The Science of Emerging Risks Part Two

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16 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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Lovells LLP

Endocrine Disrupters


Industries which may be affected by
endocrine disrupters



Chemicals


Plastics


Agrochemicals


Water companies


Farming


Food


Cosmetics



Endocrine system



Hypothalamus


Pituitary


Thyroid


Pancreas


Adrenal glands


Ovaries


Testes


Hormone action and receptor binding

http://www.emcom.ca/primer/hormones.shtml

Hormone

Target Cell

Receptor

Hormone feedback pathways and
homeostasis

http://www.who.int/ipcs/publications/en/ch3.pdf

Example
-

control of spermatogenesis and
testosterone secretion

Definition of endocrine disrupter



An endocrine disruptor is an exogenous substance or
mixture that alters function(s) of the endocrine system
and consequently causes adverse health effects in an
intact organism, or its progeny, or (sub)populations.



A potential endocrine disruptor is an exogenous
substance or mixture that possesses properties that
might be expected to lead to endocrine disruption in an
intact organism, or its progeny, or (sub)populations.










[http://www.who.int/ipcs/publications/en/ch1.pdf]





Sites of endocrine disruption

Hormone synthesis

Hormone
transport

Hormone binding

Hormone
metabolism and
excretion

Hormone

Target
Cell

Receptor

Mechanism of endocrine disruption


EDCs can bind to a receptor and trigger the usual
response.



EDCs can bind to the receptor and not trigger a
response but cause a blockage such that the appropriate
hormone cannot bind



Can interfere with the production, transportation,
metabolism and excretion of hormones



Many EDCs are capable of multiple, sometimes
opposing, actions in different tissues


Effects of endocrine disruption
-

TBT


http://www.credocluster.info/images/imposex.gif

http://www.medinavalleycentre.org.uk/im
ages/fs_marine_biology_dogwhelk.jpg

TBT


Survey of the dogwhelk showed a high degree of
imposex



Observed to be in areas close to shipping activity



Tissues of the dogwhelk were analysed for several
compounds and showed high levels of tin



Experiments conducted using TBT which demonstrated
a causative link



Mechanism by which the disruption is caused is still
unclear


Effects of endocrine disruption
-

DES









Given to pregnant women
who were at risk of
miscarriage or premature
birth (1938
-
1971)


Synthetic estrogen



DES

http://www.cdc.gov/des/

Examples of established endocrine
disrupters



Dioxins




PCBs




DDT

Examples of chemicals which are potential
endocrine disrupters in humans



TBT


Bisphenol A


Atrazine


Phthalates


Phytoestrogens


Alkylphenols


Brominated flame retardants

Products which contain potential endocrine
disruptiers



Industrial chemicals


Pesticides


Herbicides


Plastics (phthalates)


Cosmetics (bisphenol A)


Sunscreens (4MBC & OMC)


Fire retardants (brominated compounds)


Problems associated with the management
of endocrine disrupters


Identification of potential disrupters


Multigenerational effects


Timing of exposure


Combined exposures


Multiple effects on different endocrine pathways


Persistence and cumulative effects


Appropriate and standardised tests for ED ability


Low dose effects/threshold


Dose
-
response

Attempts to identify ED chemicals


EC


Priority list of substances for further evaluation of their role in
endocrine disruption


CREDO research initiative


REACH



EPA’s Endocrine Disruptor Screening Program (EDSP)


“Draft List of Chemicals for Initial Screening” June 2007


Endocrine Disruptors Research Initiative



WHO


2002 Global Assessment of the State of the Science of
Endocrine Disruptors

Lovells LLP

EMF


EMF spectrum

Frequency/wavelength affects
properties of EM waves


Very high frequency radiation



Lots of energy


Ionising radiation


Able to easily penetrate (and damage) biological material


X
-
rays and gamma rays



Radiofrequency wavelengths (10MHz to 300GHz)



Less energy associated


Non
-
ionising radiation


Less able to penetrate biological materials


Mobile phones and microwave



Low
-

and extra
-
low frequency radiation



Low power levels


Non
-
ionising


Power lines

Risks of EMF




Ionising radiation


various adverse effects including cancer



Ultraviolet and visible radiation


various adverse effects including
skin cancer



Radiofrequency radiation


exposure at greater than ICNIRP
guideline levels can lead to thermal effects



Low frequency radiation


exposure greater than ICNIRP guideline
levels can lead to shocks and effects on the nervous system



Magnetic fields


classified by IARC as possibly a human
carcinogen on the basis of studies relating to childhood leukemia


How are electric and magnetic fields
generated

Mobile phones

http://www.hpa.org.uk/radiation/understand/information_sheets/mobi
le_telephony/background_info.htm

Guidelines for exposure to non
-
ionising
radiation set by ICNIRP



European power frequency

Mobile phone base station
frequency

Microwave
oven
frequency

Frequency

50 Hz

50 Hz

900 MHz

1.8 GHz

2.45 GHz



Electric field
(V/m)

Magnetic
field (µT)

Power
density
(W/m
2
)

Power
density
(W/m
2
)

Power
density
(W/m
2
)

Public
exposure
limits

5 000

100

4.5

9

10

Occupational
exposure
limits

10 000

500

22.5

45




ICNIRP, EMF guidelines, Health Physics 74, 494
-
522 (1998)

Examples of typical maximum exposures



Typical maximum public exposure (W/m
2
)

TV and radio
transmitters

0.1

Mobile phone base
stations

0.1

Radars

0.2

Microwave ovens

0.5

Source

Typical maximum public exposure

Electric field (V/m)

Magnetic flux density
(µT)

Natural fields

200

70 (Earth's magnetic
field)

Mains power

(in homes not close
to power lines)

100

0.2

Mains power

(beneath large power
lines)

10 000

20

Electric trains and
trams

300

50

TV and computer
screens

(at operator position)

10

0.7


Source: WHO Regional Office for Europe

IARC classification of static electric and magnetic
and extremely low
-
frequency electric fields

“Evaluation

There is limited evidence in humans for the carcinogenicity of extremely low
-
frequency magnetic fields
in relation to childhood leukaemia.


