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By Nicolás Olea
The consequences of pesticide exposure on the development and functionality of different organs and systems is not well known, but ranges from neurological, reproductive, endocrine or immunological disorders, to functional failures and significant behavioral disorders.
It is a frequently reported fact that world agricultural production is growing in general terms, and that this trend is expected to continue in the coming years (Dyson, 1999). It is also true that the increase in agri-food production is a universal phenomenon and that it is the countries with the greatest deficits that have seen their crops grow in the most striking way. It has been mentioned that between 1961 and 1994 this growth was firm and continuous for most countries and reached the highest levels in some African countries that saw agricultural production double. However, during those same years the population growth rates in many of the underdeveloped and developing countries have been higher than in previous periods, so it is presumably that the increase in local agricultural production, although important, cannot meet the demand. In addition, experts have detected that the rate of productive growth is suffering a continuous slowdown, in such a way that the most pessimists predict a strong imbalance between food production and the increase in demand, which would lead, in a not too long time , to the increase of the populations very insufficiently supplied (food and agriculture, World Resources, 1997).
A detailed analysis of the current situation and prospects for years to come indicates that, in part, the solution to the serious problem of food production and supply to the most deficient populations is through better distribution of the product. From this point of view, increased production, although necessary, is not everything and attention should also be paid to facilitating access to food for the most needy. In fact, when the overproduction of surpluses imposed by market rules is compared with the failure of production induction in underdeveloped geographic areas, regional inequalities are alarming.
In the increase in agricultural production, several reasons are adduced by experts, including the use of new varieties of seeds and the rational use of water, to which are the use of new varieties of seeds and the rational use of water, to which are added the use of fertilizers and the increasingly frequent use of pesticides. In this sense, it is interesting to note that agricultural research in recent years has been directed to the study of increased production and cost reduction in food processing and has forgotten, until very recently, the aspects related to environmental and commercial impact , social, economic or cultural of the different techniques and agrarian models proposed (Groome, 1998). In general, it is accepted that the increase in global production could come from the hand of one or more of these strategies:
· The increase in the area dedicated to agriculture.
· Increased crop yields.
· Improvement in agronomic practices.
· Greater efficiency in the use of water.
. Loss reduction after harvest.
It has also been mentioned, perhaps not too often, that some of these interventions may be self-limiting in themselves and that although they allow a substantial increase in production, and thus offset the growing demand, their indirect cost may not be acceptable (Muñoz E, 1998). ). From an environmental and human point of view, it has been perceived that some of the proposed actions have negative consequences on the environment and, directly or indirectly, on human health. Perhaps the paradigmatic example is the case of the abusive use of synthetic chemicals, such as fertilizers and pesticides, which have frequently contaminated soils, aquifers, animals and even human beings. It is true that the health cost is not well known due, on the one hand, to the non-specificity of the pathological effect and the latency time elapsed between exposure and the manifestation of symptoms, on the other, to the universality of the exposure that does not allow Identify nowadays free populations of pesticide residue.
Human exposure to pesticides has been a well-documented fact during the last thirty years, although its real consequences are beginning to be seen now that more than one generation has suffered such environmental harassment. Faced with the relatively rich information on the acute effects of pesticides obtained from the detailed study of cases of poisoning generally in professionally exposed workers, the paucity of data on the long-term effects of such exposure is striking. The consequences of pesticide exposure on the development and functionality of different organs and systems is not well known, but ranges from neurological, reproductive, endocrine or immunological alterations, to functional failures and significant behavioral alterations (Olea et al., 1996 ; Parrón et al. 1996).
The studies on cancer incidence and mortality in agricultural populations are well known and have been repeating a few well-documented facts for decades (For a review see Maroni and Fait, 1993). the risk of death from cancer in the agricultural population is higher than the general population for some tumor sites such as brain tumors, lung, ovarian and prostate cancer, soft tissue sarcomas and some specific types of leukemia. Despite this trend, the greatest difficulty has been found in establishing a causal relationship between exposure to a given chemical compound and the risk of suffering from cancer. These drawbacks are even greater when epidemiologists face the lack of information in the classification of the exposed population, which, for example, makes it impossible to identify the labor activity of working women through death records (López Abente, 1991) .
