Total arsenic, lead, and cadmium levels in vegetables cultivated at the Andean villages of northern Chile

Abstract

Various vegetables (broad beans, corn, potato, alfalfa and onion) were sampled in northern Chile, Antofagasta Region. They are the basis of human nutrition in this region and of great relevance to human health. This region is characterized by volcanic events (eruptions, thermal springs, etc.). Most of the vegetables cultivated in this area enter the local markets for a population of approximately 4000 people, whose ancestors were mainly atacameños and quechuas (local indigenous people). The cadmium and lead in these foods was determined by differential pulse anodic stripping voltammetry (DPASV). Results indicate that the highest concentration of Pb and Cd are in the potato skin, while the edible part of the potatoes contained a lower concentration of these metals. The INAA analyses of As in the vegetables from Socaire and Talabre, two towns located close to active volcanoes (e.g. Lascar), show a very high As content: 1850 μg/kg in corn (Socaire) and 860 μg/kg in potatoes (+skin) (Talabre). These values exceed the National Standard for arsenic (500 μg/kg) by approximately 400% and 180%, respectively. In general, the data show a concentration of Pb greater than Cd with the potential for some vegetables to accumulate heavy metals. The values, expressed in fresh weight, vary from 0.2 to 40 μg/g for Cd and from 0.6 to 94 μg/g for Pb. These concentration intervals, except that of arsenic, are within the recommended standards in the Food Sanitary Regulation (Decree 977), which, expressed as fresh weight, must be equal to or smaller than 500 μg/kg for Pb. There is no legal standard for Cd.

Introduction

Heavy metals such as Cd and Pb, and the metaloid arsenic (As), have long been known as a major contamination problem, not only for working conditions but also for the environment (Freiberg et al., 1979, Merian, 1984). In general, these metals are not biodegradable and therefore they can accumulate in human vital organs, producing progressive toxic effects (Stoeppler, 1984, Bertram et al., 1985). Arsenic, Cd and Pb are environmental pollutants mainly of anthropogenic origin (Nriagu, 1989, Nriagu, 1994). However, as with As, their natural origin may have an important contribution from volcanism (Campano et al., 1976, Campano and Guerra, 1979). Borgoño et al. (1977) report high arsenic concentrations in northern Chilean water; Smith et al. (1998) reported an increase of cancer mortality in this region. The zone studied is located in the pre-Andean area in northern Chile, the IInd Region. This is an active volcanic zone within which approximately 4000 people live (CODEFF, 1990). It is characterized as one of the world’s most arid zones. Thus, its ecological systems are extremely fragile. Very high As contents (in some cases higher than 2000 μg/l) in the surface water of the rivers in the pre-Andes have been recently reported (ESSAN, S.A., 1996, Queirolo et al., 1999).

Several scattered villages, devoted to agricultural activities, cultivate 2193 ha. Irrigation is precarious; it is socially organized and depends basically on the availability of enough water and water rights, which were determined by the communities. The main crops are potatoes, broad beans, onions, garlic, alfalfa and maize; they eat mainly camel meat. Agriculture (CONCECOL, 1988) accounts for approximately 25–76% of the income and 81–99% of its production is for self-consumption.

This research is intended to quantify these potentially ecotoxic pollutant elements in the matrixes studied; to help creating a database for estimating the Cd, Pb, and As content in the native farmers’ diet; and to provide data — which is scarce in relation to that of Europe, North America and Asia — on heavy metal indicators for South America (Brooks, 1993).