There is inadequate evidence in humans for the carcinogenicity of extremely low
-
frequency magnetic
fields in relation to all other cancers.


There is inadequate evidence in humans for the carcinogenicity of static electric or magnetic fields and
extremely low
-
frequency electric fields.


There is inadequate evidence in experimental animals for the carcinogenicity of extremely low
-
frequency magnetic fields.


No data relevant to the carcinogenicity of static electric or magnetic fields and extremely low
-
frequency
electric fields in experimental animals were available.


Overall evaluation

Extremely low
-
frequency magnetic fields are possibly carcinogenic to humans (Group 2B).


Static electric and magnetic fields and extremely low
-
frequency electric fields are not classifiable as to
their carcinogenicity to humans (Group 3).”


http://monographs.iarc.fr/ENG/Monographs/vol80/volume80.pdf

World Health Organisation Factsheet


June
2007
-

extremely low frequency fields




In 2002, IARC published a monograph classifying ELF magnetic fields as
"possibly carcinogenic to humans". This classification is used to denote an
agent for which there is limited evidence of carcinogenicity in humans and
less than sufficient evidence for carcinogenicity in experimental animals
(other examples include
coffee

and
welding fumes
). This classification was
based on pooled analyses of epidemiological studies demonstrating a
consistent pattern of a two
-
fold increase in childhood leukaemia associated
with average exposure to residential power
-
frequency magnetic field
above 0.3 to 0.4
µ
T. The Task Group concluded that additional studies
since then do not alter the status of this classification.



However, the epidemiological evidence is weakened by methodological
problems, such as potential selection bias. In addition, there are no
accepted biophysical mechanisms that would suggest that low
-
level
exposures are involved in cancer development. Thus, if there were any
effects from exposures to these low
-
level fields, it would have to be
through a biological mechanism that is as yet unknown. Additionally,
animal studies have been largely negative.
Thus, on balance, the evidence
related to childhood leukaemia is not strong enough to be considered
causal.


Research into potential effects of RF
radiation on humans



World Health Organisation
-

The International EMF
Project



REFLEX



MTHR
-

UK Mobile Telecommunications and Health
Research Programme



Interphone

Reports on EMF/RF


1999 Canadian Report Royal Society of Canada's Expert Panel's review of the potential health risks of
radiofrequency fields from wireless telecommunication devices


2000 Zmirou Report French Health General Directorate


2000 Stewart Report UK Independent Expert Group


2002 Dutch Report Health Council of the Netherlands, advisory report


2003 Swedish Report Swedish Radiation Protection Authority (SSI) First annual report from SSI's Independent
Expert Group on Electromagnetic Fields


2003 AGNIR Report NRPB's Independent Advisory Group on Non
-
Ionising Radiation Report 'Health Effects from
Radiofrequency Electromagnetic Fields'


2004 Dutch Report Health Council of the Netherlands Electromagnetic Fields Annual Update 2003


2004 Review by ICNIRP Standing Committee on Epidemiology A comprehensive review of the epidemiology of
health effects of radiofrequency exposure


2004 Swedish Report Swedish Radiation Protection Authority (SSI) Second annual report from SSI's Independent
Expert Group on Electromagnetic Fields


2005 NRPB Report W65 A Summary of Recent reports on Mobile Phones and Health (2000
-
2004)


2005 NRPB Report Documents of the NRPB
-

Mobile Phones and Health Volume 15 No.5 2004


2005 French Agency for Environmental Health Safety Opinion on Mobile Telephony


2005 Dutch Report Health Council of the Netherlands Electromagnetic Fields Annual Update 2005


2005 Swedish Report Swedish Radiation Protection Authority (SSI) Third annual report from SSI's Independent
Expert Group on Electromagnetic Fields


2007 Dutch Report Health Council of Netherlands


2007 Swedish Report Swedish Radiation Protection Authority (SSI)


2007 June Canadian Report Update report by the Royal Society of Canada's Expert Panel on Potential Health
Risks of Radiofrequency Fields from Wireless Telecommunication Devices

World Health Organisation Factsheet


May 2006
-

Base stations and wireless technologies






Considering the very low exposure levels and research results
collected to date, there is
no convincing scientific evidence that
the weak RF signals from base stations and wireless networks
cause adverse health effects
.





While no health effects are expected from exposure to RF fields
from base stations and wireless networks
, research is still being
promoted by WHO to determine whether there are any health
consequences from the higher RF exposures from mobile phones
.






The International Agency for Research on Cancer (IARC), a WHO
specialized agency, is expected to conduct a review of cancer risk
from RF fields in 2006
-
2007 and the International EMF Project will
then undertake an overall health risk assessment for RF fields in
2007
-
2008.