INVESTIGATIONS ON THE STATE OF POPs IN GHANA, AND HUMAN BIOMONITORING OF DIOXIN-LIKE POLYCHLORINATED BIPHENYLS (dlPCBs), POLYCHLORINATED, POLYBROMINATED AND MIXED HALOGENATED DIBENZO-p-DIOXINS AND FURANS (PCDD/Fs, PBDD/Fs, and PXDD/Fs) IN VULNERABLE GHANAIAN POPULATIONS.
Bruce-Vanderpuije, Pennante Naa
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The protection of human health and the environment, from persistent organic pollutants (POPs) is the major objective of the Stockholm Convention. However, in developing countries such as Ghana- one of the top pesticide users and highest POP emitters in sub-saharan Africa. Although the focus has primarily been on determination of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in environmental matrices, there is limited information on how POP concentrations have changed, post ratification of the Stockholm Convention. In addition, human exposure data, on dioxins and dioxin-like compounds (DLCs)- one of the toxic classes of POPs in Ghana are limited. The purposes of this research were to:1) Identify considerations for future research prioritization based on knowledge gaps from previously completed studies by collating available data that reported on POPs in Ghana.2) Identify spatial and temporal POP trends in Ghana, and establish potential health risks3) Quantify background concentrations of dioxins and DLCs in sera of primiparous Ghanaians, and in breastmilk of Ghanaian lactating mothers, in addition to infant dietary exposure to dioxins and DLCs in breastmilk.The dissertation is divided into two main sections: The first part presents a comprehensive and systematic review on the Stockholm POPs previously studied in Ghana to date. The second part focuses on the use of modified analytical sample preparation methods and instrumentations to determine background concentrations of dioxins and DLCs in Ghanaian human tissues, using gas chromatography with atmospheric pressure chemical ionization-tandem mass spectrometry (GC-APCI-MS/MS) in Ghanaian human tissues. The first part of this work entails a systematic and comprehensive review of data on sample collection, preparation and analytical methods from previous studies undertaken on the Stockholm POPs in Ghana, since 2001. A review was conducted on POPs in different matrices: environmental and humans, a comparison of concentration against relevant health criteria, and a discussion on spatial and temporal trends. The purposes of this work were to determine whether POPs were increasing or decreasing in the Ghanaian environment, and to ascertain knowledge gaps in data, as the focus has heavily been on the environment, with limited/sporadic studies in humans. This review identified a need to assess exposures to toxic classes of POPs in vulnerable populations, including lactating mothers, pregnant women, and occupationally exposed workers. Results obtained from data analyses of previous studies showed concentrations in excess of United States Environmental Protection Agency (USEPA) regulatory standards for per- and poly-fluoroalkyl sulphonates (PFASs) and dichlorodiphenyldichloroethane (DDD) in water, polychlorinated and polybrominated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs and PBDD/Fs) in e-waste soils, and polybrominated diphenyl ethers (PBDEs) in aquatic organisms and dairy products. The published studies do not cover major regions nationwide. The inconsistency in methods and analytes measured, along with data scarcity in some regions, makes it challenging to identify temporal trends. However, decreasing concentrations of some legacy POPs in soil/sediment and aquatic organisms, with increasing concentrations of some POPs were reported in water, fish, fruits and vegetables. Studies that performed health risk assessments were limited although environmental and human data indicated elevated health risks to e-waste workers, some farmers and vulnerable sub-populations. This review identified potential human health risks from POPs in the Ghanaian environment and the need for more consistent and widespread monitoring program. Following recommendations from the first part of this research, the second part focuses on assessing Ghanaian human exposure to some of the toxic classes of POPs including dioxins and DLCs. An analytical sample separation method was developed that can be used for determination of low, background concentrations of dioxins and DLCs in human