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Mortality from soft tissue sarcomas in agricultural workers (1972–1981)
Chemosphere, Vol.16, Nos.8/9, pp 2101-2106, Printed in Great Britain
1987
0045-6535/87 $3.00 + .OO Pergamon Journals Ltd.
MORTALITY FROMSOFT TISSUE SARCOMASIN AGRICULTURAL WORKERS (1972-1981) *R. Kilpatrick a, J. Knoweldenb and D. Martinc a: Department of Medicine, University of Leicester, UK b: Department of Community Medicine, University of Sheffield, UK c: Ministry of Agriculture, Fisheries and Food, Harpenden Laboratory, UK ABSTRACT - Mortality from soft tissue sarcomas has been measured in agricultural workers over the decade 1972-81.. Comparedto overall national rates there was no increased incidence of death from this cause in either men or women employed in agriculture.
Soft tissue
sarcomas are a group of
rare malignant
tumours derived mainly from mesenchymal
elements. Their aetiologies are unknown, but a possible association with occupational
exposure to
2,4,5-trichlorophenoxy acetic acid (2,4,5-T) and related phenoxyacid herbicides was f i r s t suggested by clinical observations reported from Sweden ( I ) .
Two case-control
studies,
also
conducted in
Sweden, claimed that the risk of developing a soft tissue sarcoma was increased approximately 6-fold following exposure to phenoxyacid herbicides f o r more than I day (2,3). Supporting evidence has been provided by reports of soft tissue sarcoma cases among industrial workers in the United States of America who were involved
in
the
2,4,5-T herbicides (4-9). In contrast,
production of trichlorophenol and its derivatives, other epidemiological
evidence indicative of a causal relationship between soft
studies
tissue
have failed
sarcomas and prior
including
to
find
any
exposure to
phenoxyacid herbicides (10-14). However, when reviewing the data then available Coggon and Acheson concluded in 1982 that there was sufficient evidence to suggest a biological association between phenoxyacid herbicides (or other contaminants) and soft tissue sarcomas (15). Should such a causal relationship exist i t would be expected that the incidence of soft tissue sarcomas among occupationally exposed individuals would have increased in recent years and now be in excess of the very low
incidence
levels
present
in
the
general population.
As the phenoxyacid
herbicides have been used in agriculture and forestry in the United Kingdom f o r almost 40 years the present study was i n i t i a t e d to examine cancer mortality data in order to establish whether there has been any increase in the incidence of soft tissue sarcomas among farm and forestry workers. METHODSAND RESULTS The Office of Population Censuses and Surveys (OPCS) does not mortality
from soft tissue sarcomas; and this
mortality publications. Soft
Tissue,
this analysis.
not
publish
detailed
separately listed
in
analyses of occupational
On request OPCS supplied copies of a l l death certificates f o r residents of
England and Wales f o r which the other
cause is
cause was coded to
ICD 171, Malignant Disease of Connective and
in the ten years 1972-~981, about 3600 in number, and these form the basis f o r
Occupations were coded and identified 54 men and 2 women whose death certificates 2101
2102 indicated that they were working in agriculture or had retired from that occupation. The method adopted was to compare the the years 1972-81 with
number of deaths observed among agricultural workers in
the numbers expected at national rates for all occupations.
populations of agricultural workers by age were obtained from the and from special tabulations estimated by populations
Age-specific
death rates
were derived from the OPCSMortality for
the
of
To do this the the 1971 Census
for 1981 supplied by OPCS. For intermediate years the populations were
interpolation.
national rates
publications
for ICD 171 for the whole male and female
Statistics
by Cause. Table I
presents these
beginning, 1972-74, and later years, 1978-80. For both males and females
there is the rise with age seen for
most malignancies.
In
1972-74 the
two sexes had somewhat
similar rates, with a trend towards higher rates by 1978-80, rather more marked for males.
The census publications c l a s s i f y occupations by two d i f f e r e n t systems, by 17 Occupation Orders and selected individual occupations, and by 23 Socio-economic Groups (SEG). Occupation Order I is Farmers, Foresters and Fisherman, and includes horticultural workers. In the other system there are three SEGs of interest:
SEG 13 Farmers - employers and managers SEG 14 Farmers - own account SEG 15 Agricultural workers None of the entries in these two systems describe precisely interested although they come near to i t .
