Tracking this here: https://github.com/publiclab/wherewebreathe/issues/123

Formaldehyde Exposure

Formaldehyde is a colorless, flammable gas with a distinct odor. Current common sources of formaldehyde in the home include wood floor finishes, pressed-wood products, wallpaper and paints, and the combustion and oxidation of other hydrocarbons (including cigarettes, oil, natural gas, and emissions from laser printers and photocopiers). The formaldehyde in these products can off-gas into the surrounding environment and be inhaled.

The US Agency for Toxic Substances and Disease Registry (ATSDR) maintains toxicological profiles for a number of substances, including formaldehyde. The following chart (Figure 1) summarizes the scientific evidence on the health effects of varying concentrations of formaldehyde exposure as most recently updated by ATSDR in 2010. In their home environments, participants in the WWB study are most likely to be exposed at lower levels described in this chart (up to 0.6 ppm, or 600 ppb). This summary suggests that there is strong scientific evidence for formaldehyde having a range of human health effects at these lower levels of exposure: nasal and eye irritation, impaired short-term memory, change in pulmonary function, and exacerbation of asthma or allergies.

Figure 1. Existing evidence, health effects of breathing formaldehyde in humans and in animals. Reproduced from Addendum to the Toxicological Profile for Formaldehyde by the Agency for Toxic Substances and Disease Registry, 2010, p. 2.

To these symptoms on which scientific consensus already exists, we add a number of candidate symptoms observed at higher levels of formaldehyde exposure (nausea, headaches, throat and skin irritation, cough, respiratory discomfort) and also those symptoms reported to WWB investigator Nick Shapiro during his fieldwork with individuals living in FEMA-distributed trailers after Hurricane Katrina (insomnia, nightmares, digestive trouble, and changes in sense of smell or taste).

Bibliography:

1.Agency for Toxic Substances and Disease Registry (ATSDR). 1999. Toxicological Profile for Formaldehyde. Addendum to the Profile for Formaldehyde. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service. (2010). 2.Dales, R. E., Schweitzer, I., Bartlett, S., Raizenne, M. & Burnett, R. Indoor Air Quality and Health: Reproducibility of Respiratory Symptoms and Reported Home Dampness and Molds using a Self-Administered Questionnaire. Indoor Air 4, 2–7 (1994). 3.Hanrahan, L. P., Dally, K. A., Anderson, H. A., Kanarek, M. S. & Rankin, J. Formaldehyde vapor in mobile homes: a cross sectional survey of concentrations and irritant effects. American journal of public health 74, 1026–7 (1984). 4.Kanazawa, A. et al. Association between indoor exposure to semi-volatile organic compounds and building-related symptoms among the occupants of residential dwellings. Indoor Air 20, 72–84 (2010). 5.Liu, K. S., Huang, F. Y., Hayward, S. B., Wesolowski, J. & Sexton, K. Irritant effects of formaldehyde exposure in mobile homes. Environmental health perspectives 94, 91–4 (1991). 6.Mori, M. et al. Changes in subjective symptoms and allergy state among medical students exposed to low-level formaldehyde 6 months after completion of a gross anatomy dissection course. Environ Health Prev Med 18, 386–393 (2013). 7.Ritchie, I. M. & Lehnen, R. G. Formaldehyde-related health complaints of residents living in mobile and conventional homes. American journal of public health 77, 323–8 (1987). 8.Sahlberg, B., Norbäck, D., Wieslander, G., Gislason, T. & Janson, C. Onset of mucosal, dermal, and general symptoms in relation to biomarkers and exposures in the dwelling: a cohort study from 1992 to 2002. Indoor Air 22, 331–338 (2012). 9.Saijo, Y. et al. Symptoms in relation to chemicals and dampness in newly built dwellings. International archives of occupational and environmental health 77, 461–70 (2004). 10.Takigawa, T. et al. Relationship between indoor chemical concentrations and subjective symptoms associated with sick building syndrome in newly built houses in Japan. Int Arch Occup Environ Health 83, 225–235 (2010). 11.Thun, M. J., Lakat, M. F. & Altman, R. Symptom survey of residents of homes insulated with urea--formaldehyde foam. Environmental research 29, 320–34 (1982). 12.Wargocki, P., Wyon, D. P., Baik, Y. K., Clausen, G. & Fanger, P. O. Perceived air quality, sick building syndrome (SBS) symptoms and productivity in an office with two different pollution loads. Indoor air 9, 165–79 (1999).

Remediation

Domestic chemical ecologies have both many toxicant sources and many toxicant sinks. Formaldehyde slowly and silently off gasses from engineered woods, carpets, and permanent press clothing. Some of these silent emissions waft out open windows. Others are absorbed by human bodies or the bodies of companion species. Others still are metabolized by decorative indoor plants and the microbes that inhabit their roots.

Since the 1990s we have been hearing promises of plant-based air filters. See, for example, this patent filed in 1993. Some critics (see this this 2009 critical review) find fault in the claim that plants-on-their-own can clean indoor air and state that the average home would need 680 plants to adequately scrub the air of toxicants.

Increasing the Airflow

Research indicates that it is not so much that different plants remediate the air differently, but that different plants cultivate different rhizospheric conditions by their root exudates and root autolysis. Plants with quantitatively more bacteria dwelling in their rhizosphere won’t remediate as much atmospheric formaldehyde as plants with fewer overall microorganisms amongst their roots but more gram-negative rods. The formaldehyde removal capacity of plants and their bacterial companion species increases as exposures increase, and over time the bacteria appear to “acquire an increased taste” for exposed toxicants and up-regulate their metabolism. Phyto-bio remediation does not appear to be reaction-limited but diffusion-limited. The amount of air breezing through the roots and across the leaves of indoor plants is minimal. The Public Lab DIY Indoor Air Remediation Kit builds upon these observations that, at least in theory, increasing the airflow through the root system could increase the remediation capacity of plants by upwards of 200 fold. Plant air scrubbers would not require the intermittent replacement replacement of filters but would become more efficient overtime.

Plants manage decomposition underground by providing sugars to symbiotic and beneficial fungi and bacteria in order to manage root growth and decomposition. Plants spend more energy below ground than above ground, and seasonally grow and kill roots just like leaves. We're piggy backing on this process, using plant-managed colonies of beneficial bacteria to scrub formaldehyde, a naturally occurring product of decomposition.

While there is evidence on both sides to indicate either the efficacy or inefficacy of plants-on-their-own as indoor air filters, there have been no published studies on the efficacy of plant systems with increased airflow, like the prototype offered by Public Lab. A similar $230 system made by a for profit company claims that it can clean a 10'x14' room in an hour. Some interior-landscaping industries suggests that 1 regular plant on its own (which could be 200 times less efficient than the Public Lab prototype) per 100 sq feet. critics say its more like 45 regular plants per 100 feet (surprise! you live in a greenhouse now!) so that would be 680 plants in a 1500 sq foot house. But if our system lives up to the theory you could have just three planters to maintain clean air across your home or one in your bedroom or one in the office. During the development of our remediation tool we found a 40% reduction of formaldehyde in a two bedroom with a single planter.

For our system you will need to add a plant -- we suggest Golden Pathos or Snake Plant (Sansevieria) because of their metabolic efficiency and hardiness. Here are a few other plants that have been show to reduce ambient formaldehyde loads: Dwarf date palm