historical research report

HISTORICAL RESEARCH REPORT
Research Report TM/85/13
1985
An evaluation of some reports on risks to
health from exposure to coal-tar-based
wood preservatives
Jacobsen M
HISTORICAL RESEARCH REPORT
Research Report TM/85/13
1985
An evaluation of some reports on risks to health from
exposure to coal-tar-based wood preservatives
Jacobsen M
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ii
Research Report TM/85/13
Report No. TM/85/13
UDC 615.9:632.95
AN EVALUATION
OF SOME REPORTS
ON RISKS TO
HEALTH FROM
EXPOSURE TO
COAL-TAR-BASED
WOOD
PRESERVATIVES
M. Jacobsen
November 1985
Price:
£10.00
(ii)
Report No. TM/85/13
I N S T I T U T E
O F
O C C U P A T I O N A L
M E D I C I N E
AN EVALUATION OF SOME REPORTS ON RISKS TO HEALTH FROM EXPOSURE
TO COAL-TAR-BASED WOOD PRESERVATIVES
by
M. Jacobsen
Institute of Occupational Medicine,
Roxburgh Place,
EDINBURGH
EH8 9SU.
(Tel. 031-667-5131)
November 1985
This report is one of a series of Technical Memoranda (TM)
published by the Institute of Occupational Medicine.
Current and earlier lists of these reports, and of other
Institute publications, are available from the Librarian
at the address overleaf.
For further information about the Institute's facilities
for research, consultancy and teaching on occupational
health and hygiene please contact the Director.
(iii)
CONTENTS
Page No.
SUMMARY
1.
INTRODUCTION
2.
NOMENCLATURE
3.
NATURE OF THE MATERIALS
4.
INFORMATION AVAILABLE ON HEALTH EFFECTS
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
5.
American studies
An investigation in Germany
A Norwegian study
A prospective study in Sweden
An association between coal tar derivatives
and scrotal cancer
Another British study
Another investigation in the Swedish Cancer
Registry
A review paper from Sweden
CONCLUSIONS AND RECOMMENDATIONS
REFERENCES
4
4
6
7
9
10
12
12
13
14
(iv)
I N S T I T U T E
O F
O C C U P A T I O N A L
M E D I C I N E
An evaluation of some reports on risks to health from exposure
to coal-tar-based wood preservatives
by
M. Jacobsen
SUMMARY
This report reviews evidence about health risks that may arise in
people exposed to coal-tar-based wood preservatives.
The limited
information available that is relevant directly to possible effects
in humans is assessed critically, from an epidemiological point of
view.
It is concluded that body contact with this class of
materials can produce inflammatory skin conditions and benign
tumours.
The need for effective action to reduce the incidence of
this kind of response is emphasised because there is fairly strong
evidence that, under adverse conditions, such benign skin lesions
may be precursors for skin cancer.
There is no evidence that coal
tar distillate fractions with boiling points below 360°C (the main
part of the mixtures used in timber preservation) can themselves
give rise to skin cancer in man.
Nor is there any evidence
pointing to an excess of lung cancer in people who have been in
contact with coal-tar-based wood preservatives.
The report
includes some suggestions for further research.
1.
1.1
INTRODUCTION
Timber may be protected from attack by insects and fungi by the
application of various chemicals, including certain coal tar
derivatives.
Commercial use of the latter materials for timber
preservation dates back to the early part of the nineteenth century.
Timber preservation is now a large-scale industry.
It has been
estimated for instance that the volume of coal-tar-based wood
preservatives us,ed in the United States alone exceeds 100 million
gallons per annum (PENTACHLOROPHENOL, INORGANIC ARSENICALS AND
CREOSOTE ASSESSMENT TEAM, 1981).
1.2
The purpose of this report is to assess limited information
currently available about possible risks to health, particularly
cancer risks, that may occur as a result of exposure to
coal-tar-based wood preservatives.
follows.
The text is arranged as
First, there is an explanation of the nomenclature that
will be used and then a summary of some essential facts about
coal-tar-based wood preservatives (sections 2 and 3).
The main
part of the report (section 4) refers in turn to various
publications and other papers.
