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Exposure related observations in humans: other data

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Administrative data

Endpoint:
exposure-related observations in humans: other data
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2005
Reliability:
1 (reliable without restriction)

Data source

Reference
Reference Type:
publication
Title:
Determination of Dechlorane Plus in Serum from Electronics Dismantling Workers in South China
Author:
G. Ren, Z. Yu, S. Ma, H. Li, P. Peng, G. Sheng and J. Fu
Year:
2009
Bibliographic source:
Environ. Sci. Technol. 2009 43. 9453-9457
Report Date:
2009

Materials and methods

Type of study / information:
Dechlorane Plus concentrations in human blood plasma of exposed workers.
Endpoint addressed:
not applicable
Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
Blood plasma levels of Dechlorane plus were analyzed in two cohorts of 20 volunteers each. Blood samples were analyzed by means of GC-MS.
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
not specified
Details on test material:
Individual solutions of the syn- and anti-isomers (50 µg/mL, in toluene, purity: >95%) used for calibration and as reference substance were purchased from Wellington Laboratories (Guelph, ON, Canada).

Method

Ethical approval:
confirmed, but no further information available
Details on study design:
Serum Samples: Serum samples were collected from residents at two sites in 2005. The first cohort consisted of 20 residents from an e-waste dismantling region, Guiyu town, Shantou City, Guangdong Province. Eighty percent of the families in Guiyu town were engaged in recycling work using primitive methods (including chipping and melting plastics without proper ventilation, burning coated wire to recover copper, removing electronic components from printed circuit boards, and burning unsalvageable materials in the open air). The second cohort consisted of 20 residents of Haojiang district, Shantou City, Guangdong Province, about 50 km east of Guiyu, where fishing was the predominant industry.
Before sampling, all participants were informed of the procedure and provided signed consent. Blood samples were taken from each volunteer by medical professionals using BD Vacutainerserum tubes (with clotting agent and polymer separator). Samples were then centrifuged, immediately frozen, and kept at -20 °C until analysis. The volunteers ages ranged from 23 to 67 years, and 73% were male (27% female).
Sample Cleanup and Analysis: Surrogate standards (PCB-209 and 4-H0-PCB-72) were first added to the sera (5 g) in a Teflon separating funnel and denatured using hydrochloric acid and propan-2-ol. The samples were then extracted three times with hexane/MTBE (1:1). After combining the extracts, the phenolic and neutral compounds were separated using an aqueous solution of potassium hydroxide (0.5 M in 50% ethanol). The neutral fractions were treated with concentrated sulfuric acid, followed by a sulfuric acid-impregnated silica gel column (silica/sulfuric acid 2:1 w/w; 1 g). DP and BDE-209 were eluted with 8 ml of hexane followed by 10 ml of hexane/dichloromethane (1:1, vol/vol). The final extracts were concentrated to 20 µL under a gentle nitrogen stream, and a known amount of internal standard (13C-PCB 208) was added before injection.
The phenolic fractions were derivatized with an excess of diazomethane solution at room temperature for one night, then further cleaned with sulfuric acid-impregnated silica gel (silica/sulfuric acid 2:1 w/w; 1 g] using 12 mL of hexane/dichloromethane (1 :1, vol/vol) as the eluent. The final extracts were concentrated to 20 µL under a gentle nitrogen stream and a known amount of internal standard (13C-PCB 208] was added before injection.
Samples were analysed for the two DP isomers and BDE-209 using an Agilent 7590 series gas chromatograph coupled to an Agilent 5975C mass spectrometer (GC/MS) using negative chemical ionization (ECNI) in the selected ion monitoring (SIM) mode. Manual injection (1 µl) was made in the pulse splitless mode with a purge time of 2.0 min. The injection port and the GC to MS transfer line were held at 280 and 290 °C, respectively. A 15-m DB-5-HT MS column (250 µm i.d., 0.25- µm film thickness; J&W Scientific, Folsom, CA) was used for DP analysis. The GC oven temperature program was as follows: held at 110 °C for 5 min, 20 °C/min to 200 °C, held for 4.5 min, and then 7.5 °C/min to 300 °C, and held for 16 min. The following ions were monitored: m/z 475.7 and 473.7 for the internal standard 13C-PCB-208, m/z 498 and 500 for PCB-209, m/z 653.7 and 651.7 for DP, m/z 619.7, 617.7, 583.7 and 585.7 for the dechlorination metabolites of DP, m/z 79, 81, 486.7, and 488.7 for BDE-209.
QA/QC: The peaks were identified and quantified only if the GC retention times matched those of the standard compounds to within 0.1 min, the signal-to-noise ratio was >5, and the isotope ratio between the two monitored ions was within 15% of the standard value. DP was analysed using 13C-PCB208 as an internal standard. Since there was no obvious difference in extraction efficiencies between DP and the lesser chlorinated PCB, we used recovery of the PCB surrogate as an indicator of DP recovery. The spiked PCB recoveries averaged 91 - 108%. Laboratory blanks, using fetal bovine serum, were treated and analysed in the same way as the regular samples and constituted about 20% of the total samples analysed. The DP concentrations in the blank samples were undetectable or <1% of the average value. Concentrations were not blank- or recovery-corrected.
Statistical Analysis: The concentrations of all target compounds were reported on a lipid weight basis. Statistical analysis was performed using SPSS 15.0 software. Statistical significance was defined as p < 0.05.
Exposure assessment:
measured
Details on exposure:
The first cohort consisted of 20 residents from an e-waste dismantling region, Guiyu town, Shantou City, Guangdong Province. Eighty percent of the families in Guiyu town were engaged in recycling work using primitive methods (including chipping and melting plastics without proper ventilation, burning coated wire to recover copper, removing electronic components from printed circuit boards, and burning unsalvageable materials in the open air). The second cohort consisted of 20 residents of Haojiang district, Shantou City, Guangdong Province, about 50 km east of Guiyu, where fishing was the predominant industry.