It is true that some progress has been made in recent years due to the focus on studying the effect on the general population of widely used pesticides such as DDT. Chronic exposure to DDT and the accumulation of its metabolites in fatty tissue have tried to relate, without much success, to the increase in cases of breast cancer. Unfortunately, these works have been limited to typifying human exposure to one, or a few, chemical compounds to which all the suspicion in the chemical compound-cancer association has been naively attributed and they have "forgotten" the infinity of chemical compounds with Similar characteristics to which these individuals have been exposed and for which there seems to be no form of evaluation (Fernández et al. 1998). The theoretically rational concepts of synergism, additivity or antagonism are rarely considered in the actual design of environmental studies, due in part to the difficulty of their implementation.
Pesticides, Pesticides, Phytosanitary, Agrochemicals
Synthetic pesticides are a very diverse group of chemicals that include insecticides, fungicides, herbicides, acaricides, molluscicides, and rodenticides. Today there are approximately six hundred active ingredients that are combined with each other and with the so-called inert ingredients to give a wide range of commercial mixtures with very different uses and domestic and agricultural applications.
The term pesticide has very diverse connotations that are worth briefly considering. On the one hand, it must be remembered that alongside the active ingredients are the isomers and metabolites of these compounds that may be responsible for unsuspected biological effects for the nominal compound recognized as the main one.
Second, the semantic consideration of the term itself, which has evolved from its initial name of pesticide (annihilator of "pests"), the best translation of which is the term pesticide, which has led us, insensibly, to the semantic transformation into " phytosanitary "," agricultural chemical compounds "or" agrochemicals "and which goes up to the most current of" crop protection chemical ". Terms promoted by the chemical manufacturing industry that sees in the change of terminology a more environmentally friendly approach. It is not surprising, therefore, that these companies that have produced insecticides for years are changing their image as biocides and are now presenting themselves under the banner of "life sciences".
If it is also considered that other compounds such as wood preservatives, plant growth regulators, defoliants and desiccants, are also included within a generic group of phytosanitary products, it is easy to understand that the term pesticides, phytosanitary or chemical compound agricultural is wide enough to not allow the generalizations we are used to.
The era of chemical pesticides began in the last century when sulfides were developed and found practical application as fungicides. Subsequently, arsenical compounds were used to treat insect pests in agricultural production. In both cases they were highly toxic substances, which limited their widespread use. It was in 1940 when the first organochlorine pesticides appeared which have their maximum exponent in dichloro diphenyl trichloroethane or DDT. They were used both in agricultural treatments and in the control of pests carried by carrier insects. Since, in principle, these organochlorines present low toxicity, their use was greatly favored and they occupied a dominant position among the newly synthesized chemical pesticides.
In 1962 after the publication of Rachel Carson's book, The Silent Spring, the idea of the persistence in the food chain of organochlorine pesticides spread which, together with the knowledge of reproductive toxicity in some animal species, attracted public attention to these compounds until that moment considered innocuous. It was soon learned that some animal species that had accumulated a large amount of DDT and its derivatives had serious reproductive failures, which led to the prohibition of the use of some organochlorines, a fact that occurred in 1972 in the case of DDT in the United States and which led to one of the first interventions of the recently created Environmental Protection Agency.
The "authorized" life of DDT was thirty years, counting from its commercialization to the end of its legal use, an excessively long time for a compound that has been shown to be bioaccumulative and toxic. During this time the accumulation of the pesticide in soils, aquifers and in the food chain is tremendously significant, in such a way that today there is a human population, for example, that does not contain significantly important levels of DDT and its accumulated derivatives, due to its solubility in fat and deposit in adipose tissue. In addition, although its use is restricted or prohibited, the truth is that its production and sale in developing countries is free, since it is used on a regular basis for the treatment of pests, vehicles of infective organisms.
Despite their strict regulation, there is still a trade for organochlorines either because their use is restricted to specific applications or because strangely they have not been classified under this generic name. Such is the case of endosulfan, a diene derivative with six chlorine atoms in its molecular structure, whose use in southern European countries places it at the highest levels.