In each case there is a brief
indication of the ground covered by the document concerned, but
these summaries do not necessarily do justice to all the data
described.
Attention is concentrated on those aspects that may be
relevant to possible effects on health arising from exposure to
coal-tar-based wood preservatives.
The accompanying comments are
directed to assessing the value of the information from this point
of view.
The comments are distinguishable in the typescript by
wider margins and reduced spacing.
recommendations are in section 5.
Conclusions and
2.
2.1
NOMENCLATURE
The products concerned are sometimes referred to collectively as
"creosotes".
That nomenclature is potentially confusing however,
because the term "creosotes" has been used variously to describe
(a)
condensates in a specific boiling range obtained from
the fractional distillation of coal tar, on their own;
or
(b) mixtures of various coal tar distillates that are
supplemented by either coal tar itself, or pitch (the
residue from the distillation of coal tar) or petroleum;
or sometimes
(c)
all crude coal tar distillation products (more usually
known as "coal tar oils").
One (older) usage of the word creosote is specific to products
derived from the distillation of wood tar.
2.2
It will be convenient therefore to retain the phrase coal-tar-based
wood preservatives (abbreviated as CTBWP) when referring to the
class of materials of .interest here, and to distinguish
specifically in the text between different types of CTBWP, when
that is necessary.
Thus "CTBWP" is to be interpreted here as
mixtures of chemicals that are derived primarily from coal tar and
that are used for the preservation of timber.
3.
3.1
NATURE OF THE MATERIALS
Commercially important CTBWP are derived from tars that are
produced by so-called "high temperature" coal carbonisation, that
is, destructive distillation of coal at temperatures exceeding
700°C.
The tars are mixtures of many hundreds of chemical
compounds, as are the products from their fractional distillation.
The latter distillates are exploited commercially for many
purposes, including the manufacture of fungicidal and insecticidal
wood preservatives.
CTBWP are based mainly on coal tar
distillates with boiling points in a range from about 205 to 360°C.
These particular fractions are known in Germany as
"Steinkohlenteer-Impragnierolen"
3.2
("coal-tar impregnating oils").
The distillation products from coal tar that are used in wood
preservatives include low concentrations of some polyaromatic
hydrocarbons that have been designated as carcinogenic in animals
by the International Agency for Research on Cancer (IARC).
CTBWP
marketed in some countries may include additives richer in some of
the higher boiling constituents of the parent tars than the
particular distillate fractions that constitute the bulk of the
mixtures.
Coal tars themselves can cause cancer of the skin in
humans (IARC, 1984).
4.
INFORMATION AVAILABLE ON HEALTH EFFECTS
4.1
American studies
4.1.1
The increased attention paid in recent years to possible health
effects from exposure to CTBWP followed an announcement in 1978 by
the US Environmental Protection Agency (EPA) of a "rebuttable
presumption against registration" (RPAR) of several chemicals used
in wood preservatives, including CTBWP.
A direct result of the
RPAR was the commissioning and production of a comprehensive study
of usage and exposure to three types of wood preservatives,
including CTBWP (PENTACHLOROPHENOL INORGANIC ARSENICALS AND
CREOSOTE ASSESSMENT TEAM, 1981).
That report also provides
estimates of the economic consequences of cancelling EPA
registration for the use of these materials.
4.1.2
Another report, commissioned by the US National Institute for
Occupational Safety and Health, describes occupational hygiene
surveys at 11 wood treating plants and at two wood preservative
manufacturing operations (TODD and TIMBIE, 1983).
The treatment
processes that were studied involved substantial usage of CTBWP and
also of other chemicals.
The authors emphasize the need for
improved work practices to further minimise worker exposure and
contact with recognised toxic chemicals.
4.1.3
4.1.4
Neither of these two reports records any clinical
or epidemiological information that might help to
assess risks to humans.
Nor does a more recent
EPA publication (ENVIRONMENTAL PROTECTION AGENCY,
1984) which summarises responses to the
announcement of the RPAR and gives notice of
intent to cancel registrations of certain
pesticide products for use as wood preservatives.
The more recent statement from the EPA (1984) recalls that the
"rebuttable presumption" for CTBWP had been based on information
indicating that these materials posed risks to health in humans,
but that the risks could not be quantified.