SEGs 13,
14 and
the
population
in
which we are
15 do not include horticultural and
forestry occupations, which are part of Occupation Order I. SOCIO-ECONOMIC GROUPS 13, 14 & 15 MALES Table IX shows the number of
male population enumerated in the 10% sample census in the three SEGs, the
deaths f r o m ICD 171 over the period 1972-81, and the numbers that would be expected at
national rates in these populations.
Overall,
the observed numbers of deaths, 54, is close to the
expected number, 51.9. Over half of
these were of
retired.
disparity between information recorded at censuses and on death
Becauseof the increasing
registration for
persons o v e r the
men beyond their 65th birthday, and many were
age of retirement, less reliance can be placed on comparisons
between observed and expected numbers for these older men and therefore the main analysis in this paper is limited to men economically active under 65 years of age.
Table I Malignant Neoplasm of Connective and Other Soft Tissue -
TabXe IX Populations, Observed and Expected heaths of Men in
ICD 17~. Average Annual Mortality Rates per M i l l i o n , England and Wales
5o¢io-Economic Groups 13, 14 and 15 in En
Age (Yrs)
1972-1974 M
F
1978-1980 M
F
Age
Number Enumerated
(Yrs)
In 10% Sample
1981
15-64
40049
32786
20
22.7
65+
11573
9452
34
29,2
51622
42238
54
51.9
1.6
1.5
1.6
1.2
15-29
3,4
2.0
3.6
2.5
30-44
3.4
3.3
4.5
3.1
45-54
5.2
5.8
g.9
0.6
A ll Ages 15+
55-54
11.2
10.4
16.3
11.2
65-74
21.2
14.7
28.8
22.0
75+
28.7
23,6
41.1
28.1
6.2
6,2
8.g
7.9
All Ages
Deaths 1972-81
1971
Under 15
Obs
Exp
2103 Table I l l
shows that for economically active men 15-64 years of age in SEGs 13,14 & 15 there
were less observed deaths, 19, than might be expected on general
national
experience, 22.3. There
were few deaths below 45 years of age, but in each age group mortality experience in these SEGs was marginally below the national average. FARMERS, FORESTERSAND GARDENERS For the
alternative
present data only
occupational
classification,
by occupation order, i t was possible
to
for the economically active for the period 1972-81. The numbers of fishermen have
been subtracted from the totals
for
Occupation Order I to produce Table IV. This shows essentially
the same picture as Table I l l with 23 observed deaths to be compared with 28.5 expected at national rates Table IV Populations, Observed and Expected Deaths of Men i n Farming and Forestry Ln England and Wales with ICD 171 Males Economically Active
Table l l I Populations, Observed and Expected Deaths of Men in Socio-Economlc Groups 13, 14 and 15 In England and Wales with ICD 171 Males - Economically Active Age (Years)
Number Enumerated In 10% 5altole 1971 1981
Number 6nunterated
Deaths 1972-81
Age (Yrs)
In 10% Sample 1971 1981
Obs
Deaths 1972-81
Obs
Exp
Exp
15-29
10989
9~
3
3.3
15-29
13260
13085
4
30-44 45-64
12035 16552
9677 12962
2 14
4.2 14.8
30-44
13975
12152
2
4.2 5.0
45-64
21895
16570
17
19.3
15-64
39576
32527
19
22.3
15-64
49131
418O7
23
28.5
MORTALITY OF WOMEN The number of women actively engaged in the relevant
occupations was sma]! and gave rise to
only 2 deaths, both in the 45-59 year age group, ascribed ICD
171,
in
the
whole of the ten years
1972-81. This does not allow a detailed analysis, but as 5.1 deaths would have been expected at national rates for women there was no evidence of increased risk. Although relatively few women worked in agriculture a much larger number were married to men in these occupation, and their mortality has been analysed in Table V. The pattern that emerges is that below 60 years of age the number of deaths from ICD 171 of women married
to men in SEGs 13, 14 and
15 was 13 in the whole period 1972-81, f a i r l y close to the expected number, 10.3. Table V Populations, Observed and Expected Deaths of W ~ n i n En(Jland and WaIes (With IDD 171) Married to Hen in Socio-EconeABlc GrOups 13,14 a ~ 16 Married Women: Husbands Active and Retired Age (Yrs)
Number Enu~rated In 10% Sample 1971 1981
15-29 30-44 45-59
5384
15-59
25534
Deaths 1972-81
Obs
Exp
3745
1
0.9
10014
7985
3
2.6
10136
8231
9
6.8
19961
13
10.3
DISCUSSION From the
case control
studies
herbicides, a relative risk factor of
of
soft-tissue sarcomas and recalled exposure to phenoxyacid
6 was found (2,3).
