Accidental release of 2,3,7,8-tetrachlorodibenzo- p-dioxin (TCDD) at Sèveso, Italy : V. Environmental persistence of TCDD in soil

TCDD levels were determined at 44 soil sites in Zone A during three surveys carried out at different times (1, 5, and 17 months) after the ICMESA accident. The data obtained provide statistically significant ( P < 0.01) evidence that the geometric mean of TCDD levels dropped to about one-half in the unworked soil of Zone A in the first 5 months after the accident. Following this period, no further decreases in TCDD levels were detected. One month after the accident, TCDD half-life 1 was about 1 year, whereas 17 months after the accident, it was estimated to be > 10 years.