Academic journal article Environmental Health Perspectives

Aerial Application of Mancozeb and Urinary Ethylene Thiourea (ETU) Concentrations among Pregnant Women in Costa Rica: The Infants' Environmental Health Study (ISA)

Academic journal article Environmental Health Perspectives

Aerial Application of Mancozeb and Urinary Ethylene Thiourea (ETU) Concentrations among Pregnant Women in Costa Rica: The Infants' Environmental Health Study (ISA)

Article excerpt

Introduction

Banana export, primarily to the United States and Europe, is an important economic activity in Costa Rica, constituting 2.2% of the country's gross domestic product and a source of employment for more than 40,000 workers [Corporacion Bananera Nacional (CORBANA) 2012]. To protect banana plants from diseases such as black sigatoka, > 2 million kg of pesticides are applied annually on 40,000 hectares (Bravo et al. 2013; CORBANA 2012). The fungicide mancozeb, a manganese-zinc complex of ethylene-bis-dithiocarbamate (EBDC), comprises about half of the pesticides used and is applied weekly by light aircraft (Figure 1) (Barraza et al. 2011; Bravo et al. 2013). To our knowledge, no other EBDCs are being used on these plantations (Bravo et al. 2013). Mancozeb is a commonly used fungicide throughout the world, registered for use in almost 120 countries (Gullino et al. 2010). In the United States, approximately 3.4 million kg of mancozeb are applied annually in agriculture (National Toxicology Program 2014).

EBDCs are absorbed by skin, mucous membranes, and respiratory and gastrointestinal tracts, and metabolized via hepatic microsomal enzymes to produce ethylene thiourea (ETU) (Houeto et al. 1995). ETU is rapidly absorbed via the gastrointestinal tract, subsequently filtered by kidneys, and excreted in urine (World Health Organization 1988). ETU is also present as a 0.01-4.5% impurity in EBDC formulations (Camoni et al. 1988; Lindh et al. 2008).

Although both mancozeb and ETU possess low acute toxicity [U.S. Environmental Protection Agency (EPA) 2005], neuroblastic necrosis and hydrocephaly have been reported in ETU-exposed rat embryos at doses far lower than those that caused observable toxic signs in the rat dam (Khera 1987). ETU also is a known inhibitor of thyroid peroxidase activity and alterations in thyroid weight, cells, hormones, and iodine uptake, and thyroid tumors have been reported in chronic mancozeb- and ETU-exposed rats, mice, and dogs (Axelstad et al. 2011; Belpoggi et al. 2002; Chhabra et al. 1992; International Agency for Research on Cancer 2001).

Two cross-sectional studies of EBDC-exposed Mexican backpack applicators (n = 49) (Steenland et al. 1997) and Philippine banana plantation workers (n = 57) (Panganiban et al. 2004) have reported higher mean serum thyroid-stimulating hormone (TSH) concentrations compared to nonexposed workers, although the difference was not statistically significant for the Philippine banana workers. In addition, the Mexican sprayers had higher mean sister chromatic exchanges and chromosome translocations than those who were nonexposed (n = 31), suggesting that cytogenic effects may be associated with EBDC exposure (Steenland et al. 1997). Panganiban et al. (2004) reported a positive correlation between ETU concentrations measured in blood and size of solitary thyroid nodules measured with thyroid gland ultrasounds. Possible effects of mancozeb and ETU on thyroid function are of particular concern for fetal brain development, which requires adequate thyroid hormone secretion: Even mild maternal alterations may affect fetal neurological development (Kester et al. 2004; Patel et al. 2011).

Urinary ETU concentrations are considered a well-established biomarker to evaluate mancozeb and ETU exposures from occupation, environment, and diet (Lindh et al. 2008). Median urinary ETU concentrations in EDBC-exposed workers from vineyards, greenhouses, and potato farms ranged from 2 to 45 [micro]g per gram creatinine (g.cr) (Colosio et al. 2002; Fustinoni et al. 2005, 2008; Kurttio and Savolainen 1990; Sottani et al. 2003). Median urinary ETU concentrations in general populations from Italy, the United Kingdom, and the United States are generally below the limit of detection (LOD) (< 0.5 [micro]g/g.cr) (Aprea et al. 1996; Castorina et al. 2010; Colosio et al. 2006; Jones et al. 2010; Saieva et al. 2004). Detectable urinary ETU concentrations in general populations are thought to be attributable to exposure to EBDCs and ETU from consumption of foods with pesticide residues (Aprea et al. …

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