Browsing by Author "Karr, Catherine J."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Heavy metals and neurodevelopment of children in low and middle-income countries: A systematic review
    (PLOS, 2022-03-31) Heng, Yi Yan; Asad, Iqra; Coleman, Bailey; Menard, Laura; Benki-Nugent, Sarah; Were, Faridah Hussein; Karr, Catherine J.; McHenry, Megan S.; Pediatrics, School of Medicine
    Background: The presence of harmful environmental exposures, which disproportionately affects low-and-middle income countries (LMICs), contributes to >25% of deaths and diseases worldwide and detrimentally affects child neurodevelopment. Few resources succinctly summarize the existing literature on this topic. Our objective is to systematically review and characterize the evidence regarding the relationship between heavy metals and neurodevelopment of children in LMICs. Methods: We conducted a medical librarian-curated search on multiple online databases to identify articles that included individuals <18 years living in a LMIC, quantitatively measured exposure to a heavy metal (either prenatal or postnatal), and used a standardized measurement of neurodevelopment (i.e. cognitive, language, motor, and behavior). Reviews, editorials, or case studies were excluded. Results were analyzed qualitatively, and quality was assessed. Results: Of the 18,043 screened articles, 298 full-text articles were reviewed, and 100 articles met inclusion criteria. The included studies represented data from 19 LMICs, only one of which was classified as a low-income country. Ninety-four percent of postnatal lead and all postnatal manganese studies showed a negative association with metal exposure and neurodevelopment, which were the strongest relationships among the metals studied. Postnatal exposure of mercury was associated with poor neurodevelopment in only half of studies. Limited data on postnatal arsenic and cadmium suggests an association with worse neurodevelopment. Findings were mixed for prenatal arsenic and lead, although some evidence supports that the neurotoxicity of lead was amplified in the presence of manganese. Conclusions and potential impact: We found that lead and manganese appear to consistently have a detrimental effect on the neurodevelopment of children, and more evidence is needed for mercury, arsenic, and cadmium. Better characterization of these effects can motivate and inform prioritization of much needed international policies and programs to reduce heavy metal exposures for young children within LMICs.
  • Thumbnail Image
    Item
    Pesticides and neurodevelopment of children in low and middle-income countries: A systematic review
    (Public Library of Science, 2025-06-11) Coleman, Bailey; Asad, Iqra; Heng, Yi Yan; Menard, Laura; Hussein Were, Faridah; Thomas, Melissa R.; Karr, Catherine J.; McHenry, Megan S.; Pediatrics, School of Medicine
    Background: Pesticides are increasingly common in low- and middle-income countries (LMICs), where weaker regulations and multiple risk factors for poor neurodevelopment exist. Due to biological and behavioral factors, children are vulnerable to chronic pesticide exposure at a time when brain development is critical. The objective of this study is to systematically review studies assessing pesticides use with child neurodevelopment in LMICs. Methods: Using terms developed by a medical librarian, a search was performed in June 2023 across online databases, including OVID MEDLINE and EMBASE. For inclusion, studies required a measurement of pesticide exposure and neurodevelopmental outcomes using a standardized tool and study participants ≤18 years within an LMIC, as determined by World Bank criteria. Descriptive analyses were performed using extracted data, including published outcomes of significance. Results were assessed for internal validity and reported by the method of exposure measurement (biomarkers or questionnaires/region of residence). Results: A total of 31 studies spanning 11 LMICs met the inclusion criteria. An adverse association was found between pesticide exposure and at least one domain of neurodevelopment in 23 studies, including 12 studies with child-level measurements, 10 studies with maternal measurements in pregnancy, and one questionnaire-based study. Exposure to organochlorines, carbamates, chlorpyrifos, and fungicides were consistently associated with worse outcomes for neurodevelopment, specifically executive functioning, cognition, motor development, and behavior. Few studies found adverse associations with urine/serum organophosphate levels. Due to the heterogeneity of existing data, we were unable to quantify the relationship between pesticide exposure and neurodevelopment. Conclusions: While studies suggest that some domains of neurodevelopment may be negatively associated with pesticide exposure, extrapolation is limited due to the challenges in measuring pesticide exposure within these contexts and differing study designs. Several research gaps must be addressed to develop policy and regulations that protect children from potential neurodevelopmental deficits associated with pesticide exposure.