Health effects in the Arctic
In a Northern Norwegian study on pregnant and delivering women (The MISA study, n=516), low maternal concentrations of both organochlorines (OCs) and toxic elements, and normal levels of essential elements, were observed. The concentrations of OCs and the non-essential (toxic) and essential elements appeared to be driven by the physiological adaptations during pregnancy. A comparative Vietnamese study demonstrated relatively high levels of p,p'-DDE and p,p'-DDT, among the highest globally and possibly reflecting recent or current use. In contrast, the concentrations of PCBs were slightly lower than those found among the Norwegian mothers. Place of living was associated with the observed OC concentrations for the Vietnamese participants, and Sámi ethnicity for elements in the Northern Norwegian survey; probably due to different dietary patterns. Diet as a source was only assessed for the toxic and essential elements. Fish consumption was found to be a strong predictor for arsenic, mercury and selenium. Although not investigated in detail, fish and seafood intake can also be an important contributor to serum or plasma OC levels. The lower PCB concentrations observed in Vietnam in combination with published suggestions of higher fish intake suggest the consumption of smaller, younger, and lean fish species in combination with low environmental deposition by long-range transport and minor local sources.
In a study of POPs in Norwegian men from 1979 to 2007 (Nost et al., 2013), substantial declines were observed for all POPs, see figure below, with the exception of chlordanes (e.g., t-Nonachlor). Overall, decreases were observed from 1979 in concentrations of most pentachlorinated PCBs (PCB 99, 101, 105, 118, and 123) and hexachlorinated PCBs (PCB 128, 141, 149, 153, and 167). Concentrations of heptachlorinated PCBs (PCB 170, 180, 187, and 194) initially increased from 1979 to 1986, and declined in subsequent years. Overall, findings suggested that POP concentrations decreased during 1979-2007 in men from Northern Norway and average summed POP concentrations in 2007 were one third of concentrations measured in 1979. Peak PCB153 concentrations were measured in 1979 and 1986 confirming this period as the years of highest human exposure. The downward trends in serum concentrations likely reflect declining environmental concentrations due to reduced emissions during the same time period. This is in accordance with previous findings for environmental and human POP concentrations in Europe (AMAP 1998; Bignert et al. 1998). The findings indicate that serum concentrations of DDTs peaked before PCBs, which is consistent with emission estimates for DDTs (Li and Macdonald 2005) and PCBs (Breivik et al. 2010). The delay in global emissions of PCBs could be due to the long lifetime of PCB-containing products (e.g. transformers, capacitors) (Breivik et al. 2007). The findings suggested that regulatory measures to reduce the manufacture and use of POPs during the 1970s and 1980s had rapid impacts not only on environmental concentrations (AMAP 1998), but also on human exposures.
From Northern Finland 1966 Birth Cohort (NFBC 1966) biological bank, 250 blood samples (127 male and 123 female) were selected for the analysis of mercury, arsenic, cadmium and lead (Abass et al., manuscript.). The selection criteria were based on individual persons born and living last 5 years in the Eastern and Western part of Lapland. The aim of this study was to assess these toxic elements in population in Lapland, and to compare the results with European and other populations. The concentration of mercury ranged from 0.23 to 14.54 µg/L, with the median value being 2.06 µg/L. Arsenic ranged from 0.15 to 18.02 µg/L, with a median value of 0.53 µg/L. Cadmium ranged from 0.11 to 4.03 µg/L, with a median value of 0.49 while lead ranged from 2.06 to 145.5 µg/L, with a median value of 13.6 µg/L. Compared to the guideline values established by international organizations, 21 percent, 0 percent, 0 percent and 2 percent of the Lapland population had higher levels of Hg, As, Cd and Pb, respectively. Significant correlations between mercury and fish consumption (0.424) as well as between cadmium and smoking (0.368) were also confirmed.
As seen from the academic performance of schoolchildren, there is an indication of the possibility of a known adverse effect of PCBs on the neuro-psychological development of children (ATSDR, 2007); these effects in children from the villages where rehabilitation activities had been carried out apparently were somewhat less, according to the median estimate of their knowledge in elementary school. For example, in a cohort of children for which the concentrations of PCBs in their blood at birth was less than 1 mg/L, the average school performance was 5 percent to 7 percent higher than in children with PCB concentrations at birth greater than 1 μg/L. If we compare a cohort of children living in villages where rehabilitation activities were carried out, the average of their performance in primary school was approximately 10 percent higher than children in the villages where such activities were not conducted.
Although these differences did not reach an acceptable level of statistical significance, owing to the limited cohort of children who participated in the pilot project, these data support our estimates of a positive development of PCB trends in humans.
There are no human health cohorts from Greenland included in the ArcRisk project. However, the recently finished CLEAR project have made some conclusions; these include:
- the direct physical effects of climate change on human contamination level are likely to be minimal compared to lifestyle changes and changes in food webs;
- environmental chemicals at the present exposure levels are likely to have only limited effects on male reproductive function;
- possible effects on female reproductive function, childhood growth and development and gene-environment interactions have not yet been evaluated.
A study with the aim to extrapolate body burden and exposure to the whole lifespan of the population, by a one-compartment toxicokinetic model, was conducted within the ArcRisk project. In this study PCB153-associated human health effects and risks were assessed by using data obtained from the AMAP biomonitoring programme, in Inuit women covering the years 1994–2006 (Disko Bay) and 1999–2005 (Nuuk) in Greenland, and 1992–2007 (Nunavik) in Canada. By using risk characterization modelling, calculated Hazard Quotients were higher than 1 between the years 1955 and 1987 for the 90th population percentile and during 1956–1984 for the 50th population percentile. Cancer risk for overall exposure of PCB153 ranged from 4.6×10−5 to 1.8×10−6 for the 90th percentile and 3.6×10−5 to
1.4×10−10 for the 50th percentile between 1930 and 2049 , when central estimates or upper-bound slope factors were applied. Cancer risk was below 1×10−6 for the same time period when a lower slope factor was applied. Significant future research requirements to improve health risk characterization include, among others, larger sample sizes, better analytical accuracy, fewer assumptions in exposure assessment, and consequently, a better choice of the toxicity benchmark used to develop the hazard quotient.