Quantification and Visualization of Fungal Degradation of Polyurethane Foam in Homes

Abstract

People spend 90% of their time in the indoor environment including homes. Homes contain many exposures that can cause harm to human health, and one harmful exposure potentially comes from the degradation of polyurethanes. This deterioration of the polymer causes the release of a carcinogenic compound called 2,4-diaminotoluene (2,4-DAT). Polyurethane foam is a common household material and is used to make many items such as mattresses, couches, insulation, and carpet backing. It is uncertain if growth of fungi on this foam can cause biodegradation to occur, which could potentially result in the release of 2,4-DAT. The goal of this study is to better understand under what conditions one common fungal species, Aureobasidium pullulans, degrades polyurethane foam. We tested the effects of nutrient availability, foam age, and relative humidity levels on the ability of Aureobasidium pullulans to degrade polyurethane foam. The effects of nutrient availability on fungal degradation were evaluated by incubating polyurethane foam with different agars and comparing weight loss of foam samples as a result. The effects of foam age were tested by obtaining 2 foam types; one new and one already used in a home and incubating them to compare weight loss as a result. The effects of relative humidity (RH) on fungal degradation of foam were evaluated by incubating foam at varying equilibrium relative humidity (ERH) levels and performing quantitative polymerase chain reaction (qPCR) to quantify fungal growth. Polyurethane foam incubated with Aureobasidium pullulans was observed under a scanning electron microscope (SEM) in order to visually observe the growth of fungi on polyurethane foam. The ideal conditions for fungal degradation were foam type 1 with an additional carbon source and high RH level. The peak weight loss of foam from fungal degradation was found to be 56% and fungal growth was highest at 100% ERH. Spore chains and fruiting bodies were observed via microscopy wrapped around the foam after incubation indicating Aureobasidium pullulans can grow and reproduce on polyurethane foam given appropriate conditions. This information can be used in the future to prevent fungal degradation of polyurethane foam and potentially decrease carcinogen exposure.