A qualitative
judgement had been necessary, rather than a quantitative assessment
of risk, for several reasons.
.These were the variable compositions
of the complex mixtures comprising CTBWP, possible potentiating
interactions among the chemical components, insufficient
information about human exposures, and the absence of appropriate
epidemiological data for direct estimation of risk in humans.
4.1.5
FLICKINGER and LAWRENCE (1982) describe data on workers' exposures
to CTBWP at several large American timber treatment plants and they
summarise results from cross-sectional health surveys at some of
them.
The authors conclude that the medical examinations revealed
little evidence of occupational disease except for an excess
prevalence of one inflammatory skin condition, pustular
folliculitis.
No skin cancers were observed, but one of the
plants had a high prevalence of benign tumours and of keratoses.
4.1.6
Details of the findings at four of these plants, where CTBWP were
the predominant materials used, are recorded in a report from
Tabershaw Occupational Medicine Associates.*
The report refers to
examinations of the lung, liver, kidney, blood cells and skin of
257 workers (73% of all employees at the four works).
It
concludes that the general health of those examined was good, but
that some abnormalities of the skin were probably related to
environmental exposures.
The abnormalities concerned were eczema,
keratosis, folliculitis and pigmentation.
Prevalence rates of
fungal infections, acne and benign skin tumours were unremarkable
compared to rates estimated from published data for young (35 —
44 year old) Americans generally, and there were no malignant skin
tumours, bladder cancers or lung cancers among those examined.
The
authors of the report characterise the skin abnormalities that were
seen in excess as inflammatory diseases and their sequelae, and
they comment that these conditions are recognised as potential
effects from body contact with CTBWP.
4.1.7
The absence of more serious conditions in those
examined, particularly the absence of lung or
skin cancer, will have been reassuring to the
Company and to the workers involved.
It should
be noted however that the benign skin conditions
that were seen in excess have been described
previously as pre-malignant stages in shale oil
workers who later developed skin cancer (SCOTT, 1922).
Nearly three quarters of those examined at the
* This report, kindly made available by Mr. Charles W. Flickinger of
Koppers Company Inc., is titled "1978 Cross-sectional health study of
workers at four Forest Products plants of Koppers, Inc. Volume A".
It
is dated March 19, 1979.
timber treatment plants (74%) had worked there
for less than ten years.
If there are any
occupationally related cancers in this sub-group
then they are not likely to have been diagnosed in
such a short time after first exposure.
Thus the
information provided falls far short of plausible
evidence that exposures to CTBWP are unlikely to
cause cancer.
4.1.8
No attempt was made to include ex-employees in these
cross-sectional surveys.
This feature of the
design, and the fact that the participation rate of
current employees was low (73%) are further reasons
why results from the study cannot be regarded as
rebutting a general hypothesis that exposure to CTBWP
may give rise to cancer.
4.2
An investigation in Germany
4.2.1
The physical properties of coal tar distillate fractions produced
in the Federal Republic of Germany for use in CTBWP are described
in a recent paper by WILLEITNER and DIETER (1984).
The authors
document the physico-chemical specifications for these products,
summarise animal toxicity data for the more important
constituents,
and describe results from a questionnaire survey of 90 companies
producing or using CTBWP.
Most of the companies (76/90) operated
in Germany, and the authors note that this covers virtually the
total usage of CTBWP in the Federal Republic.
4.2.2
Responses to the questionnaire showed that the total number of
workers involved in handling CTBWP at these companies was about
1800 per annum since 1970, but rather more in earlier years (ca.
2350 p.a. from 1950-1969, and perhaps 2550 at 52 of the firms who
were using CTBWP before 1950).
4.2.3
One fifth of the 90 respondents are reported to have acknowledged
the occurrence of some CTBWP-attributable skin irritations in 1980
and in earlier years back to 1950.
Most of those companies
mentioned reversible skin conditions that had occurred only in the
presence of exposure to sunlight.
None of the 90 companies
reported knowledge of any effects arising from the inhalation of
CTBWP fumes, and none recorded any CTBWP-attributable chronic
effects on health among their workers.
