by Dr. Hernán Málaga

Plants, livestock, and domestic fowl, as well as the rest of the animals destined to serve as food, may or may not exposed purposely to great variety of chemical products, such as drugs, hormones, pesticides, and other environmental pollutants. The drugs and hormones are provided to the animals to promote their growth or to treat or prevent disease. Pesticides are applied to eliminate the parasites of both plants and animals. This exposure, intentional or not, can give rise to residues in food. The medical literature describes very few documented cases in which the chemical residues present in food have been identified as harmful to the health of the consumers since in the majority of the cases the reactions are slight, for example, the sensitivity reactions induced by penicillins. However, public concern over the presence of residues in food is very important since the greatest injuries from pesticides do not inevitably occur as acute intoxications, nor lead to immediate death; perhaps the lack of studies in humans should not be understood as synonymous with a test of the safety of these products (Arnold, D. 1991).

Drugs, such as hormones and antibiotics, are useful to livestock producers in improving the health and/or growth rate of animals; it is essential that there be no hazardous residues of these chemicals that pass to the consumer. Diethylstilbestrol has been shown to produce cancer in laboratory animals and in man; this hormone was used in a pellet that was implanted in the necks of birds and was given to cattle, either mixed in food or through implants; residues of the hormone were found in meat from the animals treated. With regard to antibiotics, it is possible that some bacteria existing in the animals develop resistance to them; hence in the United States the use of penicillin, chlorotetracycline, and oxytetracycline in animal feed requires special FDA approval (K. Longree, 1980).

With regard to environmental pollutants, in recent years the presence of relatively high quantities of toxic metals, such as copper, lead, zinc, and mercury in marine products and other species, has also been a matter of concern since there are many possibilities for direct or indirect contamination by toxic metals in water and on land. One example is the outbreak of neurological mercury intoxication through fish in Minamata, Japan, in the 1950s, which caused the authorities to be concerned with regulating these residues in food (K. Longree, 1980).

In addition, in exposed working populations, such as laborers, fumigators, or applicators, various effects on the reproductory and central nervous systems have been recorded and the risk of cancer has been established, not only for those directly exposed, but also for their wives and children who may wash their clothes, carry meals to them in the field, or help them in their work (L. Mbert, 1983). Neither can the importance of the use of pesticides on the health of workers in the agricultural sector be ruled out, since it has been suggested that long-term exposure to pesticides could result in cancer of lymphatic and hematopoietic tissues in women and cancer of the rectum (Y. Zhong and V. Raflisson, 1996). Association has also been shown in a study of cases and controls of soft-tissue sarcoma, Hodgkin’s disease, and non-Hodgkin's lymphoma (NHL) in which a ratio of inequalities of 1.6 was found, with limits of (0.9 < 1w < 2.6) with 95% confidence.

With respect to the relationship between the use of agricultural herbicides and NHL, the relative risk of NHL increased with the number of days of exposure to the herbicide per year and exposed men had a risk of NHL six times greater than nonfarmers and those who mixed or applied herbicