Bob Palmer, Chairman, Alachua County EPAC comments on Health Consultation on Surface Soils near the Gainesville FL Superfund Site

3 Sep

TO:                  Randy Merchant, Florida Department of Health

FROM:            Bob Palmer, Chairman, Alachua County EPAC

Joe Prager, Publisher of

SUBJ:              Comments on June 6, 2001 Health Consultation on Surface Soils near the

Gainesville FL Superfund Site

DATE:            July 12, 2011

These comments relate to the June 6, 2011, Florida Department of Health Consultation entitled “Surface Soil in Stephen Foster Neighborhood Yards and Areas North, East, and South of the Koppers Hazardous Waste Site”. The public comment on this document ends on August 8, 2011, and I would ask that you share these comments, as appropriate, with other State and Federal officials and the public.

My principal comment relates to the descriptors of risk routinely utilized by FL-DOH in many of its risk assessment documents.  These terms appear on page 9 of the most recent Koppers health consultation:

1 in 10 (10-1)                “very high” increased cancer risk

1 in 100 (10-2)              “high” increased cancer risk

1 in 1,000 (10-3)           “moderate” increased cancer risk

1 in 10,000 (10-4)         “low” increased cancer risk

1 in 100,000 (10-5)       “very low” increased cancer risk

1 in 1,000,000 (10-6)    “extremely low” increased cancer risk

There are three problems with FL-DOH’s risk terminology.

First, DOH doesn’t use the terms consistently in its analysis.  For instance, on page 10, the risk of developing cancer from dioxins in Stephen Foster soils is characterized as 20 x 10-6.  On page 12, the risk of developing cancer from PAH’s in off-site soils is cited as 70 x 10-6.  It’s not clear why categories like:

1 in 10,000 (10-4)         “low” increased cancer risk

1 in 100,000 (10-5)       “very low” increased cancer risk

are listed on page 9 if FL-DOH doesn’t actually use them in the actual analysis.  Reducing every risk value to some multiple of 10-6 might leave the mathematically unsophisticated reader with the impression that all risks are in the “extremely low” category.  That may not be FL-DOH’s intention, but I can think of no good reason why your department would develop a scale that it doesn’t actually use in its analysis.

Secondly, wording in the text and in the tables at the end of the document appears to be inconsistent; the effect of this disconnect seemingly minimizes the potential carcinogenic impact of dioxins on children in the Stephen Foster neighborhood.   Table 4 cites the estimated maximum child dose for dioxin as 10-5 ug/kg/day and the estimated maximum adult dose as 10-6 ug/kg/day.   On page 10, the theoretical increased lifetime cancer risk from these exposures is described as follows:

“Cancer risk – People who incidentally ingest (swallow) very small amounts of surface soil with the highest TCDD-TEQ levels in the Stephen Foster neighborhood yards over an entire lifetime (70 years) are at a “very low” increased theoretical risk of cancer (Table 4). Multiplying the maximum TCDD-TEQ dose (0.0000001 μg/kg/day) by the EPA cancer slope factor (150 μg/kg/day-1) results in a “very low” additional increased theoretical cancer risk of 20 in a million or 20 x 10-6

No mention is made on page 10 of the increased theoretical risk of cancer for children.  If one multiplies the maximum TCDD-TEQ dose for children by the EPA cancer slope factor, the result is an increased theoretical cancer risk that is 10 times as large (2 x 10-4) as the risk cited on page 10 (2 x 10-5).  To a lay reader it is not at all clear why you appear to be only citing risks for adults and why the apparently greater risks to children are not described in the body of the report[1].

Thirdly, and most importantly, no rationale is given for the categories of risk (e.g. “extremely low” and “very low”) listed on page 9.  These vague terms, which are used at least eight times in the body of the report, have no regulatory significance, but their repeated usage leaves the impression that they do.  Rather than clarifying risk, the use of terms like “extremely low” clouds the reader’s understanding of the regulations that govern cancer risk.  For example, a cancer risk of 9 x 10-5 would be characterized by FL-DOH as “very low”.  An alternative descriptor for this level of risk would be “90 times more carcinogenic than the level which triggers regulatory action for soils under Florida law”.  The phrase “very low” is bland and reassuring, but the phrase “90 times more carcinogenic”, however alarming, is in fact more accurate.  In attempting to avoid frightening the public, DOH appears to be using language that veers too far in the other direction.  Your terminology comes off not as reassuring but as obfuscating.

At a minimum, any DOH document that uses the descriptors on page 9 should include a section explaining their derivation and their relationship to State and Federal regulations.  Ideally, the entire scheme should be replaced by one that more clearly reflects the scientific and regulatory reality of cancer risk.  Perhaps values between 10-6 and 10-5 could be labeled “of some concern” and so forth.  Or perhaps the risk level should simply be given (e.g. “1 chance in 45,000”), leaving the interpretation to the reader.  Either of these alternatives would be preferable to the current system, which perpetuates the disconnect between DOH’s characterization of risk on the one hand and State and Federal regulatory triggers on the other.

[1] Page 10 does cite the risk “over an entire lifetime” so perhaps your calculations reflect the fact that individuals will only receive the higher dose for a limited time (i.e. during the childhood years).  Nevertheless, it seems to me that a child exposed to 10 times the adult dose will achieve an adult’s 70-year risk within 7 years, and will then have an additional 63 years to accumulate further dosages.  In any event, the discussion of exposures for children and adults is confusing and falls short of your goal of clearly informing the public about probable risks.

DOH report:

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