Opinion on Risk of cancer caused by textiles and leather goods coloured with azo-dyes expressed at the 7th CSTEE plenary meeting, Brussels, 18 January 1999.
Assessment of the Report by
LGC "The risk of cancer caused
by textiles and leather goods
coloured with azo dyes"
Opinion
Questions addressed to
the Committee:
The CSTEE has been asked
to comment on
a) the assessment of the
risk of cancer caused by
textiles and leather goods
coloured with azo dyes as
described in the corresponding
Report by the Laboratory of the
Government Chemist (LGC) and
b) the general quality
of the above Report.
Opinion:
The CSTEE considers that
the LGC report reviews
adequately the situation
regarding the risk of cancer
for consumers as a result of
the use of fabrics dyed with
azo compounds and its
conclusions are in general
acceptable. The Committee
supports the Report's
recommendation that use of azo
dyes should be restricted but
a) sees no reason for
distinguishing between the 14
amines classified by the EU as
category I or II carcinogens
and the 8 amines classified by
the MAK Commission, and
considers that the aim of
minimizing or completely
avoiding their use should apply
equally to all 22 and b)
considers that such restriction
should not be subject to prior
development of validated
analytical methodology.
Justification of the
Opinion:
The Report reviews the
chemistry and toxicology of azo
dyes, their use as textile and
leather colourants and exposure
of consumers using textiles and
leather coloured in this way,
and discusses the cancer risks
associated with such exposure.
The CSTEE notes that the Report
focuses on consumer risks, even
though the wording of the
Report's objective ("To
consider the risks of cancer
caused by textiles and leather
goods which are coloured with
azo dyes") may be interpreted
as also including risks for
workers involved in the
production and handling of such
goods. Exposure of workers
involved in the production of
such azo-dyed goods is briefly
mentioned in the Report, but no
discussion of workplace risks
is included because it is
considered that risks of
occupational disease are
controlled as a result of best
current workplace practices in
accordance with health and
safety legislation. While this
approach is often used in
similar assessments, its
validity is limited in the
absence of information on
workplace compliance with
current legislation.
The main conclusion of
the Report is that, while
consumer exposure is likely to
be "very low", the associated
cancer risks give cause for
concern. Based on this
conclusion it is recommended by
the Report's authors that:
a) use of azo dyes which
have the potential to give rise
to the 14 aromatic amines
classified as Category 1 or 2
carcinogens according to
Directive 76/769/EEC should be
restricted to the lowest
possible levels or completely
eliminated,
b) validated analytical
methodology should be developed
prior to implementation of such
restrictions,
c) the socio-economic
impacts of any restrictions
should be evaluated prior to
implementation, and
d) data should be
generated to enable the
assessment of the mutagenic
potential of the remaining 8
MAK III-listed aromatic amines
and then of the remaining dyes
of interest.
In addition to its main
part, the Report includes four
Annexes consisting of
I) the conclusions of
the "European Inspection of the
Notification of New Substances"
project which suggest that a
significant proportion of new
chemicals (including dyes) may
in practice be circumventing
the notification procedure
required by Directive
92/32/EEC, hence not subjected
to the corresponding regulatory
controls;
II) the chemical
formulas of 22 aromatic amines
classified as Category 1 or 2
carcinogens according to
Directive 76/769/EEC or
Category A1 or A2 according to
the German MAK Commission;
III) a document titled
"Risk assessment for diazo
textile dyes", prepared for LGC
by Prof. I.C. Shaw; and
IV) a document titled
"Best estimate risk assessment
calculations for dermal and
oral exposure".
In its main part the Report reviews briefly but adequately the background to the use of azo compounds as textile colourants and the relevant legislation (including recent restrictions introduced in some European countries). It points out that the concern from the point of view of carcinogenic risks arises from the potential of azo dyes to undergo in vivo reductive cleavage to aromatic amines, including the 22 amines classified by the EU or the MAK Commission as proven or suspected human carcinogens. Given that the criteria (including the availability of mutagenicity data) for classification in EU Categories 1 or 2 and in MAK Categories A1 or A2 are fundamentally similar, the CSTEE considers that this concern applies equally to azo dyes which can generate the 14 EU-classified amines and to those that can generate the 8 MAK-classified ones and that any restrictions should apply to both groups of azo dyes (it is noted that the amine with CAS No. 120-71-8, classified by the MAK Commission as A2, is 6-methoxy-m-toluidine and not 6-methoxy-o-toluidine as mentioned in the Report).
