Da uno studio statunitense emerge una rassegna dei principali gruppi di sostanze chimiche potenzialmente cancerogene.
Gas di scarico dei veicoli, fumo di sigaretta,inquinamento dell’aria, cibi troppo cotti, prodotti chimici e certi farmaci.
Lo studio, pubblicato su Environmental Health Perspectives, è stato condotto dai ricercatori del Silent Spring Institute e dalla Harvard School of Public Health.
I ricercatori hanno comparato l’evidenza scientifica dei risultati con i
dati sull’uomo riportati nelle principali revue, compilando una
presentazione contenente le informazioni dei relativi studi di cohorte.
Nello studio si legge che i risultati degli studi sul cancro al seno
dell’uomo sono generalmente consistenti con i dosaggi biologici sui
roditori, anche se pochi agenti sono stati studiati nell'uomo.
La ricerca evidenzia 17 categorie di sostanze potenzialmente più a rischio rispetto a questa malattia.
Tra gli obiettivi prioritari, la riduzione dell’esposizione a tali
agenti, presenti soprattutto nei gas di scarico delle automobili, nella
benzina, nell’aria inquinata, nel fumo di sigaretta, ma anche in alcuni
cibi troppo cotti (fritti ad alte temperature o carbonizzati), tinture,
mobili trattati (con PFOA), in certi casi in qualche farmaco (ad es.
‘distruttori endocrini’), particolari materiali (ad es. ritardanti di
fiamma) e in certi solventi chimici (alogenati) e in altre sostanze
indicate nello studio (vedere l'allegato).
I 17 gruppi di sostanze chimiche dannose:
• 1,3 butadiene: l’esposizione a questa sostanza avviene principalmente
attraverso l’inalazione del fumo di sigaretta, il gas di scarico delle
automobili e vapori della benzina.
• Acrilamide: l’esposizione
include il fumo di tabacco e particolari cibi ricchi di amido e cotti in
un certo modo (patatine fritte ad alta temperatura); si ritiene inoltre
che sia presente in alcuni materiali (malta liquida, adesivi, gel al
poliacrilamide utilizzati in molti prodotti di consumo – ad esempio si
possono trovare nei pannolini e nell’acqua potabile trattata).
•
Ammine aromatiche: in generale, nelle ammine aromatiche l’azoto è legato
al benzene o ad un altro anello aromatico. Sono state individuate 15
ammine aromatiche che causano tumori nei dosaggi biologici dei tumori di
roditore. TDA e TDI: in generale, tali sostanze vengono utilizzate per
la sintesi industriale di poliuretano, pesticidi, tinture ed altri
prodotti.
• Altre ammine aromatiche (benzidina e anilina): alcune
tinture possono derivare dall’uso di questi composti, che possono essere
utilizzati anche nell’industria tessile, vernici, inchiostri per
stampanti, carta, farmaci; reagenti e colorazioni biologiche in
laboratorio, nell’industria del cibo; laser, stampanti ink-jet,
cristalli liquidi, schermi, dispositivi elettro-ottici.
• Benzene:
oltre ai vapori di benzina, si trova nel fumo di tabacco, ma anche nei
gas di scarico delle automobili e in altri tipi di inquinamento urbano e
industriale. E poi, nei composti per rimuovere gli adesivi, nelle
vernici, nei sigillanti, rifinitori, combustibili ed oli dei motori.
• Solventi organici alogenati: cloruro di metilene e altri nove
solventi organici. Utilizzati soprattutto in passato, si possono trovare
in alcuni prodotti (lavaggio a secco, propellente spray per capelli,
fumiganti, trasformazione dei prodotti alimentari, additivi della
benzina,vernice e smacchiatori).
• Ossido di etilene e propilene: è
un gas che può essere utilizzato per sterilizzare attrezzature mediche,
cibo e spezie, vestiti e strumenti musicali; ma anche nelle vernici,
fumo di tabacco e gas di scarico dei veicoli.
• Ritardanti di fiamma
e metaboliti: possono essere presenti nella resina poliestere, polimeri
plastici e schiume di poliuretano rigide.
• Ammine eterocicliche:
composti che per definizione contengono almeno un anello eterociclico,
presenti soprattutto nel fumo di tabacco e nella carne cucinata ad alte
temperature.
• Ormoni endogeni o farmaceutici e ‘distruttori
endocrini’: estrogeni, progesterone e l’ormone DES e con effetto minore
sui roditori le sostanze ECDs.