Results and discussion

Results:
Using purified analytical solutions of individual isomers as standards, we determined the serum DP concentrations from residents of Guiyu and Haojiang. A pooled serum sample from the reference population from Guangzhou, a typical urban city in South China, was also included for DP screening analysis. DP isomers were detected in the pooled sample, but the concentration was below the limit of quantitation.
Table 1 (see below) summarizes the serum levels of DP in residents of Guiyu and Haojiang. DP was detected in all serum samples. The sum of the serum concentrations of the anti- and syn-isomers (Sum of DP) ranged from 7.8 – 465 ng/g lipid (median: 42.6 ng/g) and 0.93 - 50.5 ng/g lipid (median: 13.7 ng/g) for Guiyu and Haojiang, respectively. The median concentration of Sum of DP was three times higher in Guiyu than in Haojiang, consistent with the expected elevated exposure due to dismantling of e-waste products. The maximum serum DP concentration in Guiyu was 465 ng/g lipid. This is the highest reported concentration so far reported from biota or human samples.
Serum Sum of DP concentrations were not correlated with age in either the Guiyu or Haojiang samples. However, a previous study on serum PBDE levels in this region did find a positive correlation with age (significant at the 95% level) in Haojiang, though no correlation in Guiyu. According to the results of the questionnaire, most of the dismantling workers in Guiyu were temporary migrants from other parts of China and had worked there for various lengths of time. It is therefore possible that DP exposure was largely associated with the recent expansion of the e-waste industry in this region (over the past decade), and people of all ages will have been exposed for a similar period of time. The pattern was similar in Haojiang, and it is possible that the heavier DP was transported via air from Guiyu to Haojiang. lt is important to point out that, since the number of participants in this study was relatively small, these associations must be interpreted with caution.