4.2.4
The key question that was posed to the
managements of the companies that were circulated
referred to CTBWP-attributable effects on
health.*
Thus the validity of a conclusion that
exposure to CTBWP did not cause chronic
conditions depends critically on the reliability
of managements' judgements that any such
conditions that did occur among their workers
were not associated with CTBWP.
4.2.5
In the Federal Republic at least, medical
practitioners who diagnose conditions suspected
of being related to occupation are required to
report those suspicions to the appropriate
industrial insurance association
(Berufsgenossenschaft).
The latter would
normally be expected to draw the facts to the
attention of the employer concerned.
Taken at
its face value therefore, the absence of any
acknowledgement of chronic conditions arising
from exposure to CTBWP implies that the companies
concerned were not informed of any related
insurance or compensation claims, or that they
chose not to volunteer such information (or both).
There is also a possibility that some
exposure-related cancers did occur but were not
recognised as associated with work by the
diagnosing physician.
4.2.6
The uniformly negative responses with respect to
chronic conditions in this enquiry suggests that
it is unlikely that CTBWP-associated cancers have
been common in the Federal Republic; but an
uncontrolled investigation of this kind is not an
adequate substitute for a properly designed and
independently conducted epidemiological study of
workers who have been exposed.
4.3
A Norwegian study
4.3.1
WILLEITNER and DIETER (1984) also quote results from an unpublished
cohort study in men who were employed at a Norwegian timber
impregnation plant.
The men considered were all those who joined
the company before 1970, who had completed at least 18 months
"... Gesundheitsschaden, die auf den Umgang mit Teerol zurlickzufuhren
sind".
From a copy of the questionnaire kindly provided by Dr. A.
Alscher.
service with the company before that date, and who were alive on 1
January 1953.
The 447 men meeting these criteria represented 67%
of the workforce identified at the time that the study was
undertaken.
Vital status and cancer incidence were established by
the Oslo Cancer Research Institute, as at 1 January
4.3.2
1980.
The 128 deaths observed during the 27-year period were 8% fewer
than the 139 expected on the basis of age-specific death rates for
Norwegian men generally.
There were 37 new cases of cancer
recorded during the same period as compared with 44 expected on the
basis of age-specific cancer incidence rates.
The results showed
excesses of cancers, based on very small numbers, at only two
anatomical sites:
the pancreas and the lymphatic system (3
observed with 1.8 expected and 3 observed with 1.4 expected,
respectively).
4.3.3
The investigators noted* that relatively low mortality and
morbidity in an employed population, as compared with the general
population, is not unexpected.
They drew attention also to the
fact that the latency period for cancers is often 20 years or
longer.
They concluded that no particular cancer risk was
demonstrable among employees at the Company concerned.
4.3.4
The fact that the standardised cancer incidence
ratio (84%) was considerably lower than the
standardised (all causes) mortality ratio during
the same period (92%) suggests that the
relatively lower cancer incidence among the men
studied is unlikely to have been due simply to
population selection factors of the kind common
in occupational cohort studies.
This argument
is based on the plausible assumption that the
selection factors concerned would be expected to
affect general mortality (from all causes) to at
least the same, or more likely to a greater,
extent than cancer incidence.
Thus the
investigators' cautious conclusion seems sound
and constitutes a reassurance that men who were
employed at the plant concerned after 1952 but
before 1970 were not exposed to conditions that
put them at any special risk of cancer.
* I am grateful to Dr. A. Alscher for making available a translation into
English of a brief note about these results that was addressed to the
Company concerned by the Oslo Cancer Research Institute.
4.3.5
It seems reasonable to suppose that a major
Norwegian timber impregnation plant (more than
600 employees) will have included CTBWP among
the materials used; but just how much was used
was not recorded, either by WILLEITNER and DIETER
(1984) or in the summary of the results made
available to me.
It would be useful if this
information, and perhaps some estimates of
exposure or latency periods in those studied,
were to be provided in any future publication.
4.4
A prospective study in Sweden
4.4.1
An abstract of a paper presented at a conference in 1983 records
some preliminary results from a prospective study of 123 workers
who had been employed in timber impregnation with CTBWP during the
period 1950-1980.*
to arsenic;
asbestos.
