[OEM] Flight Attendant Breast CA Debate, BMJ

[Joel Baumbaugh <baumbaug@nosc.mil>]

	RADSAFERS,

	I just received this from another list I'm on.  Yet one more retrospective
cancer-type study that "drags in" radiation as a possible cause - and who
knows, they may be right...but I'd "prefer" to believe the pesticide
theory...jb

	Joel Baumbaugh (baumbaug@nosc.mil)
	SSC-SD

>BMJ 1998;316:1902 ( 20 June )
>Letters
>http://www.bmj.com/cgi/content/full/316/7148/1902?ijkey=turQI3lCE6q.Y
>
>Risk of breast cancer is also increased among retired US female airline cabin
>attendants
>
>EDITOR
>An excess incidence of breast cancer has been reported among Finnish1 and
>Danish2 airline cabin attendants (standardised incidence ratio 1.9 (95%
>confidence interval 1.2 to 2.2) and 1.6 (0.9 to 2.7) respectively). In a
>retrospective cohort survey of retired flight attendants from one US airline
>we also found an excess incidence of breast cancer (standardised incidence
>ratio=2.0 (1.0 to 4.3)) (unpublished data).
>
>Neither of the previous reports identified a cause for this excess incidence.
>One suggested that, on the basis of estimated exposures, radiation could
>account for an excess incidence of only 10%.1 Another study said that
>radiation could be responsible for the excess by acting as a cancer promoter
>but provided little corroborating evidence.3
>
>We suggest that exposure to dicophane (DDT), an organochlorine pesticide used
>to rid airplanes of insects in the 1950s to 1970s, may be a risk factor for
>breast cancer. According to a recommendation by the World Health
Organisation,
>on certain international flights DDT was to be sprayed throughout the
aircraft
>from a single use, hand operated aerosol dispenser by a flight attendant
after
>the doors were closed before takeoff, while air ventilation was limited. This
>may have resulted in substantial inhalation and dermal exposure to DDT for
the
>person operating the aerosol.
>
>See web-site for rest and for replies.
>
> , . , . , . , . , . , . , . , . , . , . , . , . , . , . , . , . , . , . , .
>' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` `
>
>BMJ 1999;318:125 ( 9 January )
>Letters
>http://www.bmj.com/cgi/content/full/318/7176/125/a#B1-1
>
>Risk of breast cancer among female airline cabin attendants
>
>Response (1)
>Findings may have been due to exposure to cosmic radiation or recall bias
>
>We agree with Wartenberg and Stapleton that dicophane (DDT) is one of the
>possible aetiological factors for breast cancer in female airline cabin
>attendants.1 Two other factors (exposure to cosmic radiation and recall bias)
>also merit attention.
>
>We are not told how the cases and controls were selected or matched in their
>survey. The exposure data should be only data up to the date of diagnosis for
>flight attendants in whom breast cancer was diagnosed (cases) and data up to
>the date of pseudo-diagnosis for controls (the date on which the breast
cancer
>was diagnosed in the cases). The cabin attendants with breast cancer would
>have stopped flying because of illness, and controls would have continued to
>fly; this would distort the measurement of exposure to cosmic radiation.
>Moreover, the cabin attendants with breast cancer would probably have had
>fewer flights in the year before the diagnosis owing to the undiagnosed
breast
>cancer. Ideally, exposure should be measured until the year before diagnosis
>to avoid this bias. The breast is the organ most sensitive to radiation
>carcinogenesis in postpubertal women,2 and hence cosmic radiation cannot be
>ruled out as a potential factor in the aetiology of breast cancer. A cohort
>study of Canadian air pilots showed an increased risk of acute myeloid
>leukaemia, the type of leukaemia induced by exposure to radiation
>(standardised incidence ratio 4.72 (90% confidence interval 2.05 to 9.31)).3
>
>Recall bias needs to be considered in any study in which exposure is measured
>after a disease has been diagnosed or an event has occurred.4 In the case of
>exposure to DDT, recall bias could have led to the non-significant
increase in
>risk that Wartenberg and Stapleton found. Because of the strong link between
