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The Microbial Degradation of DDT and Potential Remediation Strategies
Published in M.H. Fulekar, Bhawana Pathak, Bioremediation Technology, 2020
The initial attack on DDT is on the trichloroalkyl backbone, after which the molecule is typically converted to DDD under anaerobic, and DDE under aerobic, conditions. Although DDT degradation has occurred at sites contaminated with DDT, the subsequent metabolites (DDD and DDE) accumulate and are limited to further degradation (Aislabie, 1997). Degradation rates and concentrations of transformation products depend on the soil conditions, water content, and the microbes present in the soil (Aislabie, 1997). Under anaerobic conditions, DDD is produced from DDT by reductive dechlorination. This process may proceed by either chemical or biological reduction (Zoro et al., 1974; Baxter, 1990). Under aerobic conditions, DDE is formed from DDT via dehydrodechlorination (Pfaender and Alexander, 1972). It should be noted that it is difficult to account for all DDT metabolites in complex environmental systems (Guenzi and Beard, 1967; Burge, 1971; Jensen et al., 1972). The major microbial biotransformation products of DDT are presented in Table 1.1.
Toxicity of Pesticides
Published in Lorris G. Cockerham, Barbara S. Shane, Basic Environmental Toxicology, 2019
Some organochlorine insecticides such as the o, p′-isomer of DDT, methoxychlor, and chlordecone have been shown to cause estrogenic effects by binding to estrogen receptors following chronic exposure. Reproductive toxicity has also been reported in birds, rodents, and possibly humans. Carcinogenicity data has also been generated for some of the organochlorine insecticides, but much of the data is unconvincing. If any of these compounds are truly carcinogenic, they are weakly so and act by epigenetic and not genotoxic mechanisms. None of these chronic effects have been well studied in environmentally relevant species. However, these specific chronic effects are of concern in environmental toxicology because of the potential for bioaccumulation and environmental persistence of these chlorinated insecticides. The half-life of DDT in the environment is at least 10 years and one of its metabolites, DDE, persists for decades, as do lindane and heptachlor (Duffus, 1980). At least 2.5 years are required for aldrin and dieldrin to degrade to 95% of their original concentration. Even though DDT was banned in 1972 and virtually all uses of the other organochlorine insecticides have been halted in the U.S., other countries still permit their use, so they continue to accumulate within the environment. However, even within the U.S., hot spots of organochlorine residues exist, either as the result of historical heavy usage in the area or from the use of illegally imported organochlorine insecticides (Hall, 1987). The environmental burden of DDT has been estimated at 1 × 109 lb (Kohn, 1987).
Rainwater Harvesting under a Warming Climate and Effects of Algae on Changes to Water Storage Levels
Published in Mark Anglin Harris, Confronting Global Climate Change, 2019
Studies in animals given DDT with food have shown that DDT can cause liver cancer (WSDH 2018). Studies in DDT-exposed workers did not show increases in cancer. However, it has been determined to be a probable human carcinogen by the Department of Health and Human Services, the International Agency for Research on Cancer, and the Environmental Protection Agency (EPA) (WSDH 2018). The EPA has determined that DDE and DDD (an environmental metabolite of DDT) are also probable human carcinogens (WSDH 2018).
Aerobic Biodegradation of DDT by Advenella Kashmirensis and Its Potential Use in Soil Bioremediation
Published in Soil and Sediment Contamination: An International Journal, 2018
Chiraz Abbes, Ahlem Mansouri, Naima Werfelli, Ahmed Landoulsi
At the beginning of the experiment, we detected the presence of DDD and DDE. Several studies have shown that both products are highly toxic (ATSDR 2002). The Department of Health and Human Services (DHHS) has determined that DDD and DDE may reasonably be anticipated to be human carcinogens (NTP 2002). The International Agency for Research on Cancer (IARC) has determined that DDD and DDE are possibly carcinogenic to humans (IARC 2002). These classifications are based on sufficient evidence of cancer in animals. Other toxic effects have been observed, such as hepatotoxicity and neurotoxicity (ATSDR 2002). DDD and DDE may have endocrine disrupting potential, affecting the reproductive system, although the effects may vary among animal species in correlation with exposure levels (Harada et al.2016). Indeed, p-p'DDE inhibits androgen binding to the androgen receptor (Kelce et al.1995). Recent results suggest that mild and unspecified gastrointestinal symptoms with no clear causes could be related to pp-DDD levels (Kim et al.2017).
Environmental contaminants and preeclampsia: a systematic literature review
Published in Journal of Toxicology and Environmental Health, Part B, 2018
Emma M. Rosen, MG Isabel Muñoz, Thomas McElrath, David E. Cantonwine, Kelly K. Ferguson
In the 1970s, the United States Environmental Protection Agency (US EPA) banned DDT, a powerful insecticide, due to evidence suggesting adverse effects on humans and the environment (Hanssen et al. 2013). However, DDT continues to be used to combat malaria in South America, Africa, and Asia (van den Berg 2009). DDE is a metabolite of DDT that persists and might also exert harmful health effects (van den Berg 2009).