Increasing serum levels of non-DDT-derivative organochlorine pesticides in the younger population of the Canary Islands (Spain)

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Abstract

Organochlorine pesticides are a lipophilic class of chemicals that persist in the environment and tend to accumulate in human tissues for years. They came into widespread use in the late 1940s. Because of their capacity to bioaccumulate and biomagnify in food chains and their toxic effects, most of them were banned in industrialized countries, among them Spain, in the late 1970s and 1980s. In 1998 organochlorine pesticides were determined in a representative sample of a Spanish population (around 690 serum samples from people 6 to 75 years old from the Canary Islands). Serum levels of lindane aldrin, dieldrin and endrin, were determined. Our results showed that a high percentage of samples presented detectable levels of some of the organochlorines measured, endrin being the most frequently detected (72%) and at highest concentration (mean 136.7 ng/g fat). Mean concentrations of the main cyclodiene evaluated, dieldrin, was lower to those found in other Western populations. However, serum levels of lindane were higher than those described in North European populations. Influence of geographical and sociodemographic factors was evaluated. Urban populations showed the highest levels of dieldrin, while non-urban population showed the highest serum values of lindane, aldrin and endrin. Unexpectedly, serum values of lindane, aldrin and dieldrin were higher in younger than in older people. Subjects under 18 years showed almost twice as high serum levels of lindane, aldrin and dieldrin than subjects of 65–75 years. These results may well suggest that people living in the Canary Islands have been and are currently exposed to non-DDT-organochlorine pesticides. The type and source of exposure could vary between islands and type of habitat. Contaminated food and/or the environment could be related with this situation.

Introduction

Organochlorine (OC) pesticides are ubiquitous and persist in the environment. They have been measured in environmental and wildlife samples (Covaci et al., 2002, Muckle et al., 2001). In human fluids, the presence of OCs' residues is indicative of past and present exposure (Jaga and Dharmani, 2003). Human body burden of OCs is still a matter of public health concern because of their action as endocrine disrupters and as suspected carcinogens (Colborn et al., 1993, Soto et al., 1995, Wolff et al., 2000, Snedeker, 2001, López-Cervantes et al., 2004).

Although in most countries, among them Spain, most OCs were banned in the 1970s (Ferrer et al., 1992, Gómez-Catalán et al., 1993, Porta et al., 2002, Botella et al., 2004), persistent OCs' residues could be measured in serum and other biological samples as a result of their bioaccumulation (DeVoto et al., 1998, Snedeker, 2001, Cruz et al., 2003, Botella et al., 2004). Nowadays, it is well established that the problem of organochlorine pesticides' residues goes beyond occupational exposure and affects a general population (Bates et al., 2005), as is demonstrated by the fact that factors, such as age, gender, and type of habitat, have to be taken into account (Glynn et al., 2003, Zumbado et al., 2005). Nowadays, human exposure comes basically from environmental or dietary sources (Ecobichon, 1995, Fries, 1995, Bolt and Degen, 2002).

In Spanish population groups, the presence of OCs' residue (pesticides, PCBs and PCDD/PCDFs) has been measured previously (Camps et al., 1989, Ferrer et al., 1992, Gómez-Catalán et al., 1993, Falcón et al., 2004, Botella et al., 2004). 80–100% of the Spanish population has been reported to present detectable levels of OCs' residues (Porta et al., 2002). Nevertheless, most studies were developed on biological samples other than serum, and they did not analyze a representative sample of the general population. It must be highlighted that the unique study that analyze the presence of OCs' residues in a representative sample of a general population from Spain was developed by our group (Zumbado et al., 2005).

The population of the Canary Islands (Spain) is an interesting group of study due to the relatively isolated condition of the Archipelago, especially in the smaller islands. Geographical variations in OCs' serum levels may indicate differences on the local use of pesticides, mainly in agricultural practices, and subsequent environmental pollution. As demonstrated previously by our group, the Canary Islands population presents a high degree of contamination by OCs–DDT derivatives that could be related with a current source of DDT (Zumbado et al., 2005).

In 1998, around 700 serum samples from a representative sample of the total population of the Canary Islands were obtained in the context of a nutritional survey (Canary Islands Nutrition Survey, ENCA) (Serra-Majem et al., 2000a, Serra-Majem et al., 2000b, Díaz Romero et al., 2001).

As a continuation of previously published study (Zumbado et al., 2005), we analyzed the serum samples from ENCA study in order to evaluate human contamination by other OCs in Canarian people. The purpose of the present study has been to determine the body burden of 4 selected OC pesticides (lindane, aldrin, endrin and dieldrin) in serum samples from the ENCA study and to explore associations between OC levels and sociodemographic and geographical factors.

Section snippets

Study area

The Canary Islands are located 1600 km away from southwest Spain, in the Atlantic Ocean, and hardly 100 km from the nearest point of the North African coast (southwest of Morocco) (see Fig. 1). Geographically, the Islands are part of the African continent, yet from a historical, economic, political and socio-cultural point of view the Canaries are completely European. The Archipelago consists of seven major islands. The population of the Canary Islands between 6 and 75 years old was, at the moment

Occurrence of selected OCs' residues in serum samples

As presented in Table 2, more than 90% of serum samples showed presence of OCs' residues. Cyclodienes were the most frequently detected although in different degree among them. Three out of every four subjects present endrin detectable levels, while only one fourth of subjects present dieldrin detectable levels. Lindane was present in nearly 60% of the samples.

Table 2 shows serum OCs' concentration. Endrin was the residue of OCs that we found in highest concentrations (mean values of 136.7 ng/g

Discussion

The present study reports for the first time the presence of cyclodiene and lindane residues in a representative sample of people living in a Spanish region (the Canary Islands Atlantic Archipelago). This analysis of the Canarian population is consistent with numerous studies in other populations that have shown the difficulty of analyzing human data due to the diversity of parameters to take into account.

The problem of OCs' pollutants is far from being totally understood (Ahlborg et al., 1995,

Acknowledgements

The authors acknowledge the working group of the Nutritional Survey of the Canary Islands (Canary Health Service) for their collaboration in the collection of information as well as in the sampling and storage of the serum samples. Also, the authors gratefully acknowledge the help of Dr. Isaías Naranjo Acosta, from the University of La Laguna, who checked the English version of this article.

This work has been supported by the Canarian Health Service through a research agreement with the

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