Estimating Exposure to DDTs and Potential Carcinogenic and Non-carcinogenic Risks among Breast-fed Infants

摘要

Background: Breast milk consumption is the primary route of infant exposure to certain lipophilic toxicants such as organochlorine pesticides (OCPs). Dichlodiphenyl-trichloroethane (DDT) as the main type of OCPs has been associated with endocrine disruption and several cancers in many experimental and epidemiological studies. Objectives: Because of the potentially serious health risk posed to newborn infants by the exposure to DDTs through breast milk feeding at a time of rapid development and growth, the present study has attempted to estimate the extent of carcinogenic and non-carcinogenic risk. Methods: In the present study, breast milk samples were collected from 50 lactating mothers in the first week of post-partum from Tehran on May, 2015 and evaluated for DDT metabolites including p,p'-DDT, p,p'-DDD, p,p'-DDE, o, p'-DDE using GC-MS method. Subjects' mean age was 29+6 years, ranging from 18 to 42 years. All infants were exclusively breast-fed. For exposure assessment, daily intake was estimated based on the concentration of analytes and the assumption of a daily breast milk consumption rate of 700 g/day for a neonate weighing 5 kg. For the non-carcinogenic risk assessment purposes, hazard quotients were calculated. For carcinogenic risk assessment estimation, the cancer benchmark concentrations (CBC) were derived using oral slope factors and their hazard ratios (HR). Results: p,p'-DDT, p,p'-DDD, p,p'-DDE, o, p'-DDE were detected in all breast milk samples, with a IDDTs mean concentration of 0.026±0.004 ug/g lipid wt, and ranged between 0.004-0.03 ug/g lipid wt, suggesting past usage and long-term accumulation of DDTs in humans. In addition, the DDT/DDE ratio was lower than one (mean: 0.021), which also indicates a historical exposure to this pollutant. A daily intake estimate of IDDTs, through breast milk consumption was 0.032 ug/kg per day. The highest intakes were recorded for p,p'-DDE ( 0.02 ug/kg-day) whilst the lowest was for p,p'-DDD, (0.003 ug/kg-day). The HQ for average DDTs concentrations was found to be low (0.002). HQ lower than 1 was noted for IDDTs, indicating these compounds were not a threat to the health of any breast-fed infant. Also, hazard ratio obtained for p,p'-DDE, p,p'-DDT, p,p'-DDD in breast milk could not pose potential carcinogenic risk to breast-fed infants since all HRs were lower than 1. Our study results reveal infants' exposure to low levels of DDTs through breast milk consumption. However, infants as the vulnerable group might be subject to the potential additive and/or synergistic health effects from the other xenobiotic chemicals present in breast milk.