These results along with 4 deaths from
these tumours in occupationally exposed workers in manufacturing plants in the U.S., prompted Coggan and Acheson (15) to state that there was a case to answer regarding the association.
2104 Our examination of m o r t a l i t y , as recorded by death c e r t i f i c a t i o n ,
reveals
no excess of deaths
from these tumours in individua]s working in farming, in England and Wales, over the period 1972-81. As phenoxyacid herbicides
have been used here f o r almost 40 years and assuming an incubation period
of 15-20 years, i t would be expected
that
contended that our method might
reveal
not
exposed to phenoxyacid herbicides is any duration of more than
one
an
association a
high
r e l a t i v e l y low.
ratios
now emerge. However, i t may be
in farmworkers, provided the proportion
Hardel] (2,3) measured exposure by re ca ll f o r
day, and also was unable to demonstrate a clear association between
increasing duration of exposure and tumour incidence. risk
might
risk
A s i x - f o l d increase
in
risk
was found, the
in all his papers being of this order with lower l i m i t s to the confidence intervals of
about 3. I t is thought that by Hardell's widely embracing a g r i c u l t u r a l workers in England and
definition
a
considerable proportion of
Wales would have been "exposed" in the 1950s, 1960s and 1970s.
I f we assume that only 20% of agricu|tural workers were exposed and that these were subject to three times the national m o r t a l i t y rates
the
high r i s k , 4/5ths at normal risk) would
number of expected deaths in the t o t a l population ( I / 5 t h at be
72.7,
which is s i g n i f i c a n t l y greater (P
observed number, 54. I t is unlikely, to
a three-fold
therefore, that as much as 20% of agricultural workers could have been exposed
risk.
I f more than 20% were in such contact with these herbicides the risk must
have been correspondingly
less.
On the other hand, i t can be shown by a similar calculation that i f
the risk ratio was as high as Hardel| claimed, 6, then i t is unlikely, with
only
54 deaths,
that
more than 7% of agricultural workers could have been so exposed. In the
smaller group of about 350,000 economically active men under 65 years of age there were
19 deaths comparedwith an expectation of 22.3 at national rates. a three-fo]d increase in risk such a result would be
unlikely
I f those exposed were subject to
(P
if
more than
26% were
exposed, and i f subject to a six-fold increase i f more than 11% were exposed. Similar data to those described by us were reported by Wiklund and Holm (14) from Sweden, using data
from
cancer r e g i s t r a t i o n s .
Their t o t a ] population was 354,620 Swedish men. The two
together strongly suggest that the r e l a t i v e
risk
factor
of
6
studies
found by Hardel] is not v a l i d , and
f u r t h e r confirmation was given by Balarajan and Acheson (16) using cancer r e g i s t r a t i o n data from the United Kingdom. The findings
of
this
mortality
study
cannot prove that phenoxyacetic acid herbicides
without risk, but they do cast serious doubts on the levels of risk c|aimed or on the proportion
are of
workers who could be at risk.
