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What exactly IS green chemistry?

By Beverley Thorpe

On July 10th CBC News released an exposé entitled: Some ‘green’ detergents still contain chemicals. The title of this article underscores all the confusion about how the public views chemicals and how we are now supposedly defining ‘green’ chemicals. The title is so blatantly misleading that I was surprised to read it. In reality ALL products contain chemicals, the human body contains chemicals, all materials on this earth contain chemicals. To imply that plant ingredients are not chemicals is a basic and unscientific misrepresentation and also a mischaracterization of what is green chemistry. So let’s review what green chemistry means.

Green chemistry is the design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances. The term came to light with the publication of a small book entitled, Green Chemistry: Theory and Practice written in 1998. In it, two US chemists, Dr John Warner and Dr Paul Anastas,outlined their Twelve Principles of Green Chemistry to demonstrate how chemical production could respect human health and the environment while also being efficient and profitable.

Many of the principles are common sense, even to a non-chemist, such as designing a molecule to be inherently safer or generate less waste in its synthesis. Why is this considered a radical approach? Because currently chemicals are typically created with the expectation that any chemical hazard can somehow be controlled or managed by establishing “safe” concentrations and exposure limits. Green chemistry aims to eliminate hazards right at the design stage. To do this a chemist must possess basic knowledge about toxicology and ecological impacts. The tragedy of our current educational system is that the chemistry curriculum does not require the study of biological sciences. This results in graduate chemists having no or little awareness about the impacts on human health and the environment of the new materials they create in the lab. Sadly, to this day, this is the norm rather than the exception. Green chemistry is considered a ‘supplemental or non compulsory’ additional course, not a mainstream approach to chemicals design.

Other Principles of Green Chemistry refer to the use of renewable feedstocks. This is where readers might be confused with the assertion that ‘plant based’ chemicals are somehow safer than petroleum based chemicals. Today’s chemical industry relies almost entirely on non-renewable petroleum as the primary building block to create chemicals. This type of chemical production is typically very energy intensive, inefficient, and toxic — and results in significant energy use, as well as generation of hazardous waste. The use of renewable materials including the use of agricultural waste or biomass can, in general, be considered less hazardous in comparison to petroleum based chemicals. However the provenance of the feedstock is important. Recently the use of palm oil has come under intense scrutiny due to its association with tropical deforestation. The type of agricultural system is important to know. Was the feedstock grown with genetically engineered crops or heavy use of toxic chemicals? Is it a food source or a non-food source of plant material? In addition it is important to also realize that it is still possible to design highly hazardous chemical formulas using bio-based feedstocks.

For example, the Solvay company in Brazil plans to make ‘Green PVC’ commonly known as vinyl, using a sugarcane based ethanol feedstock. PVC (polyvinyl chloride) is one of the most toxic plastics made. Its chlorine content generates highly toxic dioxins in the production of the monomer and the presence of chlorine in the polymer leads to the formation of chlorinated dioxins when PVC is burned. Dioxin is a well known carcinogen and has been termed the most toxic molecule ever synthesized. It is also one of the twelve POPs (persistent organic pollutants) defined by the International Stockholm Convention as a priority global pollutant targeted for phase out because of its ability to be transported and persist throughout the globe, even as far as the Arctic. Because PVC on its own is an unstable material, it requires the further addition of hundreds of chemical additives to achieve its functional characteristics, such as plasticizers to make the polymer soft, or stabilizers and hardeners to make PVC rigid. Many phthalates (tha-lates) or softeners, are known to cause hormone disruption in animal studies and this resulted in a ban on phthalates in children’s toys. Now the PVC industry is replacing certain phthalates with safer chemicals, some of which may in fact be plant based. However the substitution of one hazardous ingredient with a safer plant based formula does not make the product itself safer – or at least not when one considers the life cycle of that material. Regardless of how many plant sourced substitute ingredients the vinyl industry publicizes, the inherently hazardous nature of PVC as a chlorinated plastic remains. And it will continue to present an increasing source of global dioxin generation. One has only to look at the expanding PVC industry in Asia to realize that our global health is linked to global production systems.

The CBC News survey of detergents mentioned the Design for Environment (DfE) program of the US Environmental Protection Agency. This program requires suppliers to have all their chemicals (bio-based or petroleum based) screened against a set of criteria that measures a chemical’s impact on human health, its inherent toxicity, and ability to persist in the environment or bio-accumulate in concentration up the food chain. The criteria go much further than simply assessing the number of plant based ingredients in the product. Of course claims that a product is ‘naturally sourced’ only to discover that 30 percent of its ingredients are petroleum based are clearly misleading. But we need to understand what impacts these chemicals have; not just where they were sourced.

Responsible manufacturers know and disclose all ingredients in their products and commit to continuous improvement by phasing out inherently hazardous chemicals and replacing them with safer substitutes. New tools such as the Green Screen for Safer Chemicals developed by Clean Production Action are helping companies to achieve this move to safer substitutes. The Green Screen assesses chemicals based on a list of 17 criteria (much like the DfE set of criteria) but it goes further than the DfE program by providing four main benchmarks for companies to chart their progress to safe chemistry. HP is now the global leader in using the Green Screen to choose safer substitutes to PVC cables and hazardous flame retardant chemicals. Other major corporations in the electronics, auto and outdoor clothing industry sectors are now screening their chemicals against the Green Screen tool because the method is scientifically rigorous and transparent. This is now an important tool in the green chemistry toolbox and although it does not differentiate a chemical based on its original feedstock, it does assign a score based on its inherent hazard. And that is why green chemistry is such an elegant, complicated concept:–it encompasses all of the Twelve Principles of Green Chemistry. The challenge is now set for chemists to design new chemicals based on these Principles and for companies to demand their chemical suppliers produce inherently safer chemicals.

For more information visit the green chemicals section at: www.cleanproduction.org


 
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