When the Canadian
Environmental Law Association (CELA) set its sights on two widely used
antimicrobial agents last year, the organization wanted the results to have a
more profound impact than a typical product warning. Such warnings may be
steeped in scientific research, but that does not mean they will get a fair
public hearing — or any kind of hearing at all. In fact, it is all too easy to
imagine an audience grown numb to such news, having been warned many times
about many different chemicals posing some kind of threat to our personal
health or the health of the environment. Yet another outcry can simply be drowned
out by sports scores or celebrity scandals, especially if the chemical critique
is dominated by technical information that appears to be accessible only to an
expert elite.
CELA therefore teamed
up with the United States-based Clean Production Action (CPA), a multi-national
network of environmental activists that has been tackling this communications
challenge for more than a decade. CPA has replaced turgid collections of charts
and graphs with a much tidier means of expressing the problems that might be
associated with particular agents. This approach goes by the name GreenScreen
for Safer Chemicals (GreenScreen), a methodology that established four major
benchmarks for ranking the relative hazard or toxicity of any given chemical
expressed in common sense terms such as “Avoid — Chemical of High Concern” or
“Use but Search for Safer Substitutes.” These categories build on the 12
Principles of Green Chemistry and the US Environmental Protection Agency’s
Design for the Environment (DfE) program. It also draws on the Globally
Harmonized System of Classification and Labelling, a worldwide initiative to
promote standard criteria for classifying chemicals according to their health,
physical and environmental hazards.
DfE features an
alternative assessments initiative, which simultaneously evaluates a number of
different chemicals that might be used by any given industry for a particular
application. In this way, if research reveals that some of those agents are
less safe than others, companies have different options to weigh, rather than
merely being told that one of their major process inputs should be banned.
GreenScreen builds on this desire to provide a broader suite of background data
in order to help chemical users make what could be difficult decisions. “It’s
about a journey,” says Beverley Thorpe, the Toronto-based co-director of CPA.
“It’s about moving off chemicals of high concern to progressively safer ones.”
A GreenScreen
assessment of the common antimicrobial triclosan established that its impact
was generally minimal — except it produced dioxin in waterways.
Thorpe was especially
intrigued by the findings of CELA’s recent efforts, which began with triclosan,
a patented chlorinated aromatic compound that eliminates microscopic organisms
and began its commercial life as a hospital cleaning agent in the 1970s. More
recently the manufacturers have been using triclosan to introduce a novel
germ-fighting potential to consumer products such as soaps, toothpaste, shower
curtains, kitchen cutting boards and even toys. GreenScreen drew together the
existing data on triclosan and assessed it according to 18 separate categories
dealing with human health and environmental effects. These categories include
qualities such as carcinogenicity, endocrine activity, neurotoxicity,
bioaccumulation, and flammability. While the chemical’s impact was minimal in
some of these areas, it was extreme in others. For example, when flushed into
waterways, triclosan can react with chlorine and sunlight to produce secondary
products that may include dioxins, a particularly toxic group of
chemicals.
“Just 10 years
back we thought that concentrations in the microgram per litre/parts per
billion range were essentially inconsequential,” says Rolf Halden, director of
the Center for Environmental Security at Arizona State University’s Biodesign
Institute. “Now we find that these chemicals that mimic hormones can be
effective at even lower concentrations, in the parts per trillion range.”
Halden was part of a panel CELA assembled in 2014 to present the GreenScreen
findings for triclosan as well as triclocarban, which is a chemically similar
antimicrobial. At first glance, triclocarban might seem like a practical
substitute and its GreenScreen assessment does make it only marginally more
attractive. However, while offering a minimal impact in more categories than
triclosan does, triclocarban demonstrates even more serious toxicity to
organisms in water.
While triclosan is
coming under growing scrutiny amongst regulators and will be banned in the
state of Minnesota starting in 2017, triclocarban has yet to encounter similar
restrictions. That might make it more attractive as a substitute, but Thorpe
suggests that the GreenScreen results urge caution, since its properties could
well lead to similar regulatory pressure. “A lot of companies use the
GreenScreen to mitigate their business risks,” she says. “Any substitute for
triclosan has to go through a hazard-based alternative assessment, so that
we’re not simply telling industry to drop triclosan and pick up triclocarban
because it’s not regulated. You don’t want to be a company that moves to a
substitute, only to find out three years later you just invested $30 million in
an alternative that’s now going to be regulated.”
Thorpe explains that GreenScreen was created to serve as just such a forward-looking decision-support tool. It emerged in 2006 as part of a major DfE review of brominated flame retardants that were being used inside of furniture and electronic appliances. Makers of these goods have been treating their polyurethane foams with pentabromodiphenyl ether, which had been demonstrated to build up within the human body and therefore was scheduled for elimination under the Stockholm Convention on Persistent Organic Pollutants. Industrial representatives were lobbying to replace it with a chemical cousin — decabromodiphenyl ether — but a GreenScreen assessment highlighted toxic products emitted when this agent degrades.
On the surface, the
anti-microbial triclocarban may seem like a good alternative to triclosan.
However, its GreenScreen assessment demonstrates it is even more toxic in
water.
Other candidates
faired little better, but resorcinol bis(diphenyl phosphate) (RDP), an
oligomeric phosphate ester, eventually surfaced as the best choice. This choice
had specific regulatory implications, as the state of Maine was eager to ban
decabromodiphenyl ether, but regulators did not want to do so until they could
be sure there was a safer feasible alternative on the market. GreenScreen
offered them the assurance to proceed with the necessary legislation.
