No federal safe mold spore count exists, so tenants, buyers, and courts have no objective threshold to prove a home is unsafe

The EPA, OSHA, NIOSH, and CDC have all declined to set a threshold limit value (TLV) for indoor mold spore concentrations. The EPA explicitly states it does not recommend mold testing standards for consumer use. This means there is no legally defensible number — no 'safe level' of mold spores per cubic meter — that a tenant can point to when demanding remediation, that a buyer can cite when backing out of a purchase, or that a court can use to determine liability. This matters because without a threshold, every mold dispute devolves into a battle of expert witnesses. A tenant's industrial hygienist says 2,000 spores/m3 of Aspergillus is dangerous; the landlord's expert says it is within normal range. Neither is wrong, because there is no standard. Judges and juries have no framework to evaluate these claims. The result is that tenants with legitimate mold exposure spend $5,000-$15,000 on legal and testing fees just to reach a settlement, while landlords with no actual mold problem face nuisance suits they cannot cheaply disprove. The absence of a standard hurts both sides. This vacuum persists because mold's health effects are highly individual — a spore count that triggers asthma in one person may be harmless to another. The EPA has stated that establishing a numerical standard would create a false sense of precision. But the practical consequence is that the entire mold dispute ecosystem — insurance claims, tenant complaints, real estate transactions, and litigation — operates without any objective measuring stick, forcing every case into expensive, subjective expert testimony.