Fifty of those studied had been exposed also
eight had worked with herbicides, and seven with
There were 18 deaths in this group, of which eight were
due to cancer.
The corresponding expected mortality, based on
national age, sex and calendar-year specific rates in Sweden, was
calculated as 24.6
4.4.2
for all causes of death and six for cancer.
A sub-group was considered, consisting of individuals with at least
five years exposure exclusively to CTBWP and for whom the
observation period was sufficient to reflect a latency period of at
least 10 years.
The expected number of cancer deaths among the 21
individuals identified was 0.8, based on 248 person-years of
observation.
The number of cancers observed was three:
one
leukemia, one cancer of the pancreas and one stomach cancer.
(A
case of lung cancer, in one of those exposed only to CTBWP was not
included in the analysis of the sub-group because the period of
observation for the individual concerned was less than 10 years.)
* Axelson C, Kling H.
Dodlighetmonster hos en grupp Traimpegnerare med
kreosotexposition ("Mortality in a group of impregnation workers with
exposure to creosote").
In: Abstracts for 32nd Nordic Occupational
Hygiene Conference.
Stockholm, 19-21 September, 1983; pp 125-126.
Stockholm: Arbetarskyddsstyrelsen, Forskningsavdelningen, 1983.
10
4.4.3
The authors limit their conclusions to noting
that cancer incidence in the 123 CTBWP-exposed
workers tended to be high; and this cautious
formulation seems prudent in view of the small
number of deaths recorded so far. The
relatively high proportion of cancers observed
(8/18 = 44%, as compared with 6/24.6 = 24%
expected) is unlikely to be due simply to chance
(P < 0.05).
It is clear moreover that the
finding of some excess cancer is not to be
explained entirely in terms of exposures to
herbicides or asbestos, since the sub-group who
had been exposed occupationally only to CTBWP had
a more marked excess cancer mortality, albeit
based on a smaller number of deaths, than the
group as a whole..
4.4.4
The observations from this work stand in contrast
to those from the only other prospective study
considered here - that from Norway (section 4.3,
above).
It will be of great interest to
continue the follow-up in both groups of workers;
but note that modern therapeutic methods ensure
that skin cancers generally (including cancers of
the scrotum) are rarely fatal nowadays.
The
occurrence of such conditions are therefore not
likely to be identified in mortality studies.
From this point of view the Norwegian study is
more valuable, because it refers to cancer
incidence, not just mortality.
Perhaps the
Swedish study (Axelson and Kling) could be
strengthened by efforts to determine cancer
incidence as well as mortality.
4.5
An association between coal tar derivatives and scrotal cancer
4.5.1
A report on an investigation of scrotal cancer in relation to
occupation was published 40 years ago (HENRY, 1946).
This
referrred to some 1630 fatal cases of scrotal epithelioma that had
occurred in England and Wales during 28 years, from 1911 through
1938.
The author (S.A. Henry) estimated that this represented a
crude annual mortality rate (unadjusted for age) of approximately
4.2 per million.
He identified relatively high rates, on the same
non-age adjusted basis, for several occupations where workers were
likely to have had contact with coal tar or its derivatives.
Seventeen (1%) of the deaths identified were in men whose
occupational histories were judged by Henry as indicating contact
with "creosote oil" rather than any other putative carcinogenic
agent.
11
4.5.2
A contributor to a symposium in 1978 (J. Wahlberg) referred to
these findings and contrasted them with results from a search that
he had made of the Swedish Cancer Registry covering a 13-year
period, from 1958 to 1970.*
Wahlberg identified only 34 cases of
scrotal cancer, and he compared this with the more than 1600
described by Henry in England and Wales.
Wahlberg added that he
investigated the occupational histories of his 34 cases, with
particular emphasis on questions about possible contact with tar,
creosote, pitch, etc.
All of the respondents replied in the
negative.
4.5.3
The crude annual case rate before the second
world war in England and Wales (1630/28 = 58 per
annum) was certainly much higher than that found
more recently in Sweden (34/13 =2.6 per annum
on average).
But such comparisons make little
quantitative sense given that they refer to
quite different numbers of workers at risk.