Soon after its
launch, GreenScreen’s methodology was adopted by several major manufacturers
seeking to eliminate hazardous, highly regulated chemicals from their
production chains. Electronics giant Hewlett-Packard led the way with a project
to find a substitute for polyvinyl chloride as a casing for the many different
power cords that accompany the firm’s products. This material is made with
plasticizers such as phthalates and lead to improve strength and flexibility.
However, questions continue to be raised about the health effects of these
inputs to increasingly common household appliances. “It was crucial that
Hewlett-Packard rely on some sort of method that would be scientifically
rigorous, that would enable them to be ahead of the game on impending
regulations, that would be hazard-based and would be easy for their suppliers
to understand and reformulate,” says Thorpe. By the time the company had
completed its assessment, some 30 different options had been tested. Most were
rejected, but several proved to be acceptable, giving HP some choice in the matter.
For Lauren Heine, a
US-based co-director of CPA, HP’s experience encapsulates the virtue of
GreenScreen’s ability to make positive as well as negative recommendations.
“There’s a long history of people saying, ‘you shouldn’t use this and you
shouldn’t use that,’ ” she notes, adding that when chemicals are rejected and
no obvious alternative is offered, users may simply try to tweak its formula to
reinstate its use. In order to avoid this, GreenScreen steps away from the
well-established approach to chemical safety, where discussions revolve around
the concept of risk. Instead, assessments are based on the concept of hazard,
which often leaves the makers of chemicals less comfortable. “It’s fairly
intuitive to a toxicologist,” says Heine, who suggests that an emphasis on
hazard makes it easier to describe how an agent behaves, rather than how well
we use it. “It’s more science and less opinion.”
Heine points to an
agent such as propane, which scores poorly with GreenScreen because of its high
flammability but remains popular in everything from manufacturing to backyard
barbecues because the public accepts what is regarded as a manageable risk. In
contrast, agents that could cause cancer will score just as poorly and evoke a
great deal of emotion among users, who may fear this risk cannot be controlled.
Nevertheless, the hazard may be less than that associated with
flammability.
Companies responsible
for chemicals that populate our homes and workplaces therefore prefer risk
assessments, which enable them to make claims that they are managing risks
well. According to Heine, information about hazards is more objective and in
many ways more practical. “Unless you have a way of comparing and contrasting
chemicals and choosing safer options, then how are people supposed to make
better decisions?”
Major corporate
users, which include Staples and Walmart, among others, are demonstrating their
own preference for GreenScreen’s hazard-based approach. Heine acknowledges that
the secrecy around proprietary formulations holds back some participants, who
prefer not to share everything about the agents they employ in their business.
Even so, CPA has a Web-mounted database of GreenScreen-reviewed agents that
continues to grow. Moreover, the methodology is universally available and
down-loadable in an open-source format, so that governments, scientific
agencies and private corporations have all developed their own variation on the
theme. Nor are the architects of GreenScreen particularly worried about seeing
their product reinvented elsewhere; they voice their contentment at seeing a
good idea spread. “I may be an optimist,” says Heine, “but I do think that if
people have the tools, they’ll use them and make better choices.
Design
for the Environment
Created in the early
1990s by the United States Environmental Protection Agency, Design for the
Environment (DfE) disseminates information about safer commercial products and
best environmental practices. The program emphasizes a reduction in how goods
and services affect human health or the environment, examining these effects
from a life cycle perspective. DfE has been responsible for hundreds of
businesses adopting different chemicals and alternative technologies, resulting
in safer consumer, industrial and institutional products. More than 2,500 of
these products have been permitted to display a DfE logo indicating this
status, so that consumers and industrial purchasers can make informed choices.
The
12 Principles of Green Chemistry
Developed by American
chemists Paul Anastas and John Warner in the 1990s, this list defines the
nature of green chemical use and manufacture.
- Prevention: It is better to prevent waste than to treat or clean up waste after it has been created.
- Atom Economy: Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final product.
- Less Hazardous Chemical Syntheses: Wherever practicable, synthetic methods should be designed to use and generate substances that possess little or no toxicity to human health and the environment.
- Designing Safer Chemicals: Chemical products should be designed to affect their desired function while minimizing their toxicity.
- Safer Solvents and Auxiliaries: The use of auxiliary substances (e.g., solvents, separation agents, etc.) should be made unnecessary wherever possible and innocuous when used.
- Design for Energy Efficiency: Energy requirements of chemical processes should be recognized for their environmental and economic impacts and should be minimized. If possible, synthetic methods should be conducted at ambient temperature and pressure.
- Use of Renewable Feedstocks: A raw material or feedstock should be renewable rather than depleting whenever technically and economically practicable.
- Reduce Derivatives: Unnecessary derivatization (use of blocking groups, protection deprotection, temporary modification of physical/chemical processes) should be minimized or avoided if possible.
- Catalysis: Catalytic reagents (as selective as possible) are superior to stoichiometric reagents.
- Design for Degradation: Chemical products should be designed so that at the end of their function they break down into innocuous degradation products and do not persist in the environment.
- Real-time analysis for Pollution Prevention: Analytical methodologies need to be further developed to allow for real-time, in-process monitoring and control prior to the formation of hazardous substances.
- Inherently Safer Chemistry for Accident Prevention: Substances and the form of a substance used in a chemical process should be chosen to minimize the potential for chemical accidents, including releases, explosions and fires.