[CPEO-BIF] RE: Another View on Vapor Intrusion Risks from Cambridge Environmental

["Kenneth S. Kamlet" <kkamlet@hotmail.com>]

Reproduced below are comments, shared with me by the authors, that were sent 
by Cambridge Environmental Inc. to the NYS Department of Health on the 
latter's draft Vapor Intrusion Guidance.

While they express a point of view not frequently seen on this ListServ, I 
find the comments provocative and thought they would be of interest to 
readers.  I look forward to seeing the responses and rebuttals likely to 
ensue.

Ken Kamlet

-----------------------------------
   Kenneth S. Kamlet, Esquire
   Director of Legal Affairs
   Newman Development Grp., L.L.C.
   3101 Shippers Road, P.O. Box 678
   Vestal, New York 13851-0678
   607-770-1010, FAX: 607-770-3482
   kkamlet@hotmail.com

======================
Cambridge Environmental Inc
58 Charles Street Cambridge, Massachusetts 02141
617-225-0810 FAX: 617-225-0813 www.CambridgeEnvironmental.com

May 31, 2005

New York State Department of Health
Bureau of Environmental Exposure Investigation
Flanigan Square, Room 300
547 River Street
Troy, New York 12180-2216

Dear Colleagues,

We write to comment on the February 2005 Public Comment Draft of Guidance 
for Evaluating
Soil Vapor Intrusion in the State of New York (hereinafter ?Vapor Intrusion 
Guidance?) as
developed by the Department of Health (DOH). Our comments derive from our 
collective
experience is assessing potential risks to human health, and in particular 
our experience in
evaluating vapor intrusion at sites in Massachusetts and other states.

Implementation of the Vapor Intrusion Guidance will likely add considerable 
costs to remedial
investigations at contaminated sites. Many factors influence the vapor 
intrusion pathway,
making it difficult to evaluate and mitigate with confidence. The goal of 
meeting stringent riskbased
standards with a high degree of certainty at all sites is, in our opinion, 
not justified or
practical with respect to the vapor intrusion pathway. Simply put, the costs 
of the approach
proposed in the Vapor Intrusion Guidance far outweigh the benefits it might 
provide. We
recommend that the Vapor Intrusion Guidance embrace more reasonable risk 
management
policies that will still protect human health with an ample margin of safety 
but at the same time
reduce the costs it would otherwise create.

Simple Cost-Benefit Analysis

Many of the lowest (and hence most stringent) risk-based concentrations for 
contaminants are
based on a maximum permissible increase in the risk of getting cancer. For 
example, DOH?s
target risk concentration of 5 ug/m3 for trichloroethylene (TCE) is 
motivated by concerns over
potential cancer risks. Typical limits on allowable incremental cancer risk, 
however, are not
very valuable in economic terms. Assume, for argument?s sake, that a 
decision is made to
mitigate an incremental cancer risk of 10 in 1,000,000 due (theoretically) 
to vapor intrusion into
a residence, and this risk is averted for four people. Assuming that these 
cancers might lead to
premature death, and that value of a human life is about seven million 
dollars (an arguable value,
but typical of that used by economists), the monetary benefit of the 
mitigation is:
4 × (10 ÷ 1,000,000) × $7,000,000 = $280

This value is probably an overestimate of the actual benefit, given that the 
methods and
assumptions used to estimate risk of cancer (especially for compounds not 
known to cause the
disease in humans, either at all, or at levels reasonably close to ambient) 
are typically biased to
over-predict. With regard to TCE, despite abundant epidemiologic study of 
this compound, TCE
has not been established to cause cancer in humans, even at very substantial 
levels of exposure in
workplace air in decades past, let alone at the vastly smaller levels of 
exposure of interest for the
current topic (see, for example, Lash et al., 2000, available at
http://www.whitehouse.gov/omb/inforeg/2003report/325-4.pdf ). Moreover, the 
typical costs of
evaluating and mitigating the vapor intrusion pathway are much greater than 
this ?benefit.?
Samples analyzed by U.S. EPA Method TO15 cost about $400 each. Many samples, 
collected
over numerous locations and points in time, would be required at a typical 
site to satisfy the data
confidence goals implied in the text of the Vapor Intrusion Guidance. Adding 
the costs of
collecting the samples and interpreting the results, vapor intrusion 
investigations may easily
require $10,000 or more, even at relatively simple sites. Remedial options 
are also likely to cost
more than the economic benefit of the mitigation. The installation of a 
simple subslab
depressurization system is of the order of $2,000. At $400 per sample 
(analysis alone), longterm
monitoring is likely to be even more costly, although we suspect this option 
will be pursued
infrequently relative to active mitigation options.

