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Environmental Chemistry
Published in Benjamin Alter, Environmental Consulting Fundamentals, 2019
Among the chemicals with primary drinking water standards is one of special note—2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Although 2,3,7,8-TCDD is commonly referred to as dioxin, dioxin actually refers to a family of chemical compounds that are generally considered to be among the most hazardous to human health and the environment. Dioxins are unwanted byproducts in the manufacture of organic pesticides or incomplete combustion. They became infamous in United States and across the world as a contaminant in Agent Orange, a defoliant used in the Vietnam War. Generally comprised of two benzene rings connected by oxygen “bridges,” with two chlorine atoms at each end of its atomic structure. The chlorine atoms contribute greatly to the toxicity of the molecule. Figure 4.17 shows the molecular structure of a dioxin molecule.
Risk Characterization
Published in Ted W. Simon, Environmental Risk Assessment, 2019
The herbicide Agent Orange was used extensively in Vietnam as a defoliant. Agent Orange contained 2,4,5-trichlorophenoxyacetic acid and a contaminant generated during manufacture, 2,3,7,8-tetrachlorodibenzo-p-dioxin, or TCDD. TCDD is highly persistent in the environment, and many parts of Vietnam remain contaminated.113 Da Nang is the largest city in central Vietnam, and was the location of a US airbase during the Vietnam conflict in the 1970s. The chair of the People’s Committee of Da Nang City was made aware of EPA’s current toxicity criterion for TCDD based on the possibility of congenital hypothyroidism in infants due to reduced maternal thyroid-stimulating hormone (TSH).
The influence of row unit settings and ground speed of modern spindle-type harvesters on cotton fibre and seed quality
Published in The Journal of The Textile Institute, 2021
The cotton variety was Sicot 74 BRF (Stiller, 2010), which was the most popular Upland variety grown in Australia during that time. The field was subjected to standard management practices for irrigated Upland cotton in Australia. The field was first subjected to harvest aids by air, with a mixture of leaf defoliant (0.20 L ha−1 Dropp® liquid from Bayer Crop Science), boll opener (2.0 L ha−1 Prep™ from Bayer Crop Science), and defoliant aid spray (0.5 L ha−1 of Hasten TM from Victorian Chemical Company). It was sprayed by air for a second time with the same mixture of leaf defoliant (0.20 L ha−1 Dropp® liquid from Bayer Crop Science), boll opener (2.0 L ha−1 Prep™ from Bayer Crop Science), and defoliant aid spray (0.5 L ha−1 of Hasten TM from Victorian Chemical Company).
Agromyces and Arthrobacter isolates from surficial sediments of the Passaic River degrade dibenzofuran, dibenzo-p-dioxin and 2-monochlorodibenzo-p-dioxin
Published in Bioremediation Journal, 2021
Haider S. Almnehlawi, Rachel K. Dean, Staci L. Capozzi, Lisa A. Rodenburg, Gerben J. Zylstra, Donna E. Fennell
The highly urbanized Lower Passaic River has been polluted by industrial contaminants including heavy metals, polychlorinated biphenyls (PCBs), and the CDD/Fs, over many decades (Bopp et al. 1991; Iannuzzi 2002). The lower 8.3 miles of the river is characterized by high levels of 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD), one of the most toxic CDD congeners (van den Berg et al. 2013). TCDD was historically formed as a side product during production of 2,4,5-trichlorophenol (2,4,5-TCP) which was a precursor to produce 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) (Langer, Brady, and Briggs 1973; Parette, Velinsky, and Pearson 2018), a component of the defoliant Agent Orange, a herbicide mixture containing 2,4,5-T. Historic discharges of chemical sludges to the river are the primary sources of TCDD, along with stormwater runoff (Bopp et al. 1991; Bopp et al. 1998; Israelsson, Quadrini, and Connolly 2014). Other sources of CDD/Fs to the river include atmospheric deposition from incineration and combustion processes and combined sewer overflows (Ehrlich et al. 1994; Iannuzzi et al. 1997; Tu et al. 2011; Parette, Velinsky, and Pearson 2018; Khairy, Barrett, and Lohmann 2016). Despite cessation of industrial production that discharged TCDD in the 1970s, high concentrations of this and other CDD/Fs are still present (Bopp et al. 1991; Fiedler 2007; Parette, Velinsky, and Pearson 2018) and the chemical signature is detected in the surrounding tidal area, depending on the distance from the original source.
Progresses and emerging trends of arsenic research in the past 120 years
Published in Critical Reviews in Environmental Science and Technology, 2021
Chengjun Li, Jiahui Wang, Bing Yan, Ai-Jun Miao, Huan Zhong, Wei Zhang, Lena Qiying Ma
Although arsenic-induced health problems were reported for a long time, they failed to attract much attention until the 1960s when relevant studies about arsenic exploded. Arsenical products had a wide range of applications in the early 20th century, and the categories of arsenical products, such as arsenical pesticide, herbicide and defoliant sprays (Bishop & Chisholm, 1962) and even feed additives (Morrison, 1969) continued to increase. Such extensive use led to the build-up of arsenic in the environment, e.g., contaminated soil (Hiltbold et al., 1974) and water (Angino et al., 1970), with arsenic eventually accumulating in animals and humans (Schroeder & Balassa, 1966) via trophic transfer (Morrison, 1969).