Interdisciplinary teams address world health and toxics reduction issues with mosquito-repellant clothing and safer colorants in furniture and marine buoys
Chemistry, public health and engineering graduate students worked together to produce three reports for clients Patagonia, Steelcase and Mango Materials in our fall, 2016 Greener Solutions course. Led by School of Public Health professor Dr. Meg Schwarzman, executive director Tom McKeag and BCGC SAGE IGERT fellow Akos Kokai, the three teams reviewed green chemistry, toxicology, professional consulting practices, bio-inspired design concepts and alternatives assessment, before diving into their problem-solving collaboration with the clients.
The challenge for the Patagonia team was to develop a non-toxic, environmentally benign method for a fabric, clothing or a clothing treatment to prevent the biting of the wearer by mosquitoes. The baseline condition that the team investigated was the common industry treatment of polyester with permethrin. Permethrin, although ultimately plant-based, is an insecticide used as a repellant and is toxic to insects and aquatic life when released in the environment. It was expected that all innovative solutions to the challenge would be explored, including chemical, mechanical, and biological.
Three types of mosquitoes and four types of diseases were the focus for the challenge; understanding the behavior of the organisms formed part of the problem definition. The Anopheles mosquito carries the Plasmodium protozoan that causes malaria (over 200 million cases worldwide each year; high morbidity and mortality, increasing resistance to artemisinin treatment). Two types of Aedes mosquito, the Asian Tiger (albopictus) and the Egyptian (aegypti) carry the three viruses of Zika, Dengue Fever, and Chikungunya. Different mosquitoes have different patterns; the Asian Tiger, for instance, is known for aggressive daytime feeding.
The female mosquito has an intriguing array of mechanisms to find her target, starting with detection of CO2 plumes from exhalation, and the 340 different chemicals given off by the human body, to a simple optical system, to heat sensors in its antennae that guide it to the warmth of subdermal capillaries of exposed skin. In addition, researchers have found evidence of olfactory sensors in the proboscis array. The Berkeley team studied all of these mechanisms for a judgment about the most effective interventions while collaborating with Claudia Richardson, Materials Innovation Manager at Patagonia.
The Berkeley team determined that CO2 blocking was the most effective strategy, but a key challenge the team faced in examining textile treatments was the contradictory need for a coating that was both volatile and long lasting. Most natural volatile compounds, such as those found in essential oils, are no longer effective after a matter of a few hours. One of the more promising options was to use a permanent cyclodextrin treatment on the garment, and provide a complementary repellent spray, which the customer could use regularly to refresh the garment’s repellency. Other options included a detergent to refresh repellency, and other textile binding options such as nanoemulsion. The team also delved into some additional clothing scale strategies.
Allison Pieja is the co-founder and CTO of Mango Materials of Berkeley, California. Mango makes the biopolymers PHA (Poly-hydroxyalkanoate ) and PHB (poly-hydroxybutryate) from waste methane. The biodegradable polymer is produced naturally by bacteria grown in fermenters under conditions of excess carbon and limited nutrients. At the end of the polymer product’s life, the polymer can be easily degraded anaerobically to produce methane gas. The gas could be used as a feedstock for additional polymer production affording a closed product/waste life cycle.
Dr. Pieja also wanted to investigate colorants because while PHA is biodegradable, many of the substances added to it for application performance are not. Some of the currently used industrial colorants have properties that are cause for concern. Iron oxide red, for example, is persistent in the environment and has shown evidence of carcinogenic effects. She asked the Berkeley team to propose more benign substitutions for current colorants as might be used in marine buoys.
The Mango team researched several areas in order to prescribe their opportunity map for the company: the PHA substrate, marine buoys and their environments, colorants and current manufacturing processes. The marine buoy application challenge had exacting performance requirements: the same colors that had to be bright, highly visible and long-lasting, also had to be biodegradable and benign. They turned to natural dyes and sources of pigments, recommending paprika, curcumin, chlorophyll and calcium carbonate as substitutions for currently used red, yellow, green and white colorants.
The team found that not all substitutions scored high on both technical and environmental performance. For example, curcumin, a plant-based yellow colorant, while non-toxic breaks down quickly in UV light. Combining it with UV stabilizers could improve its performance, but testing this was beyond the scope of the study and this was one of several recommendations for further study.
Steelcase came to Greener Solutions with a very different problem set. Steelcase is a large and well-established company that makes durable goods like furniture, so sustainable design and development leader Jon Smieja took a long view toward sustainability in proffering his group’s challenge. Could we offer insights into how to make the ultimate Swiss Army knife of molecules, a modular approach to the chemical basis of manufacturing in which a small set of basic elements could be manipulated and reconfigured to offer different performance capabilities, like flexibility or UV protection?
Working closely with Dr. Smieja, the team reconciled this visionary and ambitious challenge with the focus necessary for a successful alternatives assessment. They chose the colorants used for the polypropylene Node chair line as the baseline for substitution and as a test for the concept of modularity. These colorants can be hazardous. For example, carbon black, a common colorant, is a well-known occupational hazard and probable carcinogen.
The team was faced with two distinct but entwined parts of the challenge: finding more benign materials, like torrefied walnut shells for black, and better ways to affix the colorants. Rather than following the current methods of introducing separate colorants to a master batching process, however, they were on the hunt for how they could manipulate the polypropylene itself. They proposed grafting polypropylene, and using maleated polypropylene, and polypropylene binding peptides to achieve this. These strategies are a first step toward the concept of modular polymer manufacturing techniques, but understandably would require alterations to the current manufacturing and recycling processes and are therefore longer-term strategies.