CONCLUSION Both the analyses by Occupation Order and by socioeconomic groups indicate that the mortality from soft tissue sarcomas of men s t i ] l active]y working in agricultural occupations is about average f o r all men in the country, i f anything a l i t t l e below the national rate. deaths from this cause among the smaller number of were less than might be expected at national
rates
women working for
women.
in
There were a very
few
these occupations, and these
Women (below 60 years of age),
married to men working in agriculture had average mortality for ICD 171. The analysis provides no evidence of an agricultural workers.
increased
mortality risk from soft tissue sarcomas in
2105 ACKNOWLEDGEMENTS The occupational coding for this with a grant from the Ministry
of
study was performed by Mr Steven Benford and Mr Hugh Thomas,
Agriculture,
Fisheries
and Food. We are grateful to Mrs Linda
Westlake for her statistical help.
REFERENCES I.
Hardell,L.
"Soft
tissue sarcomas and exposure to
phenoxyacids: A clinical
observation".
Hardel],L.,Sandstrom,A. "Case-control study: soft tissue sarcomas and exposure to
phenoxyacetic
Lakartidninge n 74, 2753-54 (1977) 2.
acids or ch]orophenols".
Br. J. Cancer. 39, 711-17 (1979)
3.
Eriksson,M.,Hardell,L.,Berg,N.O.,Moller,T.Axe]son,O. "Soft tissue sarcomas and exposure to chemical substances: a case referent study". Br. J. Indust. Med. 38, 27-33 (1981)
4.
Honchar,P.A.,Halperin,W.E. "2,4,5-T,
trichloropherol
and soft tissue sarcomas".
Lancet I,
268-69 (1981) 5.
Zack,J.A.,Suskind,R.R. "The mortality experience of workers exposed to tetrachlorodibenzo dioxin in a trich]oropherol process accident".
6.
J. Occup. Med. 22, 11-14 (1980)
Cook,R.R.,Townsend,J.C.,Ott,G.,Silverstein,L.G.
"Mortality experience of
employees exposed to
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)". J. Occup. Med. 22, 530-32 (1980) 7.
Ott,M.G.,Holder,B.B.,Olson,R.D. "A mortality analysis of employees engaged in the manufacture of 2,4,5-trichlorophenoxyacetic acid".
J. Occup. Med. 22, 47-50 (1980)
8.
Cook,R. "Dioxin, chloracne and soft tissue sarcoma". Lancet I. 618-19 (1981)
9.
Moses,M.,Selikoff,I.J. Lancet I, 1370 (1981)
10.
"Soft
Riikimaki,V.,Asp,S.,Hernberg,
tissue
S.
sarcomas, phenoxyherbicides and chlorinated phenols".
"Mortality
of
24-dichlorophenoxyacetic
2,4,5-trichlorophenoxyacetic acid herbicide applicators in Finland: First report prospective cohort study". 11.
acid
and
of an ongoing
Scand, J. Work Environ Health 8, 37-42 (1982)
Smith,A.H.,Fisher,D.O.,Gates,H.J.,Pearce,N.
"The New Zealand soft tissue sarcoma case-control
study: Interview findings concerning phenoxyacetic acid
exposure".
Chemosphere 12,
565-571
(1983) 12.
Thiess,A.M.,et a]. "Long term hazards of polychlorlnated dibenzodioxins and polychlorinated dibenzofurans". ARC Internal Technical Report No 78/001 Lyon (1978)
13.
Pazderova-Vejlupkova,J.,Lukas,E.,Nencova,M.,Pickova,J.,Jirasek, I. 2,3,7,8 tetrachlorodibenzo-p-dioxin". Prakov Lek 32, 204-09 (1980)
"Chronic poisoning
by
2106
14.
Wiklund,K.,Holm,t-E. "Soft tissue sarcoma risk J. Nat. Cancer Inst. 76, 229-234 (1986)
15.
Coggon,D.,Acheson,E.D. "Do phenoxy herbicides cause cancer in man"? Lancet I, 1057-59 (1982)
16.
Balarajan,R.,Acheson,E.D.
in
"Soft tissue sarcomas in
Epidemio] Community health 38, 113-116 (1984)
Swedish agricultural and forestry workers".
agricultural
and forestry
workers".
J.
1987
0045-6535/87 $3.00 + .OO Pergamon Journals Ltd.