4.5.4
The absence of any indication of an association
with coal tar or its products in Wahlberg's
series is good news, given the widespread use of
CTBWP in Sweden.
Of itself however, this
finding does not weaken the plausibility of the
association implied by Henry's results, since
working conditions generally , including those
in timber preservation, are likely to have been
very different in pre-war Britain as compared
with Sweden some 40 years later.
4.5.5
Note also that only 1% of Henry's cases were
thought to have been exposed specifically to
"creosote oil".
Such a low proportion (if it
is really attributable to CTBWP) would not be
detectable in a total of 34 Swedish cases.
* An unpublished paper: "Work problems in connection with handling
creosote impregnated utility poles", presented at a symposium "Creosote
and Utility Poles" in Akersberga, Sweden, 30-31 May, 1978.
I am
grateful to Dr. A. Alscher for providing me with a translation into
German of the Swedish text of this paper.
12
4.6
Another British study
4.6.1
HENRY (1947) also investigated the occupations of 3753 cases of
cutaneous epithelioma that had been notified to the British Medical
Inspector of Factories during 26 years, from 1920 through 1945.
"Creosote oil" was nominated as the causal agent in 35 of the
notified cases (again 1%), and Henry suggested that two other (nonnotifiable) cases were attributable to "creosote".
Twelve of the
35 notified "creosote oil" cases were cancers of the scrotum.
Fourteen of the 34 men involved had worked with "creosote oil" in
timber preservation.
4.6.2
4.6.3
-
The origin and nature of these "creosote oils" is
not specified in the report.
It seems likely
however that they would fall into the broad
grouping described here as CTBWP, since Henry
distinguishes "creosote oil" specifically from
several other causal agents listed in his
analysis (pitch, tar, tar-products, shale oil and
mineral oil.)
Of course, this study does not demonstrate that
the use of CTBWP under present working conditions
is likely to give rise to scrotal cancers.
It
does however strengthen the evidence from the
earlier study (HENRY, 1946) which indicated that
these materials are carcinogenic in humans.
4.7
Another investigation in the Swedish Cancer Registry
4.7.1
Wahlberg (see 4.5.2
above) also described his further efforts to
determine retrospectively occupational histories and possible
exposures to tar oils of some 400 cases of cancers of the skin
affecting the arms or legs.
The cases were registered over a
five-year period in the Swedish Cancer Registry.
Wahlberg
commented that there were difficulties in tracing the individuals
concerned.
Some had died "from other causes".
Others, who were
interviewed, were old and had difficulties in recalling their work
histories.
None of those interviewed gave a history indicating
any connection with tar oils and tar products;
and again, Wahlberg
contrasted this observation with the experience in England and
Wales.
The tracing rate achieved in the study was not mentioned.
13
4.7.2
It is difficult to interpret the result reported
from this imperfectly documented case study,
particularly in the absence of information on how
many of the identified cases were interviewed.
It is at least possible that the associations
described by Henry do indeed reflect in part a
causal relationship between contact with CTBWP
and cancers of the skin, but that work practices
and occupational hygiene in Sweden during recent
years have been sufficient to protect those at
risk.
It would be useful to know whether the
latter speculation is sound.
Unfortunately, the
data provided by Wahlberg do not allow even that
conclusion.
4.8
A review paper from Sweden
4.8.1
Several of the reports discussed above are cited by HENNINGSON
(1983) in a wide-ranging review article.
The topics covered
include the toxicity of CTBWP, possible health effects that can
arise before, during and after their application to timber, as well
as possible environmental problems posed by treated timber while it
is being used and during its final destruction.
The author
concludes that the environmental and occupational health risks are
not severe;
that they can be reduced or avoided by using fairly
simple protective measures;
but that urgent attention is required
to the problem of "bleeding" of CTBWP from treated utility poles a matter of particular concern to Trade Unions in Sweden.
4.8.2
This is an authoritative, balanced and
constructive discussion of health problems
associated with CTBWP.
It does not include any
original data about possible effects on health.
14
5.
5.1
CONCLUSIONS AND RECOMMENDATIONS
Body contact with coal-tar-based wood preservatives can give rise
to inflammatory skin conditions and benign tumours, particularly in
photo-sensitive individuals.
