August 28, 1995
Mr. Lowell R. Fowler
High End Systems, Inc.
2217 West Braker Lane
Austin, TX 78758
Dear Mr. Fowler:
I have reviewed the copy of the report prepared by Consultech
Engineering Company for Actors' Equity Association on the health
effects of glycol-based fogs used in theatrical productions. As
you know, I have extensively examined the research data base on
these glycols, and am familiar with their toxicology. There are
numerous flaws with the "scientific" analyses provided in the
Consultech report. Thus, my previous conclusions that these fogs
are safe when generated by High End Systems machines and used
as directed remains unaltered.
The toxicology of the glycols themselves will, of course, be
similar for all fog machines. These glycols are hygroscopic and
at high concentrations will have a drying effect on the nose,
eyes and throat. Physically active performers will likely experience
more of these effects. However, these effects are transient, and
rapidly reverse once exposure stops. No permanent injury will
result, and thus it is not perceived as a health risk.
The Consultech report focuses on two main areas. First, the
results of chemical analyses of the fog fluids indicating the
presence of degradation products that may be toxic, and second
the results of health effects surveys on fog exposed and non exposed
performers. I will deal with each of these areas separately, plus
a discussion of general points raised in the report.
General Points
(page numbers refer to those
in the Consultech report)
Glycol-based fogs are often referred to as smoke, although they
do not consist of combustion products. Despite this obvious difference,
the Consultech report equates glycol vapors with cigarette smoke
(page 3 and page 9). Cigarette smoke is clearly irritating and
contains literally thousands of different chemicals. Such a comparison
is both misleading and inappropriate.
Concerns are voiced (page 4) about equating effects upon the
respiratory system in animals with those in humans since their
respiratory systems differ and animals lack many of the sensitivities
of humans. This argument suggests that animal studies would not
provide valuable toxicologic and other biomedical information
prior to studies in humans. This is clearly not true as animals
are well established as adequate models. There are respiratory
differences between humans and some animals that might limit the
conclusions that could be drawn. Fortunately, however, the most
important studies on glycol-fogs have been done in monkeys and,
because some of these glycols were for a time used as "air sterilizers"
in sick rooms, also in humans. The toxicology data has firmly
shown no adverse effects other than drying actions. In fact, because
of the disinfectant activity, lung diseases were lower in exposed
groups.
It is indicated on page 6 that "a large number" of complaints
have been received from performers exposed to fogs. This is a
very imprecise description. How many? How many relative to the
exposed population and to control populations? Were they unsolicited
complaints or were they received in response to the concerns voiced
by Actors' Equity?
It is indicated on page 6 that Consultech has provided technical
assistance for 3 litigations. Thus, this company is would appear
to have a conflict of interest.
The issue is raised that there is an absence of information
on potential interactions between the combinations of chemicals
used in these fogs (page 8). This is, in many respects, a spurious
argument. Unexpected interactions are always a possibility; and
one that is difficult to dismiss. However, some of the fog fluids
contain only one chemical. Most others, only two. The two chemicals
mainly used (propylene glycol and triethylene glycol) have almost
identical physical properties and no identifiable toxicities except
at enormous doses. There is no reason to expect increased toxicity
when two non-toxic chemicals from the same chemical grouping are
combined.
The toxicology of the glycols is misrepresented on page 10.
Triethylene glycol can be toxic when given intravenously, but
so can water. This compound is not a "poison". Further, the fact
that heating it to decomposition yields "acrid smoke and irritating
fumes" is irrelevant since this level of heating is not done in
fogs generated by High End Systems' machines. Finally, the statement
that "propylene glycol is an experimental teratogen" (page 10)
is wrong. All data have shown this compound is not teratogenic.
The Union Carbide study demonstrating acute toxicity of triethylene
glycol is discussed on page 49. The implication is that this study
documents a serious toxicity of triethylene glycol. This is a
misrepresentation of these data that were obtained by using extraordinarily
high fog concentrations; levels that have no relevance to the
entertainment industry and simply show that any compound will
be toxic if enough is given.