MORTALITY FROMSOFT TISSUE SARCOMASIN AGRICULTURAL WORKERS (1972-1981) *R. Kilpatrick a, J. Knoweldenb and D. Martinc a: Department of Medicine, University of Leicester, UK b: Department of Community Medicine, University of Sheffield, UK c: Ministry of Agriculture, Fisheries and Food, Harpenden Laboratory, UK ABSTRACT - Mortality from soft tissue sarcomas has been measured in agricultural workers over the decade 1972-81.. Comparedto overall national rates there was no increased incidence of death from this cause in either men or women employed in agriculture.
Soft tissue
sarcomas are a group of
rare malignant
tumours derived mainly from mesenchymal
elements. Their aetiologies are unknown, but a possible association with occupational
exposure to
2,4,5-trichlorophenoxy acetic acid (2,4,5-T) and related phenoxyacid herbicides was f i r s t suggested by clinical observations reported from Sweden ( I ) .
Two case-control
studies,
also
conducted in
Sweden, claimed that the risk of developing a soft tissue sarcoma was increased approximately 6-fold following exposure to phenoxyacid herbicides f o r more than I day (2,3). Supporting evidence has been provided by reports of soft tissue sarcoma cases among industrial workers in the United States of America who were involved
in
the
2,4,5-T herbicides (4-9). In contrast,
production of trichlorophenol and its derivatives, other epidemiological
evidence indicative of a causal relationship between soft
studies
tissue
have failed
sarcomas and prior
including
to
find
any
exposure to
phenoxyacid herbicides (10-14). However, when reviewing the data then available Coggon and Acheson concluded in 1982 that there was sufficient evidence to suggest a biological association between phenoxyacid herbicides (or other contaminants) and soft tissue sarcomas (15). Should such a causal relationship exist i t would be expected that the incidence of soft tissue sarcomas among occupationally exposed individuals would have increased in recent years and now be in excess of the very low
incidence
levels
present
in
the
general population.
As the phenoxyacid
herbicides have been used in agriculture and forestry in the United Kingdom f o r almost 40 years the present study was i n i t i a t e d to examine cancer mortality data in order to establish whether there has been any increase in the incidence of soft tissue sarcomas among farm and forestry workers. METHODSAND RESULTS The Office of Population Censuses and Surveys (OPCS) does not mortality
from soft tissue sarcomas; and this
mortality publications. Soft
Tissue,
this analysis.
not
publish
detailed
separately listed
in
analyses of occupational
On request OPCS supplied copies of a l l death certificates f o r residents of
England and Wales f o r which the other
cause is
cause was coded to
ICD 171, Malignant Disease of Connective and
in the ten years 1972-~981, about 3600 in number, and these form the basis f o r
Occupations were coded and identified 54 men and 2 women whose death certificates 2101
2102 indicated that they were working in agriculture or had retired from that occupation. The method adopted was to compare the the years 1972-81 with
number of deaths observed among agricultural workers in
the numbers expected at national rates for all occupations.
populations of agricultural workers by age were obtained from the and from special tabulations estimated by populations
Age-specific
death rates
were derived from the OPCSMortality for
the
of
To do this the the 1971 Census
for 1981 supplied by OPCS. For intermediate years the populations were
interpolation.
national rates
publications
for ICD 171 for the whole male and female
Statistics
by Cause. Table I
presents these
beginning, 1972-74, and later years, 1978-80. For both males and females
there is the rise with age seen for
most malignancies.
In
1972-74 the
two sexes had somewhat
similar rates, with a trend towards higher rates by 1978-80, rather more marked for males.
The census publications c l a s s i f y occupations by two d i f f e r e n t systems, by 17 Occupation Orders and selected individual occupations, and by 23 Socio-economic Groups (SEG). Occupation Order I is Farmers, Foresters and Fisherman, and includes horticultural workers. In the other system there are three SEGs of interest:
SEG 13 Farmers - employers and managers SEG 14 Farmers - own account SEG 15 Agricultural workers None of the entries in these two systems describe precisely interested although they come near to i t .
SEGs 13,
14 and
the
population
in
which we are
15 do not include horticultural and
forestry occupations, which are part of Occupation Order I. SOCIO-ECONOMIC GROUPS 13, 14 & 15 MALES Table IX shows the number of
male population enumerated in the 10% sample census in the three SEGs, the
deaths f r o m ICD 171 over the period 1972-81, and the numbers that would be expected at
national rates in these populations.