Our overall point is that economic benefits alone do not justify the costs 
of aggressive
implementation of the Vapor Intrusion Guidance. There are admittedly other 
benefits (e.g.,
?peace of mind? issues) that are not easily quantified, but there is a one 
to two orders of
magnitude disparity between the costs of investigating and mitigating the 
vapor intrusion
pathway and the economic benefits of its risk mitigation. In this case, risk 
management
decisions should not err excessively on the side of caution. Put another 
way, the Vapor Intrusion
Guidance need not (and should not) be constructed in a manner that 
identifies through exhaustive
investigation all situations in which the vapor intrusion pathway could ? 
under any hypothetical
circumstances ? present risks in excess of stringent criteria. Rather, we 
recommend that the
Vapor Intrusion Guidance embody a philosophical approach that pursues 
situations where vapor
intrusion is plausibly a significant threat.

Evaluation of Background Risk

Consideration of background air quality also brings into question the cost 
effectiveness of the
Vapor Intrusion Guidance. Mitigating vapor intrusion at contaminated sites 
will do little to
decrease the potential health risks of breathing indoor air, which contains 
many different
chemicals due to both natural conditions and emissions from indoor sources 
such as heating,
smoking, cooking, and use of consumer products. The consideration of a 
risk-based
background, i.e., a background based on the aggregate risk of all chemicals, 
as opposed to
[footnote: The crude risk (unadjusted for complicating factors) equals 
21,000 deaths per year
divided by the approximate U.S. population of 300,000,000 times 70 years.]  
independent consideration of each individual chemical, is also a relevant 
perspective in
residential settings. Radon, a pollutant that enters homes naturally through 
vapor intrusion, is
typically present at concentrations that correspond to incremental cancer 
risk levels that are one
to two orders of magnitude greater than the target risk levels deemed 
significant by most state
regulatory agencies. Based on a recent study, the U.S. EPA estimates that 
exposure to radon
leads to 21,000 deaths each year (see
http://www.epa.gov/radon/images/radon_pooling_studies.pdf), which crudely 
corresponds to a
risk of death of 5 in 1,000 over a 70-year lifetime.1 Mitigating vapor 
intrusion risks of the
magnitude of 0.001 to 0.01 in 1,000 (1 to 10 in a 1,000,000) makes very 
little difference in
overall risks to indoor air pollution (except, of course, in the case where 
mitigation
simultaneously decreases the risk to radon exposure, which should not be 
used to justify the
costs of mitigating the contaminants of interest to vapor intrusion). Thus, 
if radon is used as one
of the chemicals in the definition of background indoor air risk, efforts to 
limit vapor intrusion
risks to stringent levels are not an effective means to reduce the overall 
risk.

Even if background is evaluated on a chemical-by-chemical basis, the 
approach presently
proposed in the Vapor Intrusion Guidance is both too simplistic and overly 
protective (in
consideration of our previous discussion of costs and benefits). For 
chemicals such as benzene,
indoor air background is complicated by many factors that render inadequate 
its characterization
by a single distribution of measurements. There are distinct differences in 
indoor air
concentrations of benzene in the homes of smokers and non-smokers, and 
within residences with
attached and separate garages. In this case, there is an important risk 
management decision
implicit in the Vapor Intrusion Guidance ? that of whom should be protected, 
and to what degree
of confidence.

It may be impractical to differentiate background indoor air quality based 
on consumer
preferences (e.g., smokers vs. non-smokers), but the choice of percentiles 
that determine
acceptable background levels is an explicit risk management decision. As 
proposed in the Vapor
Intrusion Guidance, the DOH defines typical indoor air background 
concentrations for a
contaminant to be within 25th and 75th percentile values of a series of 
measurements taken in
homes with no known vapor intrusion issues. By doing so, the DOH implies 
that the upper 25th
percentile of the measurements represent levels above acceptable background. 
Put another way,
one in every four homes might be expected to exceed the acceptable 
background level,
irrespective of vapor intrusion. As such, indoor air measurements that seek 
to cases in which
vapor intrusion is potentially significant will demand further investigation 
25% of the time. At
the very least, these cases will demand additional investigation to 
determine the source of the
indoor air contamination (which in many cases can be expected to be related 
to indoor sources,
and not to vapor intrusion), and may lead to unnecessary mitigation efforts.