Any other information on results incl. tables

Concentrations of Dechlorane Plus (DP) and different f anti values in Serum Samples from an e-Waste Dismantling Region (Giuyu) and a Nearby Region (Haojiang)

   median     mean     minimum     maximum   
 compound Guiyu Haojiang   Guiyu   Haojiang   Guiyu   Haojiang   Guiyu   Haojiang
 syn-DP 17.1  5.1  16.2  4.3  2.7  0.35  236  17.6
 anti-DP  21.2  8.6  22.5  7.5  5.1  0.54  229  32.9
 f anti  0.53  0.64  0.57  0.63  0.40  0.57  0.77  0.78
 Sum of DP  42.6  13.7  39.8  11.8  7.8  0.93  465  50.5

Possible DP Metabolites: We detected relatively high levels of DP in the electronics dismantling workers, and we therefore hypothesized that DP might produce metabolites in the serum. This is possible because (1) DP has physical and chemical properties similar to some halogenated organic contaminants such as PBDEs and PCBs, and many studies have verified that hydroxylated metabolites of PCBs and PBDEs can be detected in the biota and in serum/milk samples; (2) several in vivo and in vitro studies using liver subcellular fractions have shown that reductive debromination of PBDEs can occur in fish, rats, and birds. Before investigating the presence of DP metabolites in this study, we conducted two control experiments to see if the sample treatment procedures or instrumental analysis produced any metabolites, using individual anti- and syn-DP (1000 ; µg/L). The results showed that no dechlorinated compounds or hydroxy- or MeO-DP were produced as a result of the sample cleanup procedures. To determine if reductive dechlorination or hydroxylated metabolites of DP were formed in humans, several serum samples from electronics dismantling workers were pooled, and the phenolic and neutral fractions were isolated and screened using GC/ECNI-MS. We detected no hydroxylated metabolites in the phenolic extracts, suggesting that no metabolic oxidation occurred, or that any metabolites were below the detection limit. In the neutral fraction, the molecular weight of reductive dechlorinated DP was calculated and the corresponding m/z ion fragment clusters (619.7/617.7) and (585.7/583.7) related to (—Cl + H) and (-2Cl + 2H) species were monitored using SIM mode. A new unidentified peak was found with retention times between those for syn- and anti-DP. To further identify this unknown compound, full-scan mass spectra of this peak were obtained in ECNI mode. The characteristics of the peak were similar to those of DP, except that the molecular ion had a lower 34 amu, which could be due to the loss of a chlorine atom and the addition of a hydrogen atom. The same peak was also reported by Sverko et al. in sediment from the lower Great Lakes. After analysis using high resolution TOFMS, they tentatively identified this peak as a -1 Cl dechlorination product of DP. If the unidentified compound in the pooled serum was the dechlorinated metabolite of anti-DP, it could partially explain the lower variation in f anti values, compared with that in the DP commercial mixture. Another possible explanation for the unknown peak is that DP dechlorination could occur via photolytic or thermal decomposition in the environmental matrix, and then enter the body through ingestion, inhalation, or dermal exposure.

We detected DP in 40 serum samples, and the unidentified peak was present in 19 of the 40 samples (11 of 20 from Guiyu town and 8 of 20 from Haojiang town). Due to a lack of authentic standards, the peak could not be quantified. To our knowledge, this is the first report of the DP dechlorination compound in biota and human samples, but more studies are needed to confirm this result. Further attention should also be paid to this and other dechlorination products in environmental and biomonitoring research. Degradation will alter the physicochemical properties of DP; e.g. the Kow will decrease as the molecular weight decreases. This will in turn affect the environmental fate and transport of DP, leading to changes in its bioaccumulation and toxicological effects.

Applicant's summary and conclusion

Conclusions:
Threefold higher DP concentrations in blood serum of workers in electronic-waste dismanteling industry (in Guiyu) were found compared to a cohort, living and working 50 km away in a fishery dominated area (Haojiang). Total DP levels (syn and anti) of 22.5 and 7.5 ng/g were found as mean values in Guiyu and Haojiang, respectively. F anti values (ratio of anti-DP concentration compared to total DP concentration) were found being significantly lower in Guiyu compared to Haojiang but the reason for this remains unclear, as e-waste is dismanteled by incineration at temperatures exceeding the decomposition temperature of DP. F anti values in Haojiang are similar to f anti values as DP produced.