Hazard Identification

Voda Petroleum, Inc., Clarksville City, Texas
Photo from website: http://www.tceq.state.tx.us/assets/public/remediation/superfund/vodaoptim/pages/voda07_jpg.htm


Chemicals present at a hazardous waste or a contaminated site can number in the tens or hundreds depending on historical activities at the location. Risk assessment at the site involves identifying the chemicals, what levels of concentration are present, and how the chemicals are being distributed through the soil, water, and/ or air.

Early investigation requires data to be collected to best help identify the chemicals and severity of contamination of the site. Data Table 14-2 on page 869 of Chapter 14 from "Hazardous Waste Management" 2nd Edition by LaGrega et al. (2001), lists some of the questions that should be answered to assist in determining the type and possibly the quantity of chemicals present on a particular site. In addition, ASTM (American Society for Testing and Materials) E 1527 and E 1903 are standards for conducting Phase I and Phase II environmental site assessments. Covered in ASTM E 1527 for Phase I investigations are:

Scope of Phase I Environmental Assessments
Speaking the Language- Terminology
Application and use of E 1527
Responsibilities
Records Review
Site Reconnaissance
Safety and Health
Interviews
Report Preparation
Dealing with the Non-Scope Issues

Copies of ASTM E 1527 can be purchased through the ASTM website at: http://www.astm.org/Standards/E1527.htm

Once the chemical of concern or most hazardous chemicals are identified, these chemicals can be used as a subset or the surrogates for the other, less harmful chemicals at the site. Doing so limits the number of chemicals that would need to be modeled in fate and transport analyses. The risk posed by the contaminated site is represented by the surrogate chemicals and are classified by:

• The most toxic, persistent, and mobile
• The most prevalent in terms of spatial distribution (the distribution of a population within an area) and concentration
• Those involved in the more significant exposures
  

An initial screening of data from all detected chemicals at a site will assist in determining the subset or surrogate chemicals. The screening process includes:

• Sorting the contamination data by medium (groundwater, soil, etc.) for both carcinogens and noncarcinogens
• Tabulate for each detected chemical the mean and range of concentration values observed at the site
• Identify the reference concentrations for noncarcinogens and slope factors for carcinogens for each potential exposure route
• Determine the toxicity score for each chemical in each medium

Here is an example of how to calculate a toxicity score for a noncarcinogen:



TS=Cmax /RfC
Where: TS= Toxicity score
CMax = Maximum Concentration
RfC= Chronic reference concentration (i.e an estimate of acceptable daily intake) RfC data can be found at: www.epa.gov/iris/

Carcinogens use a slope factors to calculate the Toxicity score, and that information can be found at www.epa.gov/iris/ as well.




Examples of how a selection of both carcinogenic and non-carcinogenic chemicals are ranked can be found on page 871 of Chapter 14 from "Hazardous Waste Management" 2nd Edition by LaGrega et al. (2001). Assigning a Toxicity Score to certain chemicals helps prioritize and rate the chemicals into subset and/ or surrogate groups.

LaGrega also lists additional considerations, should further screenings be necessary. They include:

Mean concentration
Frequency of detection Mobility
Persistence in the environment
Chemicals associated with site operation
Treatability

This is just a brief look at hazard identification of contaminated sites. One day, there may be a cure-all technology to clean up contaminated sites in place. Researchers at Carnegie Mellon University are using nano-particles to clean up contaminated sites. In addition, I believe that contaminated site hazard identification will become somewhat less burdensome than in previous decades because of the development of satellite accessible images such as the one included below. These types of photographs were rare in the late 20th century, but now they allow the public to peer onto sites almost anywhere in the world with use of a personal computer. Locations of barrel yards and sludge ponds can easily be identified.

Southern Maryland Wood Treatment Plant- Taken from the EPA website on 1/29/2009