The choice of using the 25th and 75th percentile values to define the 
background range also
obscures some important aspects of the background data. For example, the 
table of background
values in the draft Vapor Intrusion Guidance lists a background range from 
<0.25 ug/m3 to <0.25
ug/m3 for TCE in residences, i.e., suggesting that TCE was not detected in 
the indoor air of
homes. However, the underlying data set found that TCE was in fact detected 
in indoor air in
19% of the homes tested. Hence, despite the general tendencies of decreased 
use of TCE, it
appears to remain present in some households (perhaps because of its 
presence in some
consumer products), but this fact is not reflected in the proposed 
background definition.
Again, given our previous discussion of costs, we recommend that the DOH 
assign a broader
range to acceptable percentile range used to define background conditions, 
and hence eliminate
up front a higher degree of ?false positives? in which background indoor air 
conditions may be
mistakenly identified as potential vapor intrusion issues. As an example of 
a similar need to deal
with this same issue, the Massachusetts Department of Environmental 
Protection (DEP), in
constructing its GW2 groundwater standards based on the vapor intrusion 
pathway, assigns
background concentrations at the 90th percentile of data distributions, 
thereby introducing
hypothetical misidentification of background in only one of ten cases. We 
recommend that DOH
expand its definition of background in a similar manner.

Risk-Based Concentrations

The proposed Vapor Intrusion Guidance assumes a priori that vapor intrusion 
is a potentially
significant issue and demands the collection of data in essence to confirm 
or disprove this
assumption. Given the difficulty of dismissing the significance of the 
pathway (potentially
requiring extensive measurements), the assignment of stringent risk-based 
concentrations as
target levels is yet another factor that will lead to costly investigations 
and mitigations. Again,
questions should be asked from the standpoint of risk management. Given the 
benefits to be
derived from an aggressive policy on the vapor intrusion pathway (which by 
our previous
arguments are limited economic gains and small reductions in the overall 
risks of background
indoor air quality), does it make sense to base target concentrations on 
overly conservative
interpretations of toxicologic or epidemiologic data?

The implications of developing risk-based concentrations are especially 
apparent with respect to
trichloroethylene (TCE), for which the DOH has established a target 
risk-based concentration of
5 ug/m3. The rationale for assigning this low value ? barely detectable by 
current methods ?
stems from a recent draft health assessment document in which the U.S. EPA 
has presumed that
TCE is a potent carcinogen with no safe level of exposure. This presumption 
is not supported by
the evidence, and has not been finalized or otherwise made part of U.S. EPA 
health risk
assessment policy (as evidenced, for example, by the fact that the 
?Carcinogenicity Assessment?
section of U.S. EPA?s Integrated Risk Information System (IRIS) entry for 
TCE was withdrawn
in July 1989, and has yet to be replaced. Consequently, we do not feel the 
scientific evidence
justifies the regulation of TCE at the 5 ug/m3 proposed by the DOH, 
especially when viewed in
the context of other uncertainties associated with the vapor intrusion 
pathway.

In summary, the approach proposed in the Vapor Intrusion Guidance implies an 
aggressive
approach toward investigating and mitigating potential risks to human health 
Due to the risk
management decisions embodied in the Vapor Intrusion Guidance, actual risks 
to human health
will be overpredicted, and considerable resources will be devoted toward 
reducing risk levels
that will have little public health benefit. While we endorse the pursuit of 
cases in which vapor
intrusion is likely to be of significant consequence, we suggest that the 
Vapor Intrusion
Guidance be modified to focus on a smaller number of sites, in part by 
making changes in the
approaches to interpreting background and toxicological data suggested 
above.

Thank you for your consideration of our comments.

Sincerely,

Stephen G. Zemba, Ph.D., P.E.
Senior Engineer

Laura C. Green, Ph.D., D.A.B.T.
Senior Scientist and President


_______________________________________________
Brownfields mailing list
Brownfields@list.cpeo.org
http://www.cpeo.org/mailman/listinfo/brownfields