Organochlorines relegated to second place, the main pesticides used today in developed countries belong to the group of organophosphates, carbamates and pyrethroids. These are chemical compounds with a much shorter half-life than organochlorines, so that they do not accumulate in adipose tissue. These are joined by new compounds that are developed by the synthetic chemical industry, which, as one of its spokesmen recently declared, is committed to sustainable development in agricultural production. In fact, the extension of this commitment has brought with it a controversy between industry, regulators, environmentalists and scientists that seems to have only just begun (Durán et al., 1998).
Leading agricultural companies have reported spending more than $ 3 billion on research and development annually (Samo 1997). New pesticides with less environmental impact and the development of genetically modified plants are the target of much of this activity. However, practices as simple as the recognition and isolation of the active isomer within a commercial mixture have led to a 50% reduction in the total amount of fungicide used without loss of treatment efficacy. Other examples are frequently aired by the marketers of large companies who are torn between changing their public image and maintaining profits despite the large investment in new compounds.
Paradigm of this environmental crisis is the controversy established, first in Europe and later transferred to the United States, when the industry faces the indications of the regulatory bodies that have found in the Precautionary Principle a conceptual basis to act preventively in the face of technical innovations not well evaluated from the point of view of human health and environmental impact.
Intensive Agriculture in the Southeast of Spain.
The technical revolution, mechanization and the use of chemicals, both fertilizers and pesticides, allowed agriculture to enter an economic world dominated by strong market rules. Intensive agriculture developed in a particularly important way in some geographical areas is a good example of this situation. The production systems, the consumption of energy, water and phytosanitary products and the yield in production seem to correspond to industrial rather than agricultural activities, so on more than one occasion the term industrial agriculture has been used to designate this type of activity ( Massaro et al., 1998).
Industrial development over a century old is an inexhaustible source of examples of unpredictability and mistakes in terms of environmental protection and human health (García, 1999). Therefore, it can be a good model of experiences so as not to fall into the same past mistakes. Despite this conviction, the promoters of intensive agriculture seem to be more concerned with strict compliance with the established norms than with the real safety of the people directly and indirectly exposed.
Due to its physical characteristics, the Mediterranean coast has become a good seat for intensive agricultural practices. The flourishing of crops under plastic in the provinces of Almería and Granada is a good example of this. This type of crops requires special treatments for both tillage and the use of fertilizers and pesticides that places them among the agricultural activities with the highest consumption of phytosanitary products.
The surface of the Andalusian region is 87,268 km2 which corresponds to 17.3% of the surface of Spain. It is an eminently agricultural region characterized by its diversity in which fruits and vegetables represent 35% of agricultural production despite the fact that the area dedicated to these crops is only 7.7% of the cultivated area.
More than 40% of vegetable production takes place in the eastern Andalusian provinces near the Mediterranean, where cultivation under plastic was developed since the 1950s, a model of intensive production with very high levels of yield. and extra-early harvests. About 2,800,000 tons of vegetables were produced in Almería in 1997, with 45% of the product dedicated to export (Herrera et al., 1998). The special physical conditions of the environment, which has a high average number of hours of sunshine per year, the almost total absence of frosts and the existence of aquifers together with the creation of an artificial soil, allowed the development of this type of crops. The success of the production system has led to changes in the structure of the territory and the landscape. It is, in short, an urban type organization embedded in an agricultural environment in which greenhouses and human settlements intertwine and which determines a high anthropization of the environment.
Humidity, air quality, temperature and water supply are carefully controlled inside the greenhouse. The use of pesticides is common and achieves the highest employment rates of all forms of agriculture. An average of 40 kg per hectare of a mixture of various pesticides is common in greenhouse cultivation, which increases even more if soil disinfection is considered.
The study carried out by Massaro and collaborators in the greenhouse area in the western area of Almeria revealed the following facts: 1. The existence of new reparcelling with specific demands for supplies, access roads and movement of private waste. 2. A high degree of occupation and modification of the soil with costs, inputs and productive level typical of an industrial region. 3. The great demographic expansion that has brought about the population concentration in urban centers with the consequent administrative changes (Table 1). 4. The emergence of new diseases caused by acute poisonings and chronic exposure to pesticides and chemicals used in agriculture.
