Contribution of Dicofol to the Current DDT Pollution in China

TLDR

High DDT concentrations and a high o,p′‑DDT/p,p′‑DDT ratio in air over Taihu Lake, together with the potential conversion of p,p′‑Cl‑DDT to p,p′‑DDE, suggest that dicofol use north of the lake may be the main source of these DDTs and complicate residue‑time assessments. The study aimed to test this hypothesis by analyzing 2003 dicofol samples for DDT impurities and highlighted the need for further research on p,p′‑Cl‑DDT in the environment. The authors collected 2003 dicofol samples to quantify DDT impurities and, using production and distribution data, estimated 8,770 t of DDTs entered the environment from dicofol use between 1988 and 2002. The o,p′‑DDT/p,p′‑DDT ratio in dicofol samples was 7.0, matching lake air values, and the samples contained 114, 69, 44, and 17 g kg⁻¹ of o,p′‑DDT, p,p′‑Cl‑DDT, o,p′‑DDE, and p,p′‑DDT, indicating that dicofol‑derived DDT pollution—characterized by high ratios—is likely significant in southern and eastern China.

Abstract

High DDT concentrations and o,p‘-DDT/p,p‘-DDT ratios observed in the air over Taihu Lake, a lake near Shanghai, China, led us to suggest that current use of dicofol in the area north of the lake was the main source of the measured DDTs. To examine this hypothesis, samples of commercially available formulated dicofol in China were collected in 2003 to measure the impurities of DDT related compounds (DDTs). The o,p‘-DDT/p,p‘-DDT ratio in the samples was 7.0, close to the observed value in the air over Taihu Lake. Average contents of o,p‘-DDT, p,p‘-Cl-DDT, o,p‘-DDE, and p,p‘-DDT in the samples were 114, 69, 44, and 17 g per kg dicofol, respectively. On the basis of a production and distribution survey, total input of DDTs to the environment from the dicofol use in China was estimated to be 8770 t between 1988 and 2002. “Dicofol type DDT pollution”, defined as DDT pollution caused by dicofol use and characterized with high o,p‘-DDT/p,p‘-DDT ratio, might be serious in China, especially in southern and eastern China. The conversion of p,p‘-Cl-DDT to p,p‘-DDE can lead to high p,p‘-DDE/p,p‘-DDT ratio and could mislead the evaluation of p,p‘-DDT resident time in the environment. Therefore, more studies on p,p‘-Cl-DDT in the environment are needed.