive cleanup decisions. When they are addressed, threats from the other compounds that are less toxic, volatile, soluble, or mobile are typically addressed as well. Identifying the chemicals of concern and the health effects of heavier petroleum products like bunker fuels and crude oil is the subject of ongoing research. More information on the potential toxicity and health effects of petroleum mixtures can be found in the Agency for Toxic Substances and Disease Registry's public health statement on total petroleum hydrocarbons.1 Does the EPA remove all petroleum as part of a site cleanup? Most often, the majority of a petroleum release is removed when the underground storage tanks and surrounding soil are removed from the ground. In many cases, it is not necessary to remove all of the remaining petroleum from a site to protect human health and the environment. The primary goal when cleaning up motor fuel releases is to address contamination as needed to eliminate exposure of petroleum to surface water, drinking water, and air. Cleanup procedures focus on petroleum that is migrating in groundwater, threatening surface water, or drinking water, or volatilizing into the air. Petroleum that is locked in place in the ground where there is no pathway for it to travel to a receptor is not a primary concern. Over time, the trapped petroleum will break down from the action of natural bacteria and other biochemical reactions. For more information on the process by which contaminants can break down in the environment as well as how these processes can be monitored, please refer to the EPA's guide for monitored natural attenuation.3 Resources 1. ATSDR. (1999). Public Health Statement Total Petroleum Hydrocarbons. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service. 2. ITRC (Interstate Technology & Regulatory Council). 2018. TPH Risk Evaluation at Petroleum-Contaminated Sites. TPHRisk-1. Washington, D.C.: Interstate Technology & Regulatory Council, TPH Risk Evaluation Team, https://tphrisk-l.itrcweb.org. 3. EPA (2012). A Citizen's Guide to Monitored Natural Attenuation. Washington, D.C.: Office of Solid Waste and Emergency Response. E PA-510- F-23-008 December 2023 Contaminants at Petroleum Release Sites Fuel Additives (oxygenates and lead scavengers) Non-site Releases of Petroleum Hydrocarbons / Petroleum Release\ (can include other naturally occurring and/or / Site Contaminants \ anthropogenic hydrocarbons) y* Wt Degradation Products (metabolites) Individual Petroleum Constituents (e.g., BTEX) Figure 2: Contaminants found at a petroleum release site. TPH does not include all possible contaminant and includes compounds not from the release. BTEX (included in the Individual Petroleum Constituents) represents a portion of contaminants within TPH. Reprinted from the Interstate Technology and Regulatory Council.2 ------- |