Slowly but steadily, we are witnessing the appearance of medical publications that objectively collect the impression of health workers regarding health disorders in the population of the southeast of the peninsula exposed to pesticides.
Acute poisonings, as noted above, are well documented. The excellent work of Martín Rubí et al. (1996) collected the cases of acute poisoning that were treated at the Torrecárdenas hospital in Almería and that required hospitalization in the Intensive Care Unit. This is the presentation of 506 cases of intoxication in which the most frequent culprit was an organophosphate pesticide (Methamidophos, chlorpyrifos and parathion), which triggered a picture of cholinergic symptoms - bronchorrhea, tremors and fasciculations, respiratory depression and loss of consciousness. only 5% of deaths occurred. This work is a good representation of what happens in areas of intensive agriculture: the worker perceives the risk of poisoning by pesticides and relates it to the occupational exposure, but has great difficulty in assigning a long-term harmful effect.
The truth is that the late effects of exposure to pesticides are more subtle in terms of presentation and, therefore, it is more difficult to establish a causal relationship between a single chemical agent, or a specific agricultural practice, and the appearance of an effect. harmful or disease. In this respect, the actual demonstration of exposure is without a doubt the first step that any study must face. The confirmation of the use of a pesticide, its environmental concentration (air, soil, water or food) and the content in the human body are three steps of equal merit when investigating exposure.
Organochlorines with hormonal activity.
Little by little the chronic toxicity of pesticides on animal life and human health is becoming known. The history of human exposure to bioaccumulative pesticides is a recurring story full of mixed messages with more reassuring than realistic intent. If there is a common denominator in studies aimed at demonstrating human exposure to organochlorine pesticides, it is that "historical" pesticides:
They are present in our environment and represent the residue most frequently found in human tissues.
· There does not seem to be a reference population in which the exposure does not exist since impregnation is universal.
· Using the internal dose (amount accumulated in fat of one or a few of these organochlorines) in epidemiological studies and trying to associate it in a particular way with some disease is a worthy task but not without difficulties.
The medical bibliography of the last decade has taught us that the methodological approach indicated in this last point should not be maintained in successive studies. During this time, multiple epidemiological studies have tried, with greater or lesser success, to establish an association between exposure to organochlorine pesticides and the risk of developing breast cancer. Based on previous observations in which a concentration of DDT and its metabolites had been described in the breast tissue of patients affected by breast cancer greater than that found in patients not affected by the malignant tumor process (for a review see Helzlsouer et al., 1999), several studies of large series of patients were successively developed in New York (1993), San Francisco (1994), Vietnam (1997), several European countries, including Spain (1997), Mexico (1997), Denmark ( 1998) and Washington (1999). The common hypothesis of these studies is that human exposure to DDT / DDE increases the risk of developing breast cancer.
Regardless of this common point, each of these studies also presented particular peculiarities:
· The organic behavior in which to measure DDT and its metabolites could be blood or adipose tissue.
· The prospective or retrospective nature of the designs, that is, the exposure measurement is carried out prior to the diagnosis of the disease or after this event.
· The association of DDT measurement with the quantification of other organochlorine compounds of interest such as polychlorinated biphenyls or PCBs or some other organochlorine pesticides such as mirex, chlordecone, dieldrin, etc.
The results of these works are very different. Some of the studies have assigned a role to DDT in the risk of breast cancer (Wolff, 1995), while most of the studies have failed to establish such an association. In other cases, the risk of tumor disease has been associated with the presence of pesticides other than DDT, such as dieldrin (Hoyer et al., 1998) or mirex (Moysich, 1998).
Two facts underlie the support and interest of this scientific hypothesis. On the one hand, the recognition of the mutagenic / carcinogenic capacity of some pesticides. That is, in the experimental knowledge of its ability to produce tumors in experimental animals. It is well known, and often remembered, that pesticides are designed to kill living things, so the toxicity of these compounds has been frequently evaluated. In fact, in the 1997 report of the Lyon International Agency for Research on Cancer (IARC, 1997), 26 pesticides were classified in the group of substances with sufficient evidence to be considered carcinogens and 19 additional ones in which the tests they were not conclusive but the suspicion was reasonable to enter this toxicological classification.
