Issue 26 – Green Chemistry

Issue 26, May 2010 (scroll down for this month’s articles): Better living through green chemistry :: Research links pesticides to higher melanoma risk :: Possible epigenetic mechanism for harm from two chemicals :: Plus 5&5, a round-up of the best news and science from April.

Better living through green chemistry: prospects for an under-fire chemicals industry

Ibuprofen molecule

Ibuprofen provides an example of atom economy in green chemistry, in which a process wasting 60% of materials by weight was refined in the 1990s to wasting only 1%-23%

As controversy around society’s use of chemicals grows, green chemistry is getting more attention as a way of lessening the impact of chemicals on the environment and health.

In the past, how effective a chemical is at achieving its primary purpose has been far more important in determining whether it should be placed on the market than its potential for causing environmental harm, with very little systematic toxicity testing required before chemicals have been sold and used.

However, increasing amounts of independent research using modern techniques, combined with a better understanding of how chemicals interact with complex processes in the body, are pointing to an ever-increasing array of environmental and health problems linked to the use of chemical products in today’s society.

Anyone closely involved with chemicals issues will have seen how, in the last 18 months, the industry is developing the beginnings of an image problem.

The conflagration in the US around BPA, a chemical used in food can linings and polycarbonate bottles, is spreading to Europe with a newspaper campaign in the UK and a provisional ban on the substance in Denmark.

There is talk of further bans in other countries including France and a backdrop of active campaigning against BPA by environmental organisations. In general, public concern about chemical exposure is growing.

As a manufacturer of over 70,000 products and worth 2 trillion GBP (2.3 trillion EUR) annually, yet historically under-regulated, it could be argued that trouble has been waiting for the chemical industry.

New regulation such as REACH in Europe and mooted reform of the US Toxic Substances Control Act will make it harder for untested and potentially toxic products to get on or stay on the market.

Under regulatory and social pressure, some companies and researchers are turning to the relatively new discipline of green chemistry.

The stage was set for green chemistry by the US 1990 Pollution Prevention Act, which focused attention on the prevention of pollution at source rather than the treatment of pollutants after they are formed, becoming a formal goal of the US Environmental Protection Agency in 1991.

The US Green Chemistry Institute was set up in the late 1990s, and in 2000 partnered the American Chemical Society.

“Green chemistry’s fundamental tenet is pollution prevention – preventing toxic and hazardous chemical pollution at the design stage,” says Elizabeth Grossman, environmental science writer and author of Chasing Molecules, a book about the history and potential of green chemistry.

One striking example of how this principle has made it into practice is in the development of an alternative to formaldehyde-based glues in furniture.

A human carcinogen, formaldehyde has been in use in making wood composites such as plywood and fibreboard since the 1940s, creating hazards for workers and being one source for poor indoor air quality in homes and offices.

Around 2003, Professor Kaichang Li, a wood science researcher at Oregon State University, was looking at the properties of the protein which mussels use to stick themselves to rocks.

Adapting amino acids in soy protein to resemble those of mussels’ adhesive protein, Li was able to find a substitute glue for commercial application in plywood and fibreboard.

“I was amazed […] to see these small mussels attach themselves so strongly to rocks,” Li said at the time. “I didn’t know of any other type of adhesive that could work this well in water and withstand so much force.”

Formaldehyde-free, Li’s glue has reduced hazardous air pollutant emissions from Columbia Forest products (one of the commercialising parties) by 50 to 90%, protecting workers from formaldehyde fumes and preventing formaldehyde off-gassing from wood furniture in homes. In 2007, Li’s work was recognised with a US Presidential Green Chemistry Challenge award.

A second award highlights how green chemistry, in the words of Grossman, invites scientists to “step back and ask: what are we trying to do here?”.

In the case of formaldehyde the problem was a matter of finding an alternative molecule which could act as a bonding agent, but it is not always possible to replace a toxic molecule with a less toxic one.

For example, it is not obvious what sort of non-toxic chemical can be added to plastics such as PVC to make them less flammable.