5.2
These irritating and disagreeable effects are observed in workers
handling the materials even under modern conditions in the Federal
Republic of Germany and in the United States of America and
probably also elsewhere.
This demonstrates the continuing need
for effective preventive action including engineering measures to
minimise contact with the materials, provision of protective
clothing for workers at special risk, good "house-keeping" at the
workplace, and provision of adequate eating, washing and changing
facilities to encourage high standards of personal hygiene.
5.3
The importance of these recommendations is underlined by the
fairly strong evidence, based wholly on observations in England and
Wales before the second world war, that body contact with
coal-tar-based wood preservatives can lead to malignant tumours of
the skin, including fatal cancers of the scrotum.
5.4
It is plausible, but it has not been demonstrated positively, that
the malignant skin tumours in people who worked with coal-tar-based
wood preservatives in the first half of this century occurred
because of the presence of low concentrations of high boiling
coal-tar products that occur in, or that may be added to, the
coal-tar distillate fractions used for wood preservatives.
Certainly there is no epidemiological evidence that the main
components of these mixtures ("Steinkohlen-Impragniero'le", with
boiling points less than about 360°C) can themselves cause cancer
in humans.
In particular, there is no evidence, either historical
or recent, suggesting that people exposed to coal-tar-based wood
preservatives are at increased risk of lung cancer.
15
5.5
But I am aware of only two properly designed epidemiological
studies with data relevant to possible cancer risks in workers
exposed to coal-tar-based wood preservatives during the last 40
years.
Neither of them have yet been described in a scientific
journal.
One indicates no excess cancer risk;
preliminary
results from the other are consistent with the existence of such a
risk.
future.
Both are prospective studies that could be up-dated in the
Continuation of this work and publication of results
would help to establish whether or not the kind of timber treatment
conditions common in Scandinavia during recent decades were
associated with occupational cancer risks.
question remains unanswered;
In the meantime, that
the available information is
inconclusive.
5.6
Other historically defined prospective mortality and morbidity
studies should be initiated wherever possible.
Another approach
that should be considered is appropriately designed case-control
studies based on large populations that are likely to include a
reasonable proportion of people who have worked with coal-tar-based
wood preservatives.
There are serious impediments to this kind of
research in the Federal Republic of Germany, because of statutory
rules on the confidentiality of medical information, including
causes of death.
Nevertheless, the possibilities should be
explored, perhaps by encouraging liaison between the
Berufsgenossenschaften and an independent medical research
organisation.
16
REFERENCES
ENVIRONMENTAL PROTECTION AGENCY (1984)
EPA notice of intent to cancel
registrations of wood preservative uses of pesticide products (49 FR 28666,
July 13, 1984).
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FLICKINGER CW, LAWRENCE AW (1982)
wood-preserving industry.
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437-464.
Occupational health experience in the
Proceedings of the American Wood-Preservers'
78: 11-30.
HENNINGSON B (1983)
Environmental protection and health risks in
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Holz als Roh-und Werkstoff;
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471-475.
HENRY SA (1946)
Oxford:
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HENRY SA (1947)
Occupational cutaneous cancer attributable to certain
chemicals in industry.
IARC (1984)
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389-401.
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chemicals to humans.
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Part 3:
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Risk of Chemicals to Humans.
Volume 34).
PENTACHLOROPHENOL, INORGANIC ARSENICALS AND CREOSOTE ASSESSMENT TEAM (1981)
The biologic and economic assessment of pentachlorophenol, inorganic
arsenicals, creosote.
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Wood preservatives.
Washington (DC):
US
Department of Agriculture (Technical Bulletin No. 1658-1).
SCOTT A (1922)
On the occupation cancer of the paraffin and oil workers
of the Scottish shale oil industry.
British Medical Journal;
2:
1108-1109.
TODD AS, TIMBIE CY (1983)
Industrial Hygiene Surveys of Occupational
Exposure to Wood Preservative Chemicals.
Cincinnati:
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WILLEITNER H, DIETER HO (1984)
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("Coal tar oil")
(A20115) IOM (R) ReportCov art
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