• MX:è uno dei prodotti che possono essere utilizzati per la disinfezione dell’acqua potabile.
• Nitro- PAHs: si trovano nel gas di scarico del diesel
• Ocratossina A: la principale fonte di esposizione è legata ad
alimenti contaminati tra cui grano, carne di maiale e noci contaminati.
• PAHs:fumo di tabacco, aria inquinata e cibi carbonizzati
• Acido perfluoroottanoico (PFOA): l’PFOA insieme ad altri composti
perfluorinati (PFC) possono essere utilizzati per rivestimenti
resistenti e antiaderenti su tappeti, mobili, vestiti e stoviglie, ma
anche cosmetici, lubrificanti, vernici e presidi anti-incendio.
•
Farmaci non ormonali:Questi includono quattro agenti chemioterapici, due
farmaci veterinari eventualmente presenti negli alimenti, il diuretico
furosemide e la griseofulvina antifungino, vari agenti anti-infettivi, e
due farmaci non più molto utilizzati, la fenacetina, un antidolorifico
da banco, e il farmaco anti-ipertensivo reserpina.
• Stirene:
esposizione in microgrammi al giorno, legata alla presenza di fumo di
sigaretta, componenti dell’aria all’interno dell’abitazione e quantità
di cibo che sono state in contatto con polistirene.
ENGLISH VERSION :
Silent Spring Institute’s perspective on the report’s top take-home points related to environmental chemicals
The Institute of Medicine report on breast cancer and the environment
is a clear statement to breast cancer doctors, many of them gathered in
San Antonio where the report was released, that a cascade of scientific
evidence shows that environmental chemicals have biological activity
that plausibly links them to breast cancer risk. That’s a significant
step, because for years, medical experts have dismissed questions about
environmental chemicals and breast cancer and ridiculed concerns about
consumer products - from deodorants to plastics - as “myths,” saying
that there’s no evidence that exposures cause breast cancer. The “no
evidence” messages ignored studies by Silent Spring Institute and others
that show hundreds of chemicals in consumer products and pollution
cause breast tumors in animals, mimic estrogen (a known breast cancer
risk factor), and stunt breast development. Now, the IOM recognizes
that we must pay attention to this full range of research, including
laboratory experimental studies, acknowledging that evidence from human
studies is often not attainable.
Acknowledging that
definitive human evidence of breast cancer links is unattainable for
many chemicals we are exposed to across a lifetime, the IOM recommends
better methods for experimental testing of chemicals specifically for
effects relevant to breast cancer. What’s implied is that experimental
studies that show a chemical might plausibly increase breast cancer risk
are a reasonable basis for action to reduce exposure, since human data
are difficult or impossible to obtain. In the context of U.S. breast
cancer institutions focused on mammography and treatment, the
recommendation for chemicals testing is a significant positive step for
prevention. The President’s Cancer Panel report on the environment was
the first major statement that safety testing of consumer product
chemicals should be part of the nation’s cancer response, and this IOM
report continues that discussion specifically for breast cancer. The
President’s Cancer Panel and IOM both extend Silent Spring’s earlier
analyses published in Cancer and Environmental Health Perspectives.
The report recommends that we “limit or eliminate workplace,
consumer, and environmental exposures to chemicals that are plausible
contributors to breast cancer risk while considering risks of
substitutes.” That sounds like common sense, but it represents a
significant departure from the prevailing skepticism in the medical
community about environmental chemicals and breast cancer prevention.
Plausible contributors to breast cancer include chemicals that are
mammary gland carcinogens in animals, affect hormones, or influence
breast development during a critical exposure periods.
The IOM
concludes that smoking increases breast cancer risk and passive smoke
should be avoided. Yes, we already know that smoking is bad, but
acknowledging its relevance to breast cancer adds weight to evidence
about other environmental chemicals, including dozens in tobacco smoke
that also have other common exposure sources, such as auto exhaust and
air pollution.
The report calls out three specific chemicals
-- ethylene oxide, benzene, and 1,3-butadiene – saying both animal and
human studies indicate breast cancer risks. As far as we know, this is
the first statement by an authoritative medical group linking any
specific environmental chemical to breast cancer. Primary exposures to
benzene and 1,3-butadiene are from gasoline, air pollution, and auto
exhaust. Ethylene oxide is a sterilant used, for example, in medical
settings and food sanitation. All three chemicals are in tobacco smoke.
