WHO- and UNEP-Coordinated Exposure Studies 2000–2019: Findings of Polychlorinated Naphthalenes

Abstract

The concentrations of polychlorinated naphthalenes (PCN) were determined in 40 pooled human milk samples from 39 countries covering all five of the United Nations regional groups. The samples were collected in the 2016–2019 exposure studies on persistent organic pollutants coordinated by the United Nations Environment Programme (UNEP).The median concentration of the sum of 26 PCN was 55 pg/g lipid (range 27 pg/g to 170 pg/g). Human milk from European countries showed considerably higher levels than those found in milk from countries in the African, Asia-Pacific, and Latin America/Caribbean regions. The most abundant congeners were the congener pairs PCN 52/60 and PCN 66/67 (inseparable by conventional chromatography) and to a lesser extent PCN 28/36, PCN 42, PCN 46, PCN 48, PCN 59, and PCN 69.Among other adverse biological effects, a critical response of many PCN congeners is dioxin-like toxicity. So, in addition to reporting concentrations of individual congeners, the toxic equivalents (TEQ) were also calculated in these samples, using two sets of relative effect potency (REP) values: a set that has been used in a number of human exposure studies and another set reported by Falandysz et al. (J Environ Sci Health, Part C: Environ Carcinogenesis Ecotoxicol Rev 32(3):239–272, 2014). The median PCN-TEQ concentration in human milk was 0.07 pg PCN-TEQ/g lipid (range 0.03 pg/g to 0.23 pg/g), when calculated using the human biomonitoring study REPs, and 0.03 pg PCN-TEQ/g lipid (range 0.01 pg/g to 0.10 pg/g), when calculated with other suggested REPs. The vast majority, about 90%, of this TEQ can be attributed to the PCN 66/67 congener pair. Individual REPs for PCN 66 and 67 from in vivo studies are quite different, but a chromatographic separation of these two congeners is not possible under routine GC conditions. Different approaches to estimate the uncertainties showed that the value of the REPs used is more important than the analytical problem to separate PCN 66 and PCN 67. PCN-TEQ based on the two sets of REPs differ approximately by a factor of 2.2, whereas the congener-specific determination was estimated to result in approximately 30% lower concentrations in comparison with the standard method.The assessment of PCN 66 and PCN 67 in order to obtain confirmed TEF would be most important for calculations of the dioxin-like toxicity of PCN, followed by PCN 69. Minor contributions to PCN-TEQ concentrations in human milk come from PCN 52/60, PCN 64/68, PCN 70, and PCN 73.On average, the contribution of PCN-TEQ to the cumulative TEQ (including the overall sum of toxic equivalents of PCDD, PCDF, and dioxin-like PCB [WHO2005-TEQ]) is between 1% and 2%, with a wider range of up to 5% for the 39 countries of this study. This is about an order of magnitude lower than the contribution of dioxin-like PCB to the cumulative TEQ (median 26%). In line with the observed higher total PCN concentrations, European countries also showed considerably higher levels of PCN-TEQ than found in the other regions. PCN-TEQ calculated with REPs used in human biomonitoring studies add on average about 2% to the cumulative TEQ of dioxin-like contaminants in Africa, the Asia-Pacific region, and Latin American and Caribbean countries and about 4% in European countries. The corresponding contribution of PCN-TEQ calculated using the other set would be 1% in non-European countries and 2% in European countries.

Risks for animal and human health related to the presence of polychlorinated naphthalenes (PCNs) in feed and food

“…For the exposure assessment of breastfed infants, an age of 3 months was selected, corresponding to a weight of about 6.1 kg, and an estimated average daily consumption of 800 mL and a high consumption of 1200 mL of human milk (EFSA Scientific Committee, 2017a). The occurrence data were taken from European pooled milk samples that were collected and analysed as part of the WHO/United Nations Environment Programme (UNEP)‐coordinated human milk studies from 2000 to 2019 (Tschiggfrei et al., 2023). The two different exposure scenarios were calculated, including the exposure assessment via human milk of PCN‐66/67 and of the mixture of PCN congeners (the mixture scenario A and B; see Section 3.3.3).…”

“…Concentrations of PCNs in human milk were found to be two to three times higher in European samples when compared to other global regions in a study conducted by the UNEP/WHO (notable exceptions were noted in Salomon Islands and Jamaica) (Tschiggfrei et al., 2023).…”

“…Overall, the exposure estimates between calculated for the mixture scenario are approximately 20% higher than the exposure estimates obtained for the individual PCN-66/67 that indicates a major contribution of the PCN-66/67 to the overall exposure of the mixture of the selected PCN congeners. T A B L E 2 0 Occurrence levels (ng/kg) in pooled human milk samples from European countries collected and analysed in 2016 and 2019 within the WHO/UNEP field study (Tschiggfrei et al, 2023). No data was available for infant formula, and only one sample on follow-on formula was available in the database.…”

“…PCNs were included in this study for the period 2000–2019 (Tschiggfrei et al., 2023). There were five rounds of this study conducted over the period with the number of participating countries as follows: 2000–2003 (26); 2004–2007 (13); 2008–2011 (45); 2012–2015 (17) and 2016–2019 (42).…”

“…Several PCN congeners including some reported to be of most toxic and bioaccumulative significance like, PCNs 27, 28, 30, 31, 34, 35, 37, 38, 40, 43, 45 and 48, 55, 59 and 60, 64, 66, 67, 68, 71 and 72, co‐elute under routine analysis conditions (HRGC), and determination of their individual concentration in foods and any other materials under routine conditions in practice is not possible (Falandysz et al., 2008; Horii et al., 2004; Tschiggfrei et al., 2023). The development of GC columns for research purposes allows for the separation of PCNs 66 and 67 in Halowax 1014 and in air, but these have not been found to be suitable for the analysis of foods, and data have not been reported for the analysis of foods and biological or environmental samples using such columns (Helm et al., 1999).…”