Each generation of fire retardants has presented its own problems, with new research suggesting that the newest retardants, thought to be safer, may yet be altering hormone and sperm levels in men.

Grossman remarks that even if we did find a safe molecule to stop plastics catching fire, “we would still be using PVC, so there is a question as to how much progress to sustainability we would have made anyway.”

In these cases, a whole-sale reinvention of a process, such as substituting aluminium casing for PVC, may be the genuinely green solution.

Something equivalent to this is what happened when CEM Corporation, the first Presidential Green Chemistry Challenge award winner for an analytical process, looked at how protein content of food is analysed.

Normally carried out using the Kjeldahl method, devised by a Danish scientist over 130 years ago, the method is slow and uses toxic and hazardous substances.

“The process takes two to four hours, effectively digesting the food sample in high-temperature sulphuric acid with a heavy metal catalyst,” explains Michael Collins, PhD, CEO of CEM.

Collins’ company came up with a novel way of identifying proteins, developing a process by which a non-toxic water-soluble dye bonds to three protein amino acids, allowing protein samples to effectively be mashed up, filtered, and tested for protein content with simple colorimetry.

CEM estimates that testing protein content with the Kjeldahl method generates 2.5 million kilograms of hazardous waste per year, while their Sprint protein testing technology produces no hazardous waste at all.

CEM’s Sprint technology has another major advantage: it isn’t fooled by high-nitrogen compounds such as melamine or urea, used to adulterate pet food and, in a recent scandal, baby milk as a way of faking high protein content.

There is a question as to how receptive the chemicals industry is as a whole to green chemistry, but Collins believes, at least in the testing world, there is a genuine motivation towards greener rather than just more efficient processes: “Testing generates a lot of toxic waste, using organic solvents and toxic chemicals for analyses; there is a general feeling we should be greener and less detrimental to the environment.”

Although promising safer consumer products, green chemistry could have its most drastic impact at the industrial scale in developing countries, where more and more of the world’s manufacturing, and thus some of the world’s worst industrial pollution, occurs.

Two of the countries where green chemistry is being incorporated into university curricula most widely are China and India.

China is now the second-most prolific source after the US of green chemistry papers, while in India the University of Delhi requires every chemistry student to take a full year of green chemistry.

It is too early to say how far the wave of interest in green chemistry will carry chemists. However, in an industry perhaps becoming accustomed to more bad news than good, it seems there are opportunities for genuinely better, more sustainable living through chemistry.

New research links pesticides to higher melanoma risk

Pesticide spraying

New research points to pesticides as an additional risk factor to sun exposure in skin cancer.

By James Black

Scientists in the USA have identified a set of pesticides which double the chance of melanoma among agricultural workers, if repeatedly exposed.

Much of the current research on the causes of melanoma has focused on a range of factors coupled with exposure to the sun.

However, the new study, carried out by scientists at the University of Iowa, has found a direct association between pesticides and skin cancer.

Over 56,000 farm workers and their spouses, from Iowa and North Carolina in the US, took part in the study.

After asking the subjects about their exposure to some 50 chemicals, the researchers compared cancer rates, and found that those exposed to a certain group of pesticides had higher rates of cutaneous melanoma than those exposed to other chemicals.

David Coggon, Professor of Occupational and Environmental Health at the MRC Environmental Epidemiology Unit of Southampton University (UK), welcomed the study, but expressed reservations about concluding a definite link between the chemicals and instances of melanoma.

“The study is well designed,” he said, “but when so many combinations of pesticide and cancer are examined, some can be expected to show associations simply by chance. Thus, I would not put too much weight on these findings for melanoma in isolation.

“Overall, farmers in the England and Wales do not appear to have unusually high mortality from melanoma when compared with other occupations.”

However, toxicity consultant Tony Tweedale argues that regulators need to give more weight to existing literature linking certain chemicals and instances of melanoma.

He said: “Exposure to mutagens [besides sunlight] may be adding to our risk of melanoma. Pesticides especially are often applied in sunlight, and professional pesticide applicators do so constantly. Animals constantly repair mutations, but cancer often results when these repair systems are overwhelmed.”

Four of the six pesticides studied remain in regular use while two have already been banned. A further two, benomyl and ethyl-parathion, were voluntarily withdrawn by manufacturers nearly two years ago.

Epigenetic studies shed new light on mechanism for reproductive toxicity of chemicals

Mouse with bent tail

These mice are genetically identical but differences in gene methylation, an epigenetic change, has given one mouse a kinked tail.

Two new animal studies have suggested that some chemicals may affect reproductive development by interfering with how genes are turned on and off.

The first study, looking at how BPA administered to pregnant mice affected the female offspring, found that the chemical increases a gene’s responsiveness to oestrogen.

The researchers discovered that BPA was removing methyl groups from the foetus’ DNA, effectively activating the gene in question.

Methyl groups are one important epigenetic structure. Epigenetics is the study of the non-genetic mechanisms by which genes are expressed.

Changes in the epigenetic structure have been shown to cause permanent alteration in development, such as colour changes and propensity to obesity in mice.

A relatively new discovery, epigenetic mechanisms are improving understanding of how genes are expressed in the body, while giving cause for concern that chemicals could be causing health problems in humans by altering epigenetic structures.

In the second study, researchers induced testicular dysgenesis syndrome in male foetuses by exposing pregnant mice to DEHP.

The researchers found changes in DNA methylation and speculated that this epigenetic change may be one possible mechanism of DEHP-mediated toxicity.

5&5: News and science highlights from April

News

Revealed: the nasty secret in your kitchen cupboard: The Independent reports that 18 out of 20 of the most popular tinned foods in the UK are packaged in tins lined with BPA.

The Perils of Plastic – Environmental Toxins: TIME magazine with another very strong piece on how environmental chemicals affect health, focusing on exposure emanating from plastics.

Harvard’s Berwick Tapped for Health Agency: The NYT reports how Dr Donald Berwick, a pediatrician, is in line to administer the reformed US state healthcare. He says: “The best hospital bed is empty, not full. The best CT scan is the one we don’t need to take. The best doctor visit is the one we don’t need to have.”

The weight of evidence: Subtle editorial from Nature about the need for scientific reform to back up moves toward legislative reform regarding chemicals to ensure only quality science informs policy-making; the points are salient to Europe as well as the US.

FDA reviewing use of antibacterial products: The LA Times reports on how the FDA is going to look at the safety of triclosan, to see if it promotes antibiotic resistance in bacteria or poses a human health threat. The EU is also reviewing its safety, but only in relation to antibiotic resistance.

Science

Influence of a five-day vegetarian diet on urinary levels of antibiotic and phthalate metabolytes: Korean researchers studying test subjects with at a buddhist diet at a temple retreat have found evidence that a change in dietary behaviour can reduce exposure to a number of environmental chemicals.

Association Between Serum Perfluoroctanoic Acid (PFOA) and Thyroid Disease: Epidemiological study finding an association between non-stick chemicals and thyroid disease.

Neurobehavioral Deficits and Increased Blood Pressure in School-Age Children Prenatally Exposed to Pesticides: A new study reports that prenatal – but not current – pesticide exposure affects children’s neurodevelopment and blood pressure at ages 6 to 8.

Polyethylene Terephthalate May Yield Endocrine Disruptors: Study looking at why PET bottles seem to be a source of exposure to endocrine disruptors finds surprisingly high – and unpredictable – levels phthalates and antimony in liquids stored in the bottles.

Prenatal Phthalate Exposure Is Associated with Altered Childhood Behavior: Study finding “increased loge concentrations of low-molecular-weight (LMW) phthalate metabolites were associated with poorer scores on the Aggression, Conduct Problems, Attention Problems, and Depression, and Externalizing Problems and Behavioral Symptom Index composite scales.”

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