Overall,
the observed numbers of deaths, 54, is close to the
expected number, 51.9. Over half of
these were of
retired.
disparity between information recorded at censuses and on death
Becauseof the increasing
registration for
persons o v e r the
men beyond their 65th birthday, and many were
age of retirement, less reliance can be placed on comparisons
between observed and expected numbers for these older men and therefore the main analysis in this paper is limited to men economically active under 65 years of age.
Table I Malignant Neoplasm of Connective and Other Soft Tissue -
TabXe IX Populations, Observed and Expected heaths of Men in
ICD 17~. Average Annual Mortality Rates per M i l l i o n , England and Wales
5o¢io-Economic Groups 13, 14 and 15 in En
Age (Yrs)
1972-1974 M
F
1978-1980 M
F
Age
Number Enumerated
(Yrs)
In 10% Sample
1981
15-64
40049
32786
20
22.7
65+
11573
9452
34
29,2
51622
42238
54
51.9
1.6
1.5
1.6
1.2
15-29
3,4
2.0
3.6
2.5
30-44
3.4
3.3
4.5
3.1
45-54
5.2
5.8
g.9
0.6
A ll Ages 15+
55-54
11.2
10.4
16.3
11.2
65-74
21.2
14.7
28.8
22.0
75+
28.7
23,6
41.1
28.1
6.2
6,2
8.g
7.9
All Ages
Deaths 1972-81
1971
Under 15
Obs
Exp
2103 Table I l l
shows that for economically active men 15-64 years of age in SEGs 13,14 & 15 there
were less observed deaths, 19, than might be expected on general
national
experience, 22.3. There
were few deaths below 45 years of age, but in each age group mortality experience in these SEGs was marginally below the national average. FARMERS, FORESTERSAND GARDENERS For the
alternative
present data only
occupational
classification,
by occupation order, i t was possible
to
for the economically active for the period 1972-81. The numbers of fishermen have
been subtracted from the totals
for
Occupation Order I to produce Table IV. This shows essentially
the same picture as Table I l l with 23 observed deaths to be compared with 28.5 expected at national rates Table IV Populations, Observed and Expected Deaths of Men i n Farming and Forestry Ln England and Wales with ICD 171 Males Economically Active
Table l l I Populations, Observed and Expected Deaths of Men in Socio-Economlc Groups 13, 14 and 15 In England and Wales with ICD 171 Males - Economically Active Age (Years)
Number Enumerated In 10% 5altole 1971 1981
Number 6nunterated
Deaths 1972-81
Age (Yrs)
In 10% Sample 1971 1981
Obs
Deaths 1972-81
Obs
Exp
Exp
15-29
10989
9~
3
3.3
15-29
13260
13085
4
30-44 45-64
12035 16552
9677 12962
2 14
4.2 14.8
30-44
13975
12152
2
4.2 5.0
45-64
21895
16570
17
19.3
15-64
39576
32527
19
22.3
15-64
49131
418O7
23
28.5
MORTALITY OF WOMEN The number of women actively engaged in the relevant
occupations was sma]! and gave rise to
only 2 deaths, both in the 45-59 year age group, ascribed ICD
171,
in
the
whole of the ten years
1972-81. This does not allow a detailed analysis, but as 5.1 deaths would have been expected at national rates for women there was no evidence of increased risk. Although relatively few women worked in agriculture a much larger number were married to men in these occupation, and their mortality has been analysed in Table V. The pattern that emerges is that below 60 years of age the number of deaths from ICD 171 of women married
to men in SEGs 13, 14 and
15 was 13 in the whole period 1972-81, f a i r l y close to the expected number, 10.3. Table V Populations, Observed and Expected Deaths of W ~ n i n En(Jland and WaIes (With IDD 171) Married to Hen in Socio-EconeABlc GrOups 13,14 a ~ 16 Married Women: Husbands Active and Retired Age (Yrs)
Number Enu~rated In 10% Sample 1971 1981
15-29 30-44 45-59
5384
15-59
25534
Deaths 1972-81
Obs
Exp
3745
1
0.9
10014
7985
3
2.6
10136
8231
9
6.8
19961
13
10.3
DISCUSSION From the
case control
studies
herbicides, a relative risk factor of
of
soft-tissue sarcomas and recalled exposure to phenoxyacid
6 was found (2,3).