Second, the relatively old knowledge of the hormonal activity of DDT, its metabolites, and some other organochlorine pesticides. This is a well-known and sufficiently proven phenomenon that it has not been evaluated to its true extent despite the interest of regulatory bodies in addressing the hormonal hypothesis (Endocrine Disrupting Chemicals: A Challenge for the EU ?. 1998).
Currently, the census of organochlorine pesticides with hormonal activity increases almost monthly. After the detailed description of the estrogenicity of DDT and some of its metabolites, it was learned that chlordecone, kepona, dieldrin, toxaphene and endosulfan also appeared as hormonal mimics in different models and specific systems of estrogenic activity.
The ability of environmental pollutants, in general, to interfere with endocrine function was established more than 30 years ago when the drop in the population of piscivorous birds in the United States was associated due to serious reproductive problems caused by p, p- DDE, a metabolite of the organochlorine pesticide DDT (Hickey and Anderson, 1968; Heath et al., 1969). The immediate problem was partially solved with the withdrawal of the pesticide in 1972, although subsequent observations, both in the laboratory and in the field, indicate that DDT and other organochlorine pesticides continue to permeate exposed populations due to their environmental persistence, bioaccumulation in tissues and transmission within the food chain.
Other environmental observations related to the massive exposure of animal populations have helped to understand the problem of hormonal disruption. They are multiple examples collected in the scientific literature. As an example, what happened to the population of alligators in Lake Apopka in Florida, which were accidentally exposed to the pesticide dicofol / keltano, after an accidental spill in 1980. Ten years later the alligator population had dropped significantly, egg mortality had increased, and half of the hatchlings languished and died within ten days. Adolescent females were found to have severe ovarian abnormalities and blood estrogen levels twice as high as normal. Young male alligators were strongly feminized, had abnormally small penises, and had higher levels of estrogen in their blood than normal. The investigations carried out served to conclude that the chemicals that were dumped into the lake had altered the endocrine system of the embryos, limiting the ability of the alligators to reproduce and led to the malformations described (Woodward et al., 1993; Guillette et al., 1995).
More recently, in 1993, the experimental observation relating to disorders of expression of the sexual phenotype in fish was published for the first time. Male fish caught in the vicinity of sewage treatment plants in some English rivers exhibited female sexual characteristics. Furthermore, the production of the vitellogenin protein in the liver of male fish was observed, a highly abnormal fact since it is a protein synthesized in the liver of females in response to an estrogenic signal. Several chemicals, especially the alkylphenols found in detergents and plastics, were then identified as responsible for causing these feminizing effects (Jobling et al., 1993).
Numerous studies have associated the reproductive and endocrine pathologies observed in different animal species with exposure to compounds with hormonal activity that contaminate the environment (Colborn and Clement, 1992; Davis et al., 1993; Colborn et al., 1993). Among the effects evidenced are alterations of thyroid function in birds and fish, decreased fertility in birds, fish, mollusks and mammals, decreased efficiency in the incubation process in fish, birds and turtles, demasculization and feminization of male fish , birds and mammals, defeminization and masculization of female fish, gastropods and birds and finally alterations of the immune system in birds and mammals.
Perhaps one of the best typified alterations in Spain corresponds to the pronounced masculization that gastropods and mollusks present in maritime waters of Galicia (Ruiz et al., 1998), Catalonia (Morcillo et al., 1998) or Huelva (Gómez Ariza et al. ., 1998) and that is unequivocally associated with exposure to tributyltin and other tin derivatives used as anti-algae, which has well-documented hormonal activity in in vitro / in vivo models.
The term endocrine disruptor is currently used to define any chemical compound, an environmental pollutant, which, once incorporated into a living organism, affects the hormonal balance. Although any hormonal system can be involved in this alteration, the information available on the hormonal disruption caused by the agonists / antagonists of the female sex hormones estrogens is qualitatively and quantitatively much superior (Olea et al., 1996; Pazos et al. , 1998; Olea et al., 1998).