serum and breastmilk. Previously established methods utilized multiple fractionation steps and clean-up procedures on expensive equipment, such as the Power-prep sample clean-up instrument. Thus, a manual sample extraction and clean-up method for analysis of low level DLCs in breastmilk and serum was developed for application in developing. The target analytes included detection of 17 congeners of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), 12 congeners of 8 mono-ortho and 4 non-ortho coplanar or dioxin-like PCBs (dlPCBs), 7 congeners of polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs), and 7 congeners of mixed halogenated dibenzo-p-dioxins and furans (PXDD/Fs, where X=Br or Cl). Method validation was completed on the National Institute of Standards and Technology (NIST) Standard Reference Material 1958 (NIST 1958) serum samples. The analytical method provided for low limits of detection (LODs) in the femtogram levels (fg), with analytes recoveries ranging between 41.8-129.9 % for the classes of POPs studied (dlPCBs, PCDD/Fs, PBDD/Fs and PXDD/Fs) in both serum and breastmilk samples.The method was applied to 34 sera from primiparous Ghanaians, and 24 breastmilk samples from first-time lactating mothers. Samples were collected in April 2017 in two municipalities in Ghana: Accra and Tema, both in the Greater Accra region. Based on health risks associated with dioxins and DLCs, the impact of maternal body burdens on foetal exposure is significant. Similarly, the impact of dioxin exposure on infants from breastmilk of lactating mothers is also considered to be significant. Questionnaire data from participants was used to explore contributions from environmental and dietary exposures using questionnaire data. For serum samples, the calculated average toxic equivalent concentration (TEQ) was 5.3 pg TEQ/g lipid weight (lw), with contributions from dlPCBs (1.25 pg TEQ/g lw), PCDD/Fs (3.10 pg TEQ/g lw), PBDD/Fs (0.49 pg TEQ/g lw) and PXDD/Fs (0.50 pg TEQ/g lw). The total TEQ concentration was lower than background TEQ concentrations reported in sera of pregnant women globally; however, the body burdens indicate that dioxins and DLCs are retained in serum, and can be transferred from mother to foetus transplacentally. Positive correlations were obtained for total serum dioxins and DLC concentrations with age and Body Mass Index (BMI). Dietary intake of seafood and dairy products had a strong influence on PCDD/F and dlPCB concentrations. Statistically significant differences were observed for serum dioxins and DLCs in participants from Accra (in close proximity to Agbobloshie e-waste site) and Tema. Given the significant TEQ contribution of PBDD/Fs and PXDD/Fs (~20%), it is essential to explore these classes of dioxins and DLCs in future biomonitoring studies as they may pose health risks, and add extra diagnostic information in source exposure investigation. In the second study, an examination of toxic mixed halogenated dibenzo-p-dioxins and furans (PXDD/Fs, where X= Br or Cl), and dioxin-like polychlorinated biphenyls (dlPCBs) was undertaken in breastmilk samples in 24 first-time lactating mothers from Greater Accra region in Ghana. The mean concentrations in breast milk samples ranged from 0.15-212.9 pg/g lipid for dlPCBs (mean TEQ: 1.67 pg TEQ/g) was similar to 1.25 pg WHO2005-TEQ/g lipid. Lesser mean concentrations for 2,3,7,8-PXDD/Fs (and PBDD/Fs) ranged between <0.01-1.67 pg/g lw, with a tentative total mean TEQ of 0.56 pg TEQ/g lw- this was similar to 0.5 pg TEQ/g lw detected in srum. For nursing infants, the average estimated daily intake of dlPCBs in infants from 21 breastmilk samples was 4.95 pg TEQ/kg bw/day; contributions from PXDD/Fs and PBDD/Fs resulted in an average estimated daily intake of 6.54 pg TEQ/kg bw/day. The results obtained, although lower than infant dietary intake estimates in breastmilk from industrialized countries, exceed the recommended safety standards of 1 pg TEQ/kg bw/day and 1-4 pg TEQ/kg bw/day. Future work on occupationally exposed individuals such as firefighters and e-waste workers in Ghana will be pursued using the methods to understand how dioxins and DLCs accumulation patterns differ in humans based on their occupational source of exposure. Further, the complementary use of non-targeted analysis will be explored in order to identify the suite of toxic contaminants in sera of occupationally exposed individuals.