The discussion of the
toxicology of azo dyes is based
on the Annex III document. As
far as non-cancer effects are
concerned, based on detailed
studies with 2 azo dyes it is
concluded that the NOAEL's for
man are likely to be of the
order of hundreds of mg/kg and
hence unlikely to be of any
concern. However, bibliographic
evidence is presented
suggesting that problems of
skin and pulmonary
sensitisation, due mainly to
azo dyes of the disperse type,
may be rarely encountered.
Furthermore, it is noted that
the animal data on which this
conclusion is based refer only
to 2 azo compounds, give only a
LOAEL and not a NOAEL, and that
no allowance for any safety or
uncertainty factors are made in
the calculations extrapolating
to man. However, given that the
Report's aim is to assess
cancer risks from the use of
azo dyes, this omission is
understandable.
The mutagenicity and
carcinogenicity of azo dyes are
discussed in the Annex III
report in some detail. No
epidemiological observations
regarding possible carcinogenic
effects of azo dyes in man are
available. Despite the fact
that only few such compounds
have been properly tested for
animal carcinogenicity,
structure-activity
considerations make it likely
that many more would prove
positive if tested. Reductive
cleavage to constituent
aromatic amines is suggested as
the most important (although
perhaps not the only possible)
mechanism of genotoxicity. The
CSTEE endorses this suggestion
and stresses that the
conclusions which follow apply
only to those azo dyes which do
undergo conversion to the
specified aromatic amines in
vivo.
The main routes of human
exposure to azo dyes identified
are a) oral ingestion, mainly
referring to the sucking of
textiles by babies and young
children, b) dermal absorption,
the route of primary concern
for consumers wearing azo
compound-dyed products, as well
as for workers in dye
production and use plants, and
c) inhalation, a route of
concern for workers in dye
production and use industries
as well as those handling newly
dyed products. Contact with
aromatic amines entering the
environment through the whole
life-cycle of azo dyes in
coloured clothes is an
additional potential source of
human exposure which is not
discussed in the Report. A
description of human exposure
to aromatic amines from sources
not related to azo dyes would
have been useful but is also
not included in the Report.
Turning to the quantitative estimation of consumer exposure resulting from leaching of dyes from fabrics, the only relevant information which appears to be available consists of data on the extractability of azo dyes from fabrics into simulated body fluids and comes from two study reports by the Ecological and Toxicological Association of Dyes and Organic Pigments Manufacturers (ETAD). These data indicate that dye extractability is generally low, with the exception of acid-dyed wool/nylon socks leaching into alkaline perspiration simulant. Taking this as a worst case situation, the total exposure of an adult over a lifetime use of a garment covering the whole body is calculated as 723 µg/kg, while that of a small child which, in addition to suffering similar dermal exposure, receives oral exposure by sucking a piece of garment is calculated at just under 13 mg/kg (a small mathematical error in the Report does not substantially alter the estimated exposure levels). It is concluded that these exposures, which are likely to be gross overestimates, are still far below the human NOAEL for non-cancer end-points. No attempt is made in the Annex III report to obtain a quantitative estimation of the cancer risks. However, the possibility that a child may be exposed to mg quantities of a potentially carcinogenic azo dye is recognised as undesirable by the Report.
undesirable by the Report.
Whereas the above calculations were based on a worst case scenario, an attempt is made in Annex IV to derive a series of "best estimates" of exposure to aromatic amines resulting from dyes leaching from fabrics to the skin of adults or children or to the mouth of babies. Employing data on the rate of leaching of various types of dyes taken from the ETAD reports and recommended values of other parameters taken from the Technical Guidance Document for Risk Assessment, and assuming 1% skin penetration, 30% azo compound conversion to amine in the skin (a figure in accordance with the limited experimental evidence) and either 100% or 1% conversion in the mouth, amine exposures in the range 9.7-20 ng/kg/day for adults and 0.48 or 48 ng/kg/day for children are estimated. These exposures are finally used to estimate cancer risks based on the unit risk value for benzidine derived by the US EPA (4.3x10-3 ng/kg/day for 1x10-6 risk). The calculated risks for all cases range from 1 in 100 to 1 in 200,000. While these calculations are likely to err on the high side, and while recognising that some azo dye-related aromatic amines are less powerful carcinogens than benzidine, the magnitude of the estimated cancer risks justifies the conclusion that there may be reasons for concern.
In conclusion, the LGC
report reviews adequately the
situation regarding the risk of
cancer for consumers as a
result of the use of fabrics
dyed with azo compounds and its
conclusions are in general
acceptable. However, the
Committee sees no reason for
distinguishing between azo dyes
capable of cleaving to the 14
EU-classified aromatic amines
and those capable of cleaving
to the 8 MAK-classified ones,
and considers that the aim of
minimizing or completely
avoiding their use should apply
equally to azo dyes capable of
generating any of these 22
amines.