Increase of Dioxin Blood Levels over the Last 4 Years in the General Population in Spain

To the Editor: It is generally reported that owing to improved emission control of waste incinerators and other industrial sources, levels of dioxins have steadily fallen in Western Europe and the United States. Nevertheless, the attention of public health authorities and the public has focused on dioxins again during the recent outbreak of dioxin-contaminated food and feedstuff in Belgium. A large municipal solid waste incinerator (MSWI) was installed in Mataró, a city located 25 km north of Barcelona. We conducted a study comparing blood levels of dioxins when the plant started functioning in 1995, and 2 years after in 1997. Participants in the study were 104 residents living within 1.5 km from the plant, and 97 residents, matched by age, sex, and socioeconomic status, living at about 4 km from the plant. Subjects were between 18 and 69 years of age in 1995, of both sexes, and were randomly selected from the municipal list of inhabitants. A more-detailed description of this first phase of the study and results has been published. 1 In 1999 we collected one third blood sample and administered the same questionnaire on lifestyle factors and occupation, and repeated dioxin blood measurements in the same individuals of Mataró. We also included a new general population random sample from a similar city, but without any known source of dioxin exposure, located 20 km north of the incinerator. In each phase we pooled the blood samples for the same comparative group of subjects and did a total of 38 analyses. The same World Health Organization accredited laboratory performed all analyses by gas chromatography-mass spectrometry. As shown in Figure 1, our results indicate that a continuous increase of dioxin blood levels took place over the last 4 years. The increase was similar in people living near and far from the incinerator, affecting both sexes and all groups of age. Levels in Mataró in 1999 were similar to those of the group of people living in the comparison city. Both the results of the geographical comparison within Mataró and the comparison with the other city indicate that these increasing levels over time cannot be attributed to this particular incinerator. The current blood levels are around 20 pg international dioxin toxic equivalents (I-TEQ)/g fat. This level is low but still higher than the present levels of about 15 pg I-TEQ/g fat 2 found in the general population of other developed countries. FIGURE 1: Time trends in blood levels of dioxin (I-TEQ ng/kg fat) in residents living in Spain according to residence relative to a municipal incinerator. MSWI = municipal solid-waste incinerator; I-TEQ = international dioxin toxic equivalents.The gradually increasing levels of dioxins in this population sample in Spain is surprising, because a decrease in blood levels has been observed in residents in Germany and other industrialised countries since 1987. 3 A reversal of this trend may have occurred in Germany in 1997–1999, however. 3 Aging of the population may have influenced the observed increase in Spain, although a 40% increase in 4 years cannot be explained solely by aging. Selection bias is not a tenable explanation because our sample consists of identical persons from the general population studied in consecutive time periods. In general populations diet is the most important source of exposure, contributing more than 90% of the daily intake of dioxins. 4 In a study conducted in a city south of Barcelona 5 the total dietary dioxin intake was estimated to be 210 pg I-TEQ/day for a 70 kg person, which is higher than the intake in other European countries. Furthermore, the contribution of dioxin exposure from various food groups differed from that described in northern European countries, with a higher than expected contribution in Spain from cereals, vegetables and fruits, which are traditional components of the Mediterranean diet. The observed increasing trend of dioxins blood levels in the Spanish population, and maybe in Germany, could reflect a recent increase of exposure to dioxins from foods or other unidentified sources. Carlos A. González Manolis Kogevinas Enrique Gadea Guillem Pera Olaf Päpke