Aunque las pautas de presentación de los efectos causados por los disruptores endocrinos varían de una especie a otra y son específicas de cada sustancia química, pueden formularse cuatro enunciados generales (Statement from the work session on health effects of contemporary-use pesticides: the wildlife/human connection, 1.999): 1. Los efectos de los contaminantes pueden ser distintos sobre el embrión, el feto, el organismo perinatal o el adulto. Los efectos se manifiestan con mayor frecuencia en la progenie que en el progenitor expuesto. El momento de la exposición en el organismo en desarrollo es decisivo para determinar el carácter, la gravedad y su evolución. Aunque la exposición crítica tenga lugar durante el desarrollo embrionario, las manifestaciones pueden no ser evidentes hasta la madurez del individuo.
El caso del Endosulfán en España.
El Endosulfán es el pesticida organoclorado que ocupa, hoy día, el primer lugar en consumo en los países industrializados. A diferencia de otros organoclorados "históricos" su uso es frecuente y su empleo en áreas agricultura intensiva en la península Ibérica es una práctica habitual (Olea y cols., 1.996; Olea y cols., 1.999).
En 1.994 Soto y cols. Presentaron el primer informe sobre la estrogenicidad del endosulfán al demostrar que este ejercía un efecto proliferativo sobre células de cáncer de mama mantenidas en cultivo, y que este efecto era comprable al inducido por el estradiol, estrógeno natural. Informes posteriores han confirmado esta observación por lo que endosulfán se clasifica hoy entre los pesticidas estrogénicos con capacidad disruptora endocrina (Soto y cols., 1.995; Vornier y cols., 1.996; Jin y cols., 1.997; Andersen y cols., 1.999). El consumo de cantidades importantes de endosulfán en el medio agrícola ha provocado que su presencia medio ambiental sea cada vez más frecuente. En aquellos trabajos en los que se ha buscado expresamente la persistencia de endosulfán como contaminantes de alimentos, aguas, aire o suelos se ha puesto de manifiesto que hoy día ocupa uno de los primeros lugares en cuanto a concentración y porcentaje de muestras positivas, en muchos casos comparable a la positividad del DDT y sus metabolitos. De hecho los informes científicos sobre la presencia de este pesticida en medio ambiente son un tanto preocupantes. Por ejemplo, endosulfán es el pesticida más frecuentemente encontrado en el análisis de aguas superficiales realizado en Almería (Fernández Alba y cols., 1.998) y en la Comunidad Valenciana (Hernández y cols., 1.996). En el primero de los casos, los estudios de vigilancia llevados a cabo en tierras almerienses durante un año sirvieron para demostrar la presencia y cuantificar la concentración ambiental del endosulfán alfa, beta y sulfato que se mueve en el rango de 0.5-540 ng/l (Penuela y Barceló, 1.998). estos datos parecen confirmar la ubicuidad del pesticida previamente denunciada por Seba y Snedaker (1.995) que refieren a endosulfán como el pesticida más frecuentemente encontrado en la capa superficial de las aguas marítimas.
No sólo en aguas, también en los estudios de calidad del aire se ha determinado la presencia del endosulfán junto a otros organoclorados. Tal es el caso del trabajo recientemente publicado en el que se establece una comparación entre la calidad del aire en dos zonas bien diferenciadas, el Parque Nacional de Ordesa y Monteperdido y un vertedero industrial en Sabiñánigo (Nerin y cols., 1.996). El endosulfán alfa, junto con lindano, hexaclorohexano alfa y hexaclorobenceno, fueron encontrados en todas las muestras tomadas en el Parque Nacional en concentraciones comprendidas entre 70 y 3.076 pg/metro cúbico, hecho que confirma la ubicuidad del residuo de este pesticida. Desde el punto de vista de la exposición humana, tanto con carácter laboral como medio ambiental, es cada vez más frecuente encontrar al pesticida endosulfán en las listas de organoclorados incluidos en las muestras, aunque desgraciadamente en otros trabajos de indudable mérito no fueran seleccionados para estudio (Espigares y cols., 1.997). tanto la intoxicación aguda (García Repetto y cols., 1.998) como la exposición crónica han sido motivo de investigación.
