PCDD/F and PCB occurrence data
I-TEq and PCB-TEq concentrations for rainbow trouts, 0.74 pg g-1 w.w. and 1.5 pg g-1, respectively, were moderate when one considers that rainbow trout is a fatty fish. Two explanations can be provided for the low concentrations (1) all rainbow trouts were very young (2 years of age) and (2) they were all farmed trouts and they had been fed with artificial fodder. Two-year-old trouts were chosen for the study because this is the age farmed trouts are normally harvested.
A decline of 50% was observed from 1.8 in 1993 (Hallikainen et al. 1995) to 0.74, in the I-TEq concentration of rainbow trout samples in Finland. This current value is now in the same range as the concentration of rainbow trout in Germany (Malisch 1998).
In cows' milk from 1991 (Vartiainen and Hallikainen 1994) to 1998 the decline in concentration of I-TEq was from 0.99 to 0.12 pg I-TEq g-1 fat. In Germany and The Netherlands, the concentrations in cow's milk were six to 10 times higher than in Finland, respectively (Liem and Theelen 1997, Malisch 1998). The concentrations may have declined in cows' milk in Finland due to the decrease in deposition of PCDD/Fs onto grassland from the atmosphere.
Similarly to cows' milk, concentration of I-TEq also in eggs has declined during the 1990s from 1.6 to 0.52 pg I-TEq g-1 fat. In Germany and The Netherlands, the concentrations in eggs were three to four times higher than in Finland (Liem and Theelen 1997, Malisch 1998).
Table 4. Daily consumption of food and food groups, and concentrations and intakes of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and polychlorinated biphenyls (PCBs) as toxic equivalents (TEqs) in Finland.
Food group Consumption, g day-1
I-TEq concentrations in pork have decreased from the 1991 value of 0.29 (Vartiainen and Hallikainen 1994) to 0.051 pg I-TEq g-1 fat. The opposite situation was discovered with beef, where the values increased from 0.018 to 0.29 pg I-TEq g-1 fat. In Germany and The Netherlands, the concentrations in pork and beef were two to 10 times higher than those found in Finland (Liem and Theelen 1997, Malisch 1998). It was very difficult to detect any time trend in these figures in Finland. Both values are low probably because pigs as well as beef cattle are slaughtered when they are still very young.
The concentrations of I-TEqs and PCB-TEqs in flour, potato and vegetable samples were both virtually negligible and their impact on intake was very small. It is very difficult to compare the concentrations of vegetables between different countries because of the heterogenity of the measured items in each country. The measured concentrations in Finland were very low when compared to Spain or Germany (Malisch 1998, Domingo et al. 1999). Only the I-TEq concentration of leafy vegetables, 0.01 pg g-1 w.w., was in the same range as reported in the study from Germany (Malisch 1998).
Intake of PCDD/Fs and PCBs
The intake of PCDD/Fs declined from 95 pg N-TEq (Hallikainen et al. 1995) to 46 pg I-TEq between 1992 and 1999 (N-I-TEq and I-I-TEq toxic equivalency factors are almost identical).
Two obvious reasons for this decline were found. First, the lower concentrations of I-TEqs in cows' milk and eggs. Second, the consumption of eggs, fish and milk has also diminished compared to the previous dietary survey.
To estimate the impact of new occurrence and new consumption data to the intake of PCDD/Fs, the intake of PCDD/Fs was calculated with new concentrations of PCDD/Fs combined with the old food consumption data. With this kind of procedure, the intake was calculated to be 70 pg I-TEq day-1. It is concluded that the changes in consumption data and concentrations have both affected almost equally the intake of PCDD/Fs.
The intake of PCB-TEqs, 53 pg PCB-TEq day-1, was clearly underestimated in this study because PCB-TEq concentration data for Baltic herring were incomplete. The total intake of TEqs was 100 pg TEq day-1 (1.3 pg TEq kg-1 b.w. day-1), which is in the range of the tolerable daily intake (TDI), 1-4 pg TEq kg-1 b.w. day-1, given by WHO (van den Berg et al. 1998).
The average intake of PCDD/Fs in Europe has been reported to be between 42 and 210 pg I-TEq day-1 (Liem and Theelen 1997, Becher et al. 1998, Harrison et al. 1998, Malisch 1998, Domingo et al. 1999, Zanotto et al. 1999). Both the lowest and the highest intakes have been measured in the Mediterranean around Venice, Italy (42 pg I-TEq day-1) and in Spain (210 pg I-TEq day-1) (Domingo et al. 1999, Zanotto et al. 1999). In Western Europe (The Netherlands, Germany, UK), the intake has been calculated to vary between 61 and 90 pg I-TEq day-1 (Liem and Theelen 1997, Harrison et al. 1998, Malisch 1998). In the northern parts of Europe in addition to Finland, there is a current estimation available for the daily intake of PCDD/Fs for Norway where it varied between 50.6 and 84.6 pg I-TEq day-1 (Becher et al. 1998). The PCDD/F intake in the USA was estimated to be 41 pg TEq day-1 (US EPA 2000). In Japan, the estimated
intake of PCDD/Fs was equivalent to European intakes, ~70 pg I-TEq day-1 (Yoshida et al.
