UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, DC 20460

OFFICE OF PREVENTION, PESTICIDES, AND TOXIC SUBSTANCES

DP Barcode:

Chemical: Creosote

PC Codes: 022003, 025003, 25004

Case No.: 0139

August 26, 2008

Memorandum:

Subject: Ecological Risk Assessment for Creosote: Response to Public Comments

To: Jacqueline McFarlane, CRM

Antimicrobial Division

From: William Erickson, Ph.D., Biologist

RASSB/AD

Thru: Norm Cook, Branch Chief

RASSB/AD

RASSB has reviewed the public comments on the Updated Ecological Risk Assessment for 

Creosote. Comments on the ecological risk assessment were provided by The Creosote Council; 

Beyond Pesticides; and the California Regional Water Quality Control Board, San Francisco Bay

Region. The comments and RASSB's response to those comments are provided below.

Comment (Creosote Council): EPA needs to make better and more extensive use of the 

creosote ecological studies conducted by Dr. Kenneth Brooks. The work of Dr. Kenneth Brooks 

established that use of creosote-treated wood products (e.g., marine piling) in or near water does 

not pose an environmental hazard.

RASSB Response: The studies of Dr. Brooks are evaluated in the risk assessment including 

their strengths and limitations. RASSB disagrees with the Creosote Council's conclusion that 

creosote-treated wood products in or near water do not pose any environmental hazard. Dr. 

Brooks concluded that PAHs accumulating in sediments near aquatic pilings can pose a risk to 

aquatic organisms. He concluded that such impacts might be limited to within a few meters of a 
six-piling dolphin structure in the Sooke Basin of Canada. However, the footprint of potential 

impact could be much more extensive where a larger volume of aquatic pilings was placed in an 

aquatic environment. Elsewhere, Dr. Brooks (1995) has advocated not installing creosote-treated 

aquatic structures in areas where current speeds are less than or equal to 1.0 cm/sec without 

further assessment. He stated that an individual project risk assessment should be required under 

certain conditions, including current speed, inter-piling distances, proximity to existing creosote 

structures, and other factors. Clearly, Dr. Brooks recognizes that creosote leaching from treated 

aquatic structures poses risk to some aquatic organisms. Elsewhere, as discussed in the risk 

assessment, creosote has been shown to have a significant and rapid impact on zooplankton 

communities (NOEC = 13.9 ppb), and 40-year-old creosote-treated pilings caused hatching 

failures and embryonic abnormalities in Pacific herring. Based on all available information, it is 

misleading to claim that creosote-treated wood placed in the aquatic environment poses no 

hazard to aquatic organisms.

Regarding risk to organisms in the water column of the Sooke Basin in Canada, Dr. Brooks 

states that water-column concentrations of PAHs are extremely low and not likely to be of 

concern for aquatic organisms. However, as discussed in the risk assessment, water-column 

concentrations were not measured until six months after aquatic pilings were installed. 

Microcosm studies (discussed in the risk assessment) demonstrate that water-column 

concentrations of PAHs may be sufficiently high in the first few days or weeks to cause adverse 

affects (lethal and sublethal) to aquatic organisms. 

RASSB also strongly believes that the uncertainties in extrapolating PAH concentrations in 

pristine Canadian waters in winter may not adequately reflect water-column and sediment 

concentrations that might occur in coastal Florida, Mississippi, Texas or other southern U. S.

areas with different biotic and abiotic factors. Data from these areas would provide for a more 

refined risk assessment. As discussed in the risk assessment, environmental factors such as 

salinity, temperature, pH, organic matter of sediments, water currents, tides, and others have 

been shown to influence both leaching of PAHs from treated wood and toxicity to aquatic 

organisms.

Comment (Creosote Council): In 1995 EPA waived all data requirements in favor of relying 

upon the public literature.

RASSB Response: EPA did not waive the data but did state that the registrant could use 

available published literature where appropriate. Although a field study from Canada (Sooke 

Basin) was subsequently submitted, no literature or laboratory studies have been submitted to 

satisfy the standard ecotoxicity tests required for all pesticides registered and reregistered under 

FIFRA. The data gaps are specified in the ecological risk assessment. However, RASSB

realizes the difficulty in conducting standard ecological toxicity tests for creosote, because it is a 

mixture of a variety of PAHs with differing toxicities in differing concentrations that change 

over time. RASSB believes that in lieu of standardized laboratory tests, a field or simulated 

study might better address exposure and hazard concerns for aquatic organisms. RASSB will be 

working with the Creosote Council to determine appropriate means of testing.

Comment (Beyond Pesticides): Emphasize that an endangered species determination is legally
required.

RASSB Response: The screening-level ecological risk assessment identifies the taxa (e. g., 

saltwater invertebrates) at risk, based on exceedances of the acute and/or chronic levels of 

concern. As noted in the screening assessment, a refined listed-species assessment will be 

conducted under Registration Review to assess risk to individual species in those taxa. The 

listed-species assessment will be conducted in accordance with the OPPTS' overview document1. 

http://www.epa.gov/espp/

Comment (California Regional Water Quality Control Board, SF Bay Region): Recent 

research provides additional information about the hazards that PAHs in creosote pose to fish. 

We have enclosed recent research papers on this topic.

RASSB Response: The information in these articles may be useful for further characterizing 

ecological risks of creosote, but there appears to be no new information that would change 

RASSB's risk conclusions at this time. The information will be used, as deemed appropriate, 

when RASSB conducts a refined listed-species assessment (including listed salmonids) or 

conducts any additional ecological risk assessments for creosote-treated structures.

Comment (California Regional Water Quality Control Board, SF Bay Region): Important 

data needs include sufficient aquatic toxicity data to calculate acute and chronic risks to benthic 

organisms and sufficient aquatic toxicity data to calculate chronic risk to organisms (fish, 

invertebrates, plants) inhabiting the water column in both freshwater and saltwater.

RASSB Response: RASSB agrees that additional data are needed and identifies these data gaps 

in the ecological assessment. See also RASSB's response to the Creosote Council regarding the 

data requirements.

 

1 USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide 

Programs, U.S. Environmental Protection Agency: Endangered and Threatened Species Effects 

Determinations. Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide 

Programs, Washington, D.C.