| |
|
|
 |
|
Advisory Committee on Health Effects of Endocrine Disruptors
The Supplement II to the Intermediary Report
1.4.2.4 |
| |
contents
Detailed contents
<< prev
next >> |
| |
- Case control studies within cohorts with biological samples
preserved
Since a clinical test in the random allocation design on
chemicals such as organochlorines is impossible on ethical
ground, the best evidence of health effects of chemical
substances should be obtained by a case-control study within a
cohort in which biological samples for prospective study are
preserved. Determination of cancer or endometriosis incidence in
a cohort permits verification of association of a plurality of
diseases with chemical substances. It is thus possible, in
principle, to obtain data for checking if higher chemical
exposure means higher susceptibility to relevant diseases,
although some problems remain to be solved, for example to what
extent concentrations in serum or urine reflect chemical
exposure levels, or if the instruments available have enough
sensitivity and precision for detecting relevant species in the
preserved samples.
Among ongoing large-scale cohort studies in Japan, the Japan
Collaborative Cohort Study for Evaluation of Cancer Risk ("JACC
Study") conducted by a study group in the Ministry of Education,
Culture, Sports, Science and Technology, and the Japan Public
Health Center-Based Prospective Study ("JPHC Study") conducted
by a study group in the Ministry of Health, Labor and Welfare
preserve blood samples. Both have accumulated cancer data which
can provide basic information for studies on carcinogenicity of
chemicals. Indeed, the Health and Labor Sciences Research Grants
(Studies on Chemical Risks) support an analysis of case-control
study data on breast cancer using preserved plasma samples.
However, the quantity of preserved blood is not sufficient for
determination of chemicals, and most of the samples were
collected around 1990. It is desirable for new large-scale
cohort studies designed for investigation of chemical risks to
be implemented in future.
- Cohort studies on pregnant women and infants; case-control
studies on genetic abnormalities
Whereas several studies report association of breast milk dioxin
levels with thyroid functions or low cognitive performance and
nerve system disorder in infants born from mothers who consumed
PCB-contaminated fish, effects and mechanism of action of
background-level chemicals to which ordinary people are exposed
are poorly understood. The extent and duration of effects on
nerve development is practically unknown, nor association with
behavioral problems (such as AD/HD), nor with sex
differentiation disorders. Decrease of CD8-positive cells in
infant peripheral blood due to mother's intake of dioxin
suggests effects of the chemical on the immune system, but
association with immune system disorders in the infancy, such as
atopic dermatitis or asthma, remains unclear.
|
|
contents
Detailed contents
<< prev
next >> |
|
|
|