Silent Spring Institute previously highlighted these chemicals (among a
few others) in our 2007 review of environmental factors and breast
cancer, and their targeting by the IOM committee extends this previous
work. We hope the IOM report will lead to greater worker protections,
including access to mammography and breast cancer treatment, and make it
easier for researchers who want to study these exposures to get funded.
If the report’s research recommendations related to environmental
chemicals are implemented, we expect the list of chemicals with similar
evidence will grow longer.
Our own list of chemicals with both
human and animal evidence of breast cancer risk is longer than the IOM’s
and includes polychlorinated biphenyls (PCBs), polycyclic aromatic
hydrocarbons (PAHs), and common organic solvents. Current exposures to
PCBs, which are banned, come primarily from consumption of certain fish,
and from air in older buildings, including schools and homes where they
were used in floor finishes and caulks in the 1950s and 1960s. PAHs
are ubiquitous air pollutants and found in tobacco smoke and grilled
food. Common organic solvents such as methylene chloride are used in
glues, spot removers, dry cleaning, and other consumer products; they
are common drinking water contaminants and many people are exposed in
the workplace. The possibility that many organic solvents increase risk
deserves particular attention, because alcohol, a recognized breast
cancer risk factor, and benzene, highlighted by the IOM, fall into this
chemical class. The evidence so far suggests that higher risks for
PCBs, PAHs, and solvents may be limited to genetically susceptible
people or those exposed at an early age, but breast cancer is so common
that these subgroups of the population are large.
It’s also an
oversight that the IOM document does not mention an important study by
Kaiser Permanente on breast cancer risk among women taking
pharmaceuticals that cause mammary gland tumors in animal studies. This
study showed increased breast cancer risk from griseofulvin (an
antifungal) in particular and also from furosemide and metronidazole
(Friedman et al. 2008). While it is an important step that the IOM
recommendations (#10, 11) suggest better pre- and post-market testing of
hormonally-active pharmaceuticals for breast cancer risk, it would be
better to extend the recommended safety testing to include other
pharmaceuticals, especially those that cause breast tumors in animals.
The IOM highlights chemicals with hormonal activity, including
perfluorinated compounds, bisphenol A, and the pesticide atrazine, as
priorities for research, because the evidence of plausible biological
links to breast cancer is “provocative” but difficult to interpret so
far. Their recommendation for research to evaluate “the persistence and
consequences for mammary carcinogenicity of abnormal mammary gland
development and related intermediate outcomes observed in some
toxicological testing” is drawn from Silent Spring Institute’s recent
publications that call for toxicological testing to assess the effects
of chemicals on breast development and cancer susceptibility.
What’s needed now is a clear statement by cancer heavyweights like
Komen, the sponsor of the IOM report, saying the evidence of links
between chemicals and breast cancer is mounting, and we’re past the
point where we don’t know enough to act. We desperately need breast
cancer organizations to work for chemical safety testing for effects on
breast cancer, reform of the Toxic Substances Control Act, and pollution
policies that recognize breast cancer among the risks. We also need
them to invest in the IOM’s prevention research agenda on par with
investments in improved screening and treatment. The report includes
ambitious research recommendations to improve ability to test chemicals,
interpret results, and study exposures in humans, but these are all
expensive and there are currently few governmental or breast cancer
organizations funding this work, aside from the forward-looking
California Breast Cancer Research Program. The $5 - 7M in new prevention
grants announced by Komen is not enough.
We read the IOM
report with particular interest, because Silent Spring Institute led a
team that reviewed the scientific evidence on environmental factors and
breast cancer in a 2007 supplement to the American Cancer Society’s
peer-reviewed journal, Cancer. That project, like the IOM report, was
funded by Komen for the Cure. The new report builds on our earlier
Cancer papers and our more recent studies. We hope that by highlighting
the increasing evidence of plausible links, the IOM’s work will lead to
a new national focus on environmental chemicals as an important focus
for breast cancer prevention.
Breast cancer is still a killer, the
leading cause of death for women in mid life, and an enormous source of
suffering for the 230,000 US women diagnosed each year. Nearly everyone
knows someone close who has been through debilitating treatment,
fueling an urgent cry for insights into prevention and evidence about
what’s safe. This report provides evidence for action and a crucial
agenda for research to change the legacy of breast cancer for our
daughters’ generation. Because breast cancer is so common and the
suspect chemicals so widespread, the nationwide benefit of finding and
eliminating the risks would be large, even if the incremental risk to
any one woman is small. |
