Explosives

[Ted Henry <thenry@umaryland.edu>]

Greetings:

When trying to pull together some comparison criteria for a particular
community, I stumbled across an interesting point in some risk based
concentration tables produced by EPA region III. I had noticed that the
screening value for a DNT mixture was much lower than the the criteria for
the two individual DNT (dinitrotoluene) compounds listed. Additionally, I
noticed that the outcome of concern for the mixture was carcinogenic while
for the separate compounds it was noncarcinogenic. When I asked for
verification from the EPA I received the following response.

 To answer Ted's question regarding DNT compounds, only DNT mixtures --
containing both 2,4-DNT and 2,6-DNT -- appear to be carcinogenic in lab
animals. Currently, there is no evidence to support that either compound
alone is carcinogenic. (Apparently, the presence of both compounds
results in the type of cellular damage associated with the initiation or
promotion of cancer. This mechanism has not been observed after
administration of the individual DNT compounds.) Therefore, the
RBC for DNT mixtures is based on carcinogenic endpoints, while the
respective RBCs for 2,4-DNT and for 2,6-DNT are derived from non-cancer
endpoints.

While this was new to me with regard to DNT, it is not surprising. I
bring it to your attention because it shows the great deal of work left
to be done in the field of toxicology and how difficult it is to predict
the effects of mixtures, which is usually the case is in groundwater
contamination.

Sincerely

Ted Henry
CHAPP Center (Community Health Assessment and Public Participation)
Program in Toxicology
University of Maryland