tetrachloroanisole, more properly 2,3,4,6-tetrachloroanisole, or TeCA, is a musty- or dusty-smelling compound that can taint wine if the concentration is above the perception threshold of around 20 ng/l in red or white wine and 4 ng/l in water. It is caused by the microbial degradation by fungi in the winery of pentachlorophenol (PCP) used in wood-treatment products. PCA or 2,3,4,5,6-pentachloroanisole has a much higher perception threshold, at around 5000 ng/l, but is nearly always present with TeCA.