2000). The lowest intake of PCDD/Fs has been reported from New Zealand, 14.5 pg I-TEq day-1 for the average population (Buckland et al. 1998).
The recent PCB-TEq intake estimations are available from UK, USA, Norway and New Zealand. The lowest intake for PCB-TEqs was also found in New Zealand, 12.2 PCB-TEqs day
-1, followed by the USA (24 PCB-TEqs), UK (54 PCB-TEqs) and Norway, where the intake was estimated to be between 137 and 190 pg PCB-TEq day-1.
Time trends of PCDD/F intake have been studied in the UK, The Netherlands and Germany (Liem and Theelen 1997, Harrison et al. 1998, Malisch 1998). The trends for the intakes have been declining in all of these studies. In the UK, the intake of PCDD/Fs between 1982 and 1992 decreased from 4.1 to 1.5 pg I-TEq kg-1 b.w. day-1. Simultaneously, the daily intake of PCB-TEq also declined from 2.7 to 0.9 pg PCB-TEq kg-1 b.w. (Harrison et al. 1998). A decline of almost 40% in the intake of PCDD/Fs was observed in The Netherlands between 1991 and 1997, when the daily intake decreased from 115 to 73 pg I-TEq (Liem and Theelen 1997). In Germany, the time trend results showed that the intake in 1993-96 was about one-half of the intake calculated between 1986 and 1991, from 127 to 61 pg I-TEq day-1 (1.82-0.88 pg I-TEq kg
-1 b.w. day-1) (Malisch 1998).
The contribution of fish in Finland increased from 60 to 82%, indicating that fish is clearly the most important contributor to PCDD/F intake in Finland. In the dietary method used in the FINDIET 1997 survey, the fish consumption can be estimated lower than by other dietary methods and this further emphasizes the impact of fish to the intake. The contribution of milk and dairy products had clearly diminished, from 31 to 8% because of the decreased I-TEq concentration and reduced consumption.
In the Venetian and Norwegian studies, fish and fish products contributed to the PCDD/F intakes as much as in the Finnish study. In Venice, the proportion varied from 42 to 50% and in Norway from 28 to 43% (Becher et al. 1998, Zanotto et al. 1999). In the UK, Germany, The Netherlands, the USA and New Zealand the main source of PCDD/Fs are meat and meat products and milk and dairy products, the proportion of both groups being ~30% (Liem and Theelen 1997, Buckland et al. 1998, Harrison et al. 1998, Malisch 1998, US EPA 2000). The proportion of fish and fish products in these countries varied between 1 and 20%. The impact of vegetables on the intakes of PCDD/Fs have been considered as negligible or insignificant in many studies, but recently in Spain the contribution of vegetables has been estimated as being noteworthy (Domingo et al. 1999). Taking the impact of vegetables into consideration in the intake calculations, Domingo et al. concluded the intake in Catalonia to be 210 pg I-TEq day-1. If
one excluded vegetables from the calculations, then the intake would have been 117 pg I-TEq day-1. Lovett et al. (1997) concluded that the increase in intake of PCBs and PCDD/Fs resulting from eating fruits and vegetables was unlikely to >3% for PCBs and 8% for PCDD/Fs, of the average daily intakes of these contaminants from all food sources.
Table 5 shows the percentage exposure for PCDD/F from the most important food sources, and daily intake of PCDD/Fs in different countries. It reveals that geographically the countries nearest to Finland i.e. Germany and Norway, have the most similar intakes as Finland, 61.3 and 51 pg TEq day-1, respectively. The Western European countries, The Netherlands and UK can be grouped with each other with 73 and 90 pg TEq day-1 intakes. The daily intake of PCDD/Fs in Finland was ~3 times higher than the intakes in New Zealand (14.5 pg I-TEq).
In this study, the TEq intakes have been calculated with the concentration results where the non-detected results were considered as zeros. If the intakes of PCDD/Fs and PCBs were calculated with these results replaced by LODs, the PCDD/F intake would be 65 pg I-TEq day-1 and PCB intake 54 pg PCB-TEq day-1. This shows the crucial effect of handling the non-detected values when the concentrations of studied substances are very near to the limit of determination (LOD).