Trabajos recientes han establecido las curvas de disipación del endosulfán alfa, beta y sulfato en el aire de los invernaderos (Vidal y cols., 1.996) y la absorción del pesticida en los films de plástico utilizados para cubrir los suelos agrícolas (Nerín y cols., 1.996). Es interesante hacer notar que este último trabajo demuestra que una vez absorbido el endosulfán permanece en el plástico sin que sufra ningún proceso de degradación, hecho que debe atraer la atención sobre el proceso de reciclamiento de plásticos y la manipulación de este material contaminado.
En lo que respecta a los trabajadores profesionalmente expuestos Delgado y cols., (1.994) estudiaron la exposición dérmica y respiratoria de los trabajadores y Arrebola y cols., (1.999) han publicado recientemente un estudio sobre la excreción urinaria del endosulfán. Tanto endosulfán alfa como beta fueron encontrados en la orina en concentraciones situadas entre 2.239 y 5.368 pg/ml. Loas estudios de exposición a pesticidas en el área de agricultura intensiva almeriense no son nuevos y se mueven entre la medida de la excreción de los compuestos químicos y sus metabolitos y la estimación de los cambios clínicos y bioquímicos objetivados (Parrón y cols., 1.996). La exposición de la población general establecida en áreas eminentemente agrícolas han sido también documentada (Rivas y cols., 1.998; Olea y cols., 1.999). Por ejemplo, en la población infantil de Murcia y granada se encontró el residuo de endosulfán y algunos metabolitos en el 40% y 30% de las muestras de grasa analizadas, respectivamente. Es sorprendente, por otra parte, que al residuo de este pesticida le acompañan otros de compuestos químicos cuyo uso fue prohibido hace décadas. La persistencia medio ambiental de esos organoclorados y la exposición materno-infantil pudiera ser una explicación aceptable para tal exposición.
Trabajos muy recientes han llamado la atención sobre los riesgos para la salud infantil derivados de la exposición intrauterina y durante los primeros meses de la vida, fundamentalmente a través de la lactancia, de niños nacidos de madres profesionalmente expuestas. Las sospechas de una distribución geográfica de una típica alteración del desarrollo genitourinario conocida como criptorquidia o no-descenso testicular denunciada por García Rodríguez y cols., en 1.996, han sido robustecidas por los trabajos de Weidner (1.998) y García (1.999). Si en el primer de los casos se denunciaba el riesgo de padecimiento de la enfermedad en niños nacidos en áreas de gran empleo de pesticidas, cuando se comparaba con municipios con un consumo significativamente menor, el trabajo de Weidner asociaba la actividad laboral materna con el riesgo de dar a luz un hijo sin descenso testicular. El trabajo de García y cols., (1.999), por último, ha servido para asociar la exposición agrícola de las madres durante el mes previo a la concepción y los tres primeros meses de embarazo con el mayor riesgo de malformaciones congénitas en los recién nacidos.
En lo que respecta a los adultos, las fuentes de exposición de la población agrícola general al organoclorado endosulfán pueden ser variadas. Como se ha dicho, existe, de una parte el contacto directo y la inhalación por aquellos individuos total o parcialmente expuestos. De otra, la contaminación de ropas y utensilios utilizados durante los tratamientos agrícolas que son llevados a la residencia del trabajador. Importante también es la exposición alimentaria a través del residuo del pesticida y la contaminación de las aguas de bebida.
Por estas razones ha merecido la atención durante estos últimos años el estudio de la exposición alimentaria al endosulfán. En Aragón se realizó un estudio con objeto de determinar el residuo de 21 organoclorados en la dieta, encontrándose que HCB, lindano, DDT y sus metabolitos y beta endosulfán eran los contaminantes habituales (Lázaro y cols., 1.996). A este respecto es llamativo, por ejemplo, que el informe de Gunderson (1.995) sobre el residuo de pesticidas en la dieta americana demuestre que el endosulfán se encuentra en el 7% de los alimentos investigados que corresponde a una serie de 4.914 muestras y ocupa el primer lugar entre los pesticidas clasificados en el grupo de los disruptores endocrinos seguido de cerca por el residuo de DDT y más lejanamente por el dieldrín toxafeno y el metoxicloro.
