Issue link: https://hi.iaq.net/i/584598
IAQA 18th Annual Meeting & Indoor Environment and Energy Expo (IE3) The views and opinions herein are those of the volunteer authors and may not reflect the views and opinions of IAQA. The information is offered in good faith and believed to be reliable but it is provided without warranty, expressed or implied, as to the merchantability, fitness for a particular purpose or any other matter. early in life may reduce allergic responses later in life. This would support the "hygiene hypothesis", which hypotheses that the lack of early childhood exposure to infectious agents, symbiotic microbes, and parasites increases susceptibility of allergic diseases by suppressing the natural development of the immune system. Study Design Endotoxin and mold samples were collected in residential buildings to investigate whether a relationship exists between the presence of mold/moisture and endotoxin. IAQ investigators collected typical spore trap and surface tape lifts to determine moldiness of the homes. At the same time dust samples were sampled in the homes and submitted to the lab for extraction and testing. The most widely used lab method is the Kinetic Chromogenic LAL Assay that expresses endotoxin results as endotoxin units (EU) per mg of dust. In all, twelve homes were sampled in New Jersey and Pennsylvania. Three endotoxin samples were collected in each dwelling from a variety of locations as determined by the individual investigator. Locations included the floors in the kitchen, living room, bedroom and basement as well as the sofa. Collection was with a 0.45 micro polycarbonate filter in a 37 mm styrene housing that had been sterilized by irradiation and certified as "endotoxin-free". The house dust was sifted through a 350 micro sieve to remove large debris then the fine dust used for endotoxin extraction. The kinetic chromogenic LAL assay for detecting the endotoxin uses blood (amoebocyte) extracts from the horseshoe crab (Limulus). A researcher studying blood in the horseshoe crab found that certain infections (specifically Gram negative bacteria) caused the blood to clot. Their white blood cells could detect the presence of the bacteria by the endotoxin and then would release a clotting agent called coagulogen. This clotting action prevented the spreading of the bacteria through the blood to other parts of the crab. Commercialization of this phenomenon includes, harvesting the crabs, bleeding them, and then returning them to their habitats. The white blood cells are separated from the rest of the blood then lysed to release the clotting agent. This was accepted by the FDA in the 70's for pharmaceutical industry use and is much faster (45 mins) versus the old way of injecting rabbits then waiting 48 hrsto see if they developed a fever. Study Results Nine of the twelve homes studied had visible mold growth. Sampling those surfaces showed Aspergillus, Chaetomium, Penicillium, and Stachybotrysas the predominant fungi. Spore trap samples indicated that eight of the twelve homes had elevated indoor spore counts compared to outdoor baseline samples. When comparing these homes we considered the nine homes with visible mold to be "moldy" and the 3 with no visible mold to be "non-moldy". The endotoxin levels in the dust from moldy homes ranged from 0.1-263.6 EU/mg and in the non-moldy homes from 0.5-38.5 EU/mg. Although the mean appears higher it was not significantly higher in moldy versus the non-moldy homes (Figure below). Published ranges from other researchers found between 11- 100 EU/mg of dust. 0 2 4 6 8 10 12 Mouldy Non-mouldy Endotoxin Values (EU per mg dust) Type of Home Comparison of Endotoxin Levels in Dust in Mouldy and Non- mouldy Homes Geo Mean