>pesticides and cancers, flight attendants with breast cancer would have been
>more likely than controls to recall pesticide spray. It is always
important to
>verify the records, if they are available, to measure their agreement with
>reported exposure in a proportion of cases and controls.
>
>Although the point estimate for exposure to DDT that Wartenberg and Stapleton
>report is high (odds ratio 2.2), the wide confidence interval (0.4 to 10.9)
>suggests that recall bias could account for the observed odds ratio. We agree
>with the authors' suggestion that large studies will be the way forward to
>determine the role of DDT in breast cancer among airline attendants. These
>studies should also explore the joint effect of DDT and cosmic radiation.
>
>P Badrinath, Specialist registrar in public health medicine.
>Sam Ramaiah, Director of public health medicine.  . Walsall Heath Authority,
>Walsall WS1 1TE Badrinathp@ha.walsall-ha.wmids.nbs.uk
>
> , . , . , . , . , . , . , . , . , . , . , . , . , . , . , . , . , . , . , .
>' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` `
>
>Response (2)
>Large European studies are now being carried out
>
>...The frequency and magnitude of exposures to pesticide are unknown but
>probably limited. To our knowledge, pesticide spraying was practised only on
>international flights to a few destinations. Exposure of Finnish flight
>attendants has certainly been rare and is unlikely to have contributed to our
>findings. ...
>
>In our view, the strongest factors that have been shown empirically to affect
>risk of breast cancer among cabin crew are parity and age at first birth....
>
>Anssi Auvinen, Senior scientist.
>STUKRadiation and Nuclear Safety Authority,
>Helsinki, Finland
>
>Eero Pukkala, Epidemiologist.
>Finnish Cancer Registry,
>Helsinki, Finland
>
>Maria Blettner, Scientist.
>International Agency for Research on Cancer, Lyons, France
>Anssi.Auvinen@stuk.fi
>
> , . , . , . , . , . , . , . , . , . , . , . , . , . , . , . , . , . , . , .
>' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` ' ` `
>
>Authors' reply
>
>We did not address several issues in our letter because of space limitations.
>The study design that we used was a retrospective cohort postal survey of
>members of an organisation of retired flight attendants from one American
>airline. As Badrinath and Ramaiah suggest, selection bias, follow up bias,
and
>recall bias could all have occurred. With regard to selection bias, we were
>more likely to have omitted flight attendants who developed breast cancer (or
>died) than healthy flight attendants owing to their lack of continued
>involvement in organisations for flight attendants. In terms of follow up
>bias, the suggestion that we should have adjusted flying times seems logical,
>but all of the women who developed breast cancer either received the
diagnosis
>several years after stopping work or reported that they continued to work
>after diagnosis.
>
>Therefore we do not believe that our method underestimated exposure to
>radiation differentially, although we also believe that radiation may have
>been a contributing factor to the breast cancers.
>...
>
>We disagree that there is little evidence that organochlorine pesticides
are a
>risk factor for breast cancer. Results in the literature are mixed, but
>several studies currently under way were designed to test the hypothesis of a
>link between DDT and breast cancer more specifically than those already
>conducted. We recognise that reproductive factors are likely to contribute to
>the risk in our population (parity, age at first birth, age at menarche, age
>at menopause), but our sample was too small to assess this effect directly.
>
>Overall, our preliminary study was too small to rule out or confirm any risk
>factor for breast cancer among flight attendants....
>
>Daniel Wartenberg, Associate professor.
>Cecile Pryor Stapleton, Doctoral student.
>Environmental Health Division,
>Environmental and Occupational Health Sciences Institute,
>Piscataway, NJ 08855, USA
>
>
>--
>Gary Greenberg, MD       Duke FM, IM, Occupational & Env Medicine
>Sysop / Moderator Occ-Env-Med-L MailList  Gary.Greenberg@duke.edu
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