Hortalizas cultivadas en invernaderos (Aguilera del Real y cols., 1.997) y naranjas (Torres y cols., 1.996), entre otros cultivos muy diversos, han sido motivo de análisis y estudio para investigar las curvas de eliminación del organoclorado, demostrativas del interés de la comunidad científica por este pesticida. De hecho estos trabajos no hacen si no anticipar la preocupación creciente sobre el residuo de endosulfán en muestras de muy distinto origen, como es el caso de las carnes contaminadas por este pesticida en Australia y las graves consecuencias que ha tenido sobre la exportación.
Muestras de sangre y tejido adiposo humano, tomados de individuos provenientes de áreas donde se ha desarrollado la agricultura intensiva, también han sido motivo de estudio con objeto de investigar la impregnación interna de la población con el residuo de diversos pesticidas y el riesgo de padecimiento de cáncer de mama (Rivas y cols., 1.998). La presencia de op’DDT, pp’DDT, DDE, endosulfán, clordano y metoxicloro fue confirmada en aquellas muestras en que se determinó un exceso de actividad hormonal de carácter estrogénico. Precisamente es esta estimación de la carga hormonal exógena el factor que con mayor fiabilidad identifica el riesgo de padecimiento de la enfermedad tumoral mamaria.
Pero aún así, el caso de endosulfán es un buen ejemplo de la lentitud por parte de la Administración, científicos y productores en dar una respuesta a un problema anunciado. Ha costado años de seguimiento y esfuerzo de diversos grupos de trabajo interesados en una particular forma de toxicidad crónica el acumular la evidencia necesaria para que endosulfán sea considerado un pesticida organoclorado, xenobiótico estrogénico y con una presencia medio ambiental tremendamente importante (Olea y cols., 1.996; Olea y cols., 1.997; Olea y cols., 1.999). Tal evidencia es difícil de conseguir, máxime cuando los ejemplos nos advierten el efecto tardío, dilatado en el tiempo. En casos como éste, más que nunca, el principio de precaución debería ser una premisa de decisión en la mente de todos.
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· Jobling S, Sumpter JA. Detergent components in sewqge effluent are weakly estrogenic to fish: An in vitro study using rainbow trout (Oncorhynchus mykiss) Hepatocytes. Aquatic Toxicol27:361-72,1.993.
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TABLA 1: DISTRIBUCIÓN PARCELARIA EN EL EJIDO.
Tamaño de parcela (m2). Número de parcelas <5.000 4.318 5.000-10.000 4.311 10.001-15.000 1.742 > 15.000 692 Número de parcelas /Propietario Número de propietarios 1 7.233 2-4 1.930 > 4 125
TABLA 2. COMPUESTOS QUÍMICOS DISRUPTORES HORMONALES.
Grupo Disruptores Endocrinos Organohalogenados Dioxinas, furanos, PCBs, PBBs, octacloroestireno, hexaclorobenzeno, pentaclorofenol, bromobisfenol, etc. Pesticidas 2,4,5-T, 2,4-D, alocloro, aldicarb, amitrole, atrazina, benomil, b-HCH, carbaril, clordano, cipermetyrín, DBCP, DDT y metabolitos, dicofol, dieldrín, endoslfán esfenvalerato, etilparatión, fenvalerato, lindano, heptacloro, h-epóxido, keltano, kepona, malation, macozeb, maneb, metomil, metoxicloro, metiran, metribuzin, mirex, nitrofen, oxiclordano, permetrín, piretróides sintéticos, toxafeno, transnonacloro, tributilin, trifluralin, vincozolina, zineb, ziran. Metales pesados Cadmio, mercurio, plomo Ftalatos Di-etilhexilftalato, butilbenzilftalato, di-n-butilftalato, di-n-pentilftalato, di-hexilftalato, di-propilftalato, diciclohexilftalato, dietilftalato. Bisfenoles Bisfenoles, BADGE, bis-DMA Alquilfenoles Penta a dodecilfenol Otros Estirenos, benzopirenos, ácido amsiónico, fenilfenol, butilhidroxianisol, parabenes.
Enviado por Jose Santamarta – Los Verdes-Izquierda Verde
* Por Nicolás Olea
Catedrático de Medicina Interna de la Universidad de Granada
Jefe de la Unidad de Radiología del Hospital Clínico de Granada