PVC AND CANCER
FAIRY-TALE
According to recent (Swedish) research, phthalates are also under suspect as a possible cause of testicular cancer.
Source: Press release of Greenpeace Germany at the opening of the Nürnberg Toy Fair, February 4, 1998.
Greenpeace Netherlands called on the Dutch environment minister Margaretha de Boer to end the production and use of PVC, and to respond to the Swedish study in a parliamentary debate on PVC
Source: ENDS Daily, January 19, 1998.
FACTS AND FIGURES
The Swedish cancer study
The hospital of Örebro (Sweden) searched for the origins of testicular cancer. This was done by sending a questionnaire to cancer patients. 148 patients replied on this questionnaire. Of those patients, 7 said that they had worked in PVC factories. From 315 non-cancer controls only 2 reported to have worked in PVC factories. The report started a lot of press coverage, especially in Sweden.
Parts of this page
The Örebro study
Review by toxicologists
Conclusion
PVC and testicular cancer
The study asked 170 testicular cancer patients for their occupational life by a questionnaire. 7 cases said that they had worked in PVC factories, against 2 from a group of 326 controls.
Besides the possible introduction of just chance by such a low number of "PVC-exposed"-cases against "PVC-exposed"-non-cases, one of the "PVC-exposed"-cases worked only three days in a PVC-factory...
The researchers conclusion was:
"In conclusion, in our case-control study of testicular cancer, a somewhat surprisingly high risk was observed for PVC plastics. The shortcomings of retrospective assesment of exposure by a self-administered questionnaire are obvious, and spurious association between PVC exposure and seminima cannot be ruled out. Therefore, our results must be regarded as hypothesis generating and they warrant further studies."
This might be the best way, but a literature study could have shown that a large scale study of PVC workers was already done in the past and didn't show excess cancers of any kind, compared to the average population.
The researchers thaught that phthalates, used as plasticiser in PVC, might be the cause, because some of these have (very weak) oestrogenic effects in some in-vitro tests. But no phthalates have shown oestrogenic effects in living animals (see our Chlorine and hormonal changes pages), even if administered continuously over two generations [25] [26]. And as far as we know, no testicular cancer was seen in animals, even when doses equivalent to 500 g/day (!) for an adult were given...
Letters of Greenpeace and other environmental groups have triggered questions of several MP's during the discussion on the use of PVC in The Netherlands.
The reaction of the Dutch environment minister Margaretha de Boer to these questions was quite clear:
The recent Swedish study on testicular cancer is only the generation of a new hypothesis and needs further investigation. This study will not influence the policy of the government now.
critical peer review of the article : "Occupational exposure to polyvinyl chloride as a risk factor for testicular cancer evaluated in a case-control study." by L. Hardell, C-G Ohlson and M. Frederickson Int. J. Cancer 73, 828-830.
- The questionnaire was a self-administered questionnaire but the questions are not presented and the context in which it was distributed is not described, neither the validation process. Increased odd ratios are presented for a so-called PVC exposure but no element are given about other possible increased odd-ratios among the other possibly subjective responses to the questionnaire. While the numbers cannot be disputed as such, they need to be put in much more accurate perspective with any other possible correlation with the other responses and possible bias. This was not done since "results of other occupations and exposures will be published elsewhere". Indeed, PVC exposure is a rather ill-defined and subjective criteria when it has to be causatively correlated with a very specific outcome such as a testicular cancer.
- In the introduction of the paper it is stated that the frequency of testicular cancer is more frequently increasing in young men. By contrast, the age of men in the study when their testicular is diagnosed is comprised between 36 and 62 years old and with a so-called latency period of 22 years! It is easy to observe among the cases presented that there is indeed a clear trend to develop a testicular cancer at a younger age but which is related NEITHER to the intensity of the so-called "PVC exposure", neither correlated to any alleged (unfounded terminology and mis-leading) "latency period". On the contrary, with the major improvement of working conditions in the industry in general, and in the PVC industry in particular, the level of exposure to "PVC" has continuously decreased over the last 25 years. Also, there is a strange skewed distribution in the form of testicular cancer in the so-called PVC exposure group described in the article. Actually the only non-seminoma in the table is presented at the age of 36 after less than 3 days of working in a PVC factory 10 years earlier.
Furthermore the IARC report on "Mortality and cancer incidence results of the European multi-centric cohort study of workers" in a study population of 12706 employees (222.746 persons years at risk) found only 3 cases of death related to testicular cancer. In the group of 2643 workers, from 4 plants in Norway and Sweden (3 VCM/PVC production plants and one processing plant) only one case was observed while 2.21 cases were expected.
| The "PVC" cancer cases |
year of
birth |
age
at
diagnosis |
period between first
"PVC exposure"
and diagnosis |
cumulated
exposure |
| 1930 |
62 |
35 |
6 |
| 1931 |
58 |
22 |
4 |
| 1939 |
50 |
12 |
12 |
| 1945 |
46 |
26 |
8 |
| 1947 |
44 |
22 |
5 |
| 1953 |
26 |
11 |
0, 0 1 (= 3 days !) |
| 1956 |
36 |
15 |
2 |
- Although the paper is said hypothetical, none of the hypothesis proposed holds on a elementary analysis:
- hypothetical link with chlorine with no argument : chlorine is not a carcinogen, can we suspect an emotional link ?
- hypothetical link with phthalates and a supposed estrogeno-mimetic effect: the basis is a publication (Jobling, Sumpter et al., 1995) which is now outdated by more recent work, including data from the same laboratory of Sumpter, demonstrating the lack of estrogenic potential of DEHP and its metabolites but also of other major phthalates used in PVC, this both in vitro and in vivo;
- hypothetical link with carcinogenicity of DEHP and cancer: DEHP is not considered as a carcinogen for humans on basis of metabolism studies in primates; furthermore, DEHP tumorigenicity of rodents is specifically associated to peroxisome proliferation in the liver, DEHP was never suspected to induce cancer of the testicles;
- hypothetical link with stillbirths : the relation with testicular cancer is simplistic and not scientifically founded and, again, purely "emotional"; furthermore the hypothesis of 1987 relating stillbirths and PVC was never confirmed by any further correlative data.
The Örebro study results are at least very discutable. The political abuse of this study by groups like Greenpeace has nothing to do with science, only with their political agenda.
You are at level one of the Chlorophiles comment pages
Created: February 15, 1998.
Last update: May 2, 1998.
Welcome page
Home Page of the Chlorophiles
Stillbirths and chlorinated drinking water
For any comment on this or other pages, especially on PVC-additives:
Chlorophiles@ping.be