We often think of pollution as an outdoor problem. But many office workers are constantly breathing a complex soup of invisible airborne substances including ozone, carbon dioxide, particulate matter and volatile organic compounds (VOCs). The latter are gases that can be released from moulds, building materials, human metabolismand personal care products such as lotions, deodorants, hair spray and cosmetics. Some VOCs have been linked to health effects including fatigue, difficulty concentrating, eye, nose and throat irritation, and even cancer. Whether exposure to these substances in offices poses a significant risk to human health remains an open question, however. Benjamin Franklin suspected the unhealthy effects of indoor air back in 1785. I am persuaded that no common Air from without, is so unwholesome as the Air within a close Room, that has been often breathd and not changed, he wrote in a letter to Dutch physician Jan Ingenhousz. Over the years scientists have tried to back up his claim, and recent research provides some support for it. In one of the largest studies of its kind, researchers at Purdue University have now used a sophisticated system of sensors to measure the complex dynamics of VOCs in an office environment. The findings, presented in October at the American Association for Aerosol Research Conference in Portland, Oregon, cannot prove that any one indoor air component causes health problemsbut they could be used to design better-ventilated offices and advance research on the issue. The study took place at Purdues Living Labs, a simulated open office equipped with thousands of sensors as well as an instrument called The Nose, a highly sensitive mass spectrometer that can sniff out VOCs, ozone, carbon dioxide and aerosols. Researchers used temperature sensors embedded in office chairs to track the occupancy of 20 graduate students who spent their days working there. Brandon Boor, an assistant professor of Civil Engineering at Purdue, and his team found that humans were the dominant source of VOCs in the model offices air. Nearly 2,000 such compounds can come from simply being alive: exhaled breath, sweat, saliva and the like. Concentrations of human-derived VOCs varied throughout the day in the experiment, but usually peaked in mid-afternoon when occupancy was highest. VOC concentrations also depended on factors such as whether the office had recently been cleaned, whether someone had just applied a personal care product, and how well the ventilation system was working. Ozone gas from the outside airwhich came in through the ventilation systemwas highly reactive with indoor surfaces such as walls and furniture, and with VOCs left behind by occupants. The researchers found that the gas reacted with human skin oil to create new VOCs. It also reacted with chemicals called monoterpenes from a freshly peeled mandarin orange to form new, nanometre-sized ultrafine particles. (Monoterpenes can also come from manufactured sources such as scented personal care products and cleaning fluids.) The investigators further found that VOCs from personal care products peaked in the morning, when freshly deodorized graduate students arrived. A chemical called D5found in thousands of such productswas detected at levels comparable to or greater than those of isoprene, one of the major VOCs in exhaled human breath, and was relatively high in the staff hangout area. The team also detected related compounds called D4 and D6, but these were found at much lower levels than D5. Our preliminary results suggest that similar amounts of isoprene and D5 can be released into the office air, Boor says. The emissions of D5 are likely dependent on the amount and type of personal care products the occupants are wearing. He notes that results from his study apply only to this model office. His team is working on emission factors that may allow them to generalise their results to other settings. Office workers may not have a lot of control over how much carbon dioxide their co-workers exhale, how much skin oil they produce, or even whether they decide to peel an orange. But they do have some control over their own use of personal care products, says Carrie Redlich, a pulmonologist and director of the Occupational and Environmental Medicine Program at Yale School of Medicine. If someone is symptomaticmaybe they have a headache or their asthma is acting up in an environment where people are wearing a lot of perfumed products, the question is: Do we really need [these products]? she asks. Ive seen enough patients who are very symptomatic in response to those [substances]. In some jobs, people may not be able to get up and walk away from whats triggering their symptoms, and it may really impact their ability to keep that job.
Researching the Chemical Risks
Some research suggests that compounds such as D4, D5 and D6which are derived from silicone and called cyclic volatile methyl siloxanes (cVMSs)could pose a risk to human health, although the vast majority of studies have been done on animals and are far from definitive. D4, D5 and D6 are all found in personal care products, and D5 is most abundant. Animal studies have linked D4 to impaired fertility, and both D4 and D5 to uterine cancer. But the animals were subjected to very high doses of the chemicals, for long durations and in highly unusual settings, according to Charles McKay, the former president of the American College of Medical Toxicology and current associate medical director of the Connecticut Poison Control Centre at the University of Connecticut Health Centre. Those experimental conditions often have very little to do with human exposure to much, much lower doses, McKay says. Studies did show uterine cancer issues in one animal model at very high doses, but Im not sure that has any bearing on the human setting. (McKay has been retained previously by law firms representing pharmaceutical and medical device companies or their opponents, but with the exception of one case involving a car wax product, these cases were not related to cVMS compounds.) Most of the animal studies have been sponsored by the silicone industry, and those that showed a connection with uterine cancer were done in rats. Industry representatives have argued the hormonal mechanism that may contribute to uterine cancer after exposure to D4 and D5 is different in rats than in humans, so studies of the former may not be relevant to the latter. Critics point out the industry ties and the dearth of independent studies. As a common pattern, if facts of concern are found, the industry launches a firework of publications that try to downplay such results and to argue that the results of rat studies are not relevant to humans for various reasons, usually published as half a dozen sponsored papers in special [perhaps paid] issues of journals that at least have a reputation of being close to industry, says Christoph Rücker, a chemist at Leuphana University Lüneburg in Germany, and co-author of a review study about siloxanes. The European Union recently decided to regulate these compounds. Citing environmental risks, the EUs REACH program has listed D4, D5 and D6 as substances of very high concern, and labelled them as PBT (persistent, bioaccumulative and toxic) and vPvB (very persistent, very bioaccumulative). Starting after January 31, 2020, the EU will limit D4 and D5 concentrations to 0.1 percent in wash-off products such as shower gels, shaving foams and shampoos. The EU has also proposed restricting D4, D5 and D6 in all consumer and professional products, such as dry-cleaning fluid. The silicone industry has sued the European Court of Justice over these actions. Linda Loretz, chief toxicologist for the Personal Care Products Council (a national trade association) and Karluss Thomas, senior director of the Silicones, Environmental, Health, and Safety Centre (a subgroup of the American Chemistry Council that represents 90 percent of silicone chemical manufacturers in North America) point out the large body of research reviewed by regulatory bodies in a number of countries including the U.S. Environmental Protection Agency. Loretz and Thomas say D4 and D5 do not pose risks to human health, although some of the research is inconclusive. Studying cVMSs and human health is complex and controversial, according to Rücker. Few studies have been conducted in humans, and not much research has been conducted in the past 10 years. There are only [a handful] of experts on toxicity of siloxanes, and these are employees of the silicone industry, Rücker says. The industry is free to publish or not to publish the results of their studies. These compounds have been used in consumer products for almost 80 years. Children may have higher exposures than adults, with relatively high concentrations in baby products. Siloxanes are clearly one of the major contaminants in indoor air and dust, [which] form an important pathway of human exposure, says Kurunthachalam Kannan, deputy director of the Division of Environmental Health Sciences at New York State Department of Healths Wadsworth Centre. But assessing risk to humans for these compounds is sometimes politically sensitive, he says. Whether or not these specific chemicals prove to be a risk, office workers could benefit from a little fresh air. Benjamin Franklin would throw open the windows, throw off his clothes and take so-called air baths. But if office heating, ventilation and air conditioning systems are functioning adequately, people may not need to strip down. Their co-workers may thank them for it.
Scientific American, 21 November 2019