These results along with 4 deaths from
these tumours in occupationally exposed workers in manufacturing plants in the U.S., prompted Coggan and Acheson (15) to state that there was a case to answer regarding the association.
2104 Our examination of m o r t a l i t y , as recorded by death c e r t i f i c a t i o n ,
reveals
no excess of deaths
from these tumours in individua]s working in farming, in England and Wales, over the period 1972-81. As phenoxyacid herbicides
have been used here f o r almost 40 years and assuming an incubation period
of 15-20 years, i t would be expected
that
contended that our method might
reveal
not
exposed to phenoxyacid herbicides is any duration of more than
one
an
association a
high
r e l a t i v e l y low.
ratios
now emerge. However, i t may be
in farmworkers, provided the proportion
Hardel] (2,3) measured exposure by re ca ll f o r
day, and also was unable to demonstrate a clear association between
increasing duration of exposure and tumour incidence. risk
might
risk
A s i x - f o l d increase
in
risk
was found, the
in all his papers being of this order with lower l i m i t s to the confidence intervals of
about 3. I t is thought that by Hardell's widely embracing a g r i c u l t u r a l workers in England and
definition
a
considerable proportion of
Wales would have been "exposed" in the 1950s, 1960s and 1970s.
I f we assume that only 20% of agricu|tural workers were exposed and that these were subject to three times the national m o r t a l i t y rates
the
high r i s k , 4/5ths at normal risk) would
number of expected deaths in the t o t a l population ( I / 5 t h at be
72.7,
which is s i g n i f i c a n t l y greater (P
observed number, 54. I t is unlikely, to
a three-fold
therefore, that as much as 20% of agricultural workers could have been exposed
risk.
I f more than 20% were in such contact with these herbicides the risk must
have been correspondingly
less.
On the other hand, i t can be shown by a similar calculation that i f
the risk ratio was as high as Hardel| claimed, 6, then i t is unlikely, with
only
54 deaths,
that
more than 7% of agricultural workers could have been so exposed. In the
smaller group of about 350,000 economically active men under 65 years of age there were
19 deaths comparedwith an expectation of 22.3 at national rates. a three-fo]d increase in risk such a result would be
unlikely
I f those exposed were subject to
(P
if
more than
26% were
exposed, and i f subject to a six-fold increase i f more than 11% were exposed. Similar data to those described by us were reported by Wiklund and Holm (14) from Sweden, using data
from
cancer r e g i s t r a t i o n s .
Their t o t a ] population was 354,620 Swedish men. The two
together strongly suggest that the r e l a t i v e
risk
factor
of
6
studies
found by Hardel] is not v a l i d , and
f u r t h e r confirmation was given by Balarajan and Acheson (16) using cancer r e g i s t r a t i o n data from the United Kingdom. The findings
of
this
mortality
study
cannot prove that phenoxyacetic acid herbicides
without risk, but they do cast serious doubts on the levels of risk c|aimed or on the proportion
are of
workers who could be at risk.
CONCLUSION Both the analyses by Occupation Order and by socioeconomic groups indicate that the mortality from soft tissue sarcomas of men s t i ] l active]y working in agricultural occupations is about average f o r all men in the country, i f anything a l i t t l e below the national rate. deaths from this cause among the smaller number of were less than might be expected at national
rates
women working for
women.
in
There were a very
few
these occupations, and these
Women (below 60 years of age),
married to men working in agriculture had average mortality for ICD 171. The analysis provides no evidence of an agricultural workers.
increased
mortality risk from soft tissue sarcomas in
2105 ACKNOWLEDGEMENTS The occupational coding for this with a grant from the Ministry
of
study was performed by Mr Steven Benford and Mr Hugh Thomas,
Agriculture,
Fisheries
and Food. We are grateful to Mrs Linda
Westlake for her statistical help.
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