10/05/2005 Most of us
have heard of "acid rain" and even
"Purple rain", but what about "Non-stick"
rain? That is the intriguing discovery made
by scientists in Canada, who have found a
long lasting chemical called PFOS, used to
make "non-stick coatings", in rainwater
falling on Winnipeg....
Scientists have discovered that rainwater
falling on the city of Winnipeg in Central
Canada is contaminated by the "non-stick"
chemical PFOS (perfluorooctane sulphonate)
as well as other chemicals (called PFCAs,
or perfluorocarboxylic acids) belonging to
the group of "perfluorinated" chemicals.
According to research from the local Department
of Fisheries, perfluorooactane sulfonate (PFOS)
was found in rainwater at concentrations of
0.59ng to the litre.
PFOS and PFCAs have a myriad of uses in consumer
and industrial products, where they are used
as refrigerants, agrochemicals, chemical catalysts
and surfactants. PFOS is better known for
being used to make non-stick pans, grease
proof pizza boxes and (ironically) rain-proof
coats. They are stable and do not break down
easily in the environment.
Unfortunately, it is the same qualities that
make then attractive for consumer use, that
make them potentially harmful for people and
wildlife. Their chemical stability means that
they are gradually building up in the atmosphere
and in the environment.
As Dr Gregg Tomy, from the Freshwater Institute
and the University of Manitoba, who carried
out the research, explained, "PFOS is
pretty resistant to degradation and may persist
even after treatment at our local water treatment
plants". Obviously, this could mean that
the city’s drinking water is also polluted
with PFOS.
So just how harmful is PFOS? According to
the OECD’s assessment of its hazards, it is
‘persistent, bioaccumulative and toxic to
mammals. It has a half-life of 100 days in
rats, 200 days in monkeys, and years in humans’.
In monkeys it has been found to cause liver
damage, pancreatic damage, lung damage, decreased
thyroid hormone levels and, in some cases,
death.
Rainwater polluted in Europe
Unfortunately, this is not the only evidence
of harmful chemicals finding their way in
rainwater. In Europe, TNO, the Dutch research
establishment analysed samples of rainwater
taken from 50 different sites in Belgium,
Germany and the Netherlands.
The highest concentrations of chemicals TNO
found in the rainwater were phthalate plasticisers
- at one location there were concentrations
of up to 100,000 nanogrammes per litre (ng/l).
Another chemical, bisphenol-A was found in
rainwater collected at one site in concentrations
of up to 352 ng/l. Both these chemicals are
endocrine disruptors – known to be able to
interfere with the body’s reproductive functions.
The chemical alkylphenol was found in rainwater
from almost all locations. At one collection
point it was concentrated as high as 924 ng/l,
which is almost three times the safety level
in freshwater set by an EU risk assessment
for one type of alkylphenol called nonylphenol
(330ng/l).
Contamination – will go far
Neither the research in Winnipeg, nor at
the sites in Europe found any obvious source
of the chemicals. The presence of chemicals
was so widespread in the European study that
the contamination levels seem to reflect background
levels in the atmosphere.
Worldwide, recent measurements in the troposphere
(the atmosphere just above the earth’s surface
where most of the ‘weather’ originates) demonstrate
that chemicals are escaping from the products
in which they were incorporated, travelling
huge distances, and are then precipitated
from the atmosphere by oxidation and falling
as rain.
This point was also made by Mark Loewen,
from the Freshwater Institute and University
of Manitoba, who worked on the Winnipeg study.
"It wasn’t possible to pinpoint any specific
source of pollution - both local and remote
sources could very well be contributing to
the presence of these compounds in the atmosphere,
" he said.
As Joan Baez and Marianne Faithfull once
sang "What have they done to the rain?"