Chemical Analyses
The Consultech report states (page 7) that its thrust is on
the properties of the chemicals used in fogs, and not on any specific
product. However, all companies products are not the same, and
the methods (particularly temperature) used vary greatly. Clearly,
the lower the temperature the less likely it becomes any decomposition
products will be generated. Thus, fog machines such as those made
by High End Systems (that heat fog fluids to a maximum of 425F)
can not be equated with those used to gather the data presented
in this report, where heating to 555-700F was used.
The Consultech report makes a major issue of the tests that
showed the presence of various decomposition products. The exact
conditions of these tests are not given in the report. However,
based on the information provided, the results of these tests
would not appear to be highly relevant to the exposures humans
would receive. For example, fog fluid samples were obtained and
analyzed both before and after heating (page 11). No data are
given on the results of analyses before heating. After heating
at 555-700F various volatile organics were reported. However,
there is no information on the length of time they were heated
(and how this relates to heating in the fog machines) nor on the
levels of the volatile compounds found. The question of levels
of these compounds also applies to the analysis performed on fogs
produced by a machine (page 12). Finding these compounds in "measurable
amounts" is not particularly meaningful since modern analytical
instrumentation can detect extraordinarily low levels. It also
would be of interest to determine whether similar levels are found
in fog produced by machines from other companies, or even in the
ambient air of the theaters where they might arise from plastics,
cleaning fluids, glues, etc.
The table following page 13 that lists toxicities associated
with the degradation products appears to be designed to highlight
the dangers of these chemicals. However, levels are again critical
since virtually all of these compounds can be found in other situations
not considered a toxic hazard.
Survey
The design of the Consultech Engineering Actors' Equity Survey
is not acceptable for the development of solid scientific evidence
since it introduces massive amounts of response bias. In essence,
a survey of this type will provide the results wanted; in this
case an indictment of glycol-based fog fluids. As a result, none
of the data provided is useful. Interestingly, the report acknowledges
the presence of response bias on page 32, yet they proceed to
dismiss this major flaw and conclude that the results of the survey
support their position. In fact, the results could be construed
to invalidate their position. There were only 231 responses (of
which 98% were exposed to fogs) out of 14,133 Actors' Equity members,
with an estimated fog-exposed population of 3000. It seems clear
that very few people had any concerns.
Despite these major flaws, the Consultech report proceeds to
discuss the data in detail including "statistically significant"
results. Since there was no control population (as admitted in
the report on page 16), it is not clear how statistics could be
run in a valid fashion. Examination of the questionnaire itself
revealed leading questions that would clearly bias the results
even further. For example, question 7 was "Do you believe your
health has been affected by glycol fog?" It is virtually impossible
in a survey of this sort not to get a positive response to such
a question.
Every aspect of the Consultech Engineering Actors' Equity Survey
can be challenged. Thus, even as a descriptive survey (page 31)
it does not provide a valid indication of the health risks associated
with glycol-based fogs. The fact that this survey was "much more
detailed" than the NIOSH study (page 31) does not make it any
better. A thorough epidemiologic study is required to draw the
conclusions this report attempts to make. The available survey
results do not even begin to approach the level of sophistication
needed.
The other surveys described in this report at first appear to
have more utility. However, there is again a serious lack of controls
(or at least information on the controls). This makes it impossible
to assess whether the results have any significance. For example,
glycol fog and non-fog groups were selected. How did the performers
in these two groups compare in terms of performance characteristics
(singing, dancing, etc.) age, sex, and existing health problems.
Also, were the productions in the fog and non-fog groups comparable
in terms of theater size, theater air flow, number of performances
per week, other air-borne chemicals (i.e. smoke from gunpowder),
etc. If the sole selection criteria was the presence or absence
of fog, it is highly unlikely the two groups are comparable. It
would also be important to have a group of age/sex matched controls
who were not performers. Finally, the treatments selected for
analysis in this survey are not all reasonable. For example, acne
is not associated in anyway with the compounds of concern. Also,
why is intestinal malabsorption included? The drying effects may
well be valid, but as stated above, this is a readily reversible
effect.
I would be pleased to discuss any aspect of this report with
you at your convenience.
Sincerely,
James P. Kehrer, Ph.D.
Head, Division of Pharmacology and Toxicology
Gustavus and Louise Pfeiffer Professor of Toxicology
Dr. Kehrer is a Professor at The University of Texas at Austin |