Polychlorinated Naphthalenes and Other Organochlorine Contaminants in Swedish Human Milk, 1972–1992

Abstract

The concentrations of polychlorinated naphthalenes (PCNs) were determined together with polychlorinated biphenyls (PCBs), dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), 1,1-bis-(4-chlorophenyl)-2,2,2-trichloroethane (p,p'-DDT), 2,2-bis(4-chlorophenyl)-1,1-dichloroethylene (p,p'-DDE) and hexachlorobenzene (HCB) in milk, sampled in the course of 1972-92 from mothers living in Stockholm. A previously developed method for multicomponent analysis of organochlorine environmental contaminants was adapted for simultaneous analysis of PCNs. The mean recoveries of seven chlorinated naphthalene (CN) congeners added to milk prior to extraction were 76-99%. Similar recoveries were obtained for the commercial PCN product Halowax 1014. The pattern of PCNs in milk differed to a great extent from that in the commercial PCN products. The dominating congeners in breast milk were 1,2,3,5,7-pentachloronaphthalene (CN-52), 1,2,3,4,6,7- and/or 1,2,3,5,6,7-hexachloronaphthalene (CN-66/ CN-67) and one unidentified tetrachloronaphthalene. There was a notable decrease in the concentrations of PCNs as was of the other organochlorine contaminants in milk from 1972 to 1992. During this time period the sum of CN congeners decreased from 3,081 to 483 pg/g milk fat and the sum of toxic equivalents of dioxin and dioxin-like compounds decreased from 100 to 39 pg/g milk fat.

The effect of exposure route on the distribution and excretion of hexachloronaphthalene in rats

“…Polychlorinated naphthalenes have been detected in human adipose tissue samples [1,24,36,37], liver [24], blood [38,39] and breast milk [26,40,41] of the general population. The PCN congener/isomer pattern found in human samples was significantly different from that in the commercial PCN mixtures [1].…”

“…The PCN congener/isomer pattern found in human samples was significantly different from that in the commercial PCN mixtures [1]. The dominating congeners in almost all human specimens examined were two penta-and two hexa-isomers, namely 1,2,3,5,7/1,2,4,6,7-pentachloronaphthalene and 1,2,3,4,6,7/1,2,3,5,6,7-hexachloronaphthalene [24,26,30,36,37,39]. Toxicological symptoms induced by PCNs are very similar to those caused by polychlorodibenzodioxins (PCDDs) [27,28].…”

“…General population studies carried out in different regions of the globe have revealed the highest concentrations of PCNs (mostly pentaand hexachloronaphthalene isomers) in liver and adipose tissue [1,4,24,25]. The Swedish studies performed in 1972-1992 revealed the presence of these compounds (including mainly 1,2,3,5,6,7-HxCN) in breast milk, which may be particularly dangerous to the developing infants [26], mostly because the elimination of compounds like PCNs and their lipophilic metabolites from body fat is very slow [1]. The literature review shows that data on the disposition of single PCN congeners in the rat body, including …”

Chemical contaminants in breast milk: time trends and regional variability.

“…Dioxins and furans have been measured in the breast milk of women from at least 35 countries, including Albania, Cambodia, Croatia, Estonia, the Faeroe Islands, India, Jordan, New Zealand, Pakistan, South Africa, Thailand, Vietnam, most European countries, and the United States (12,13,28,(69)(70)(71)(72)(73)(74)(75)(76)(77)(78)(79). The general time trend in many countries seems to be toward a slight decrease of dioxin levels in breast milk over the past decade (3).…”

“…Extensive data from Sweden ( Figure 8) shows a downward trend in average breast milk levels over 25 years, with a relatively steep decline from the 1970s to the mid-1980s and evidence of a plateau since the mid-1980s (28,74). In many other countries, it has been difficult to make a national assessment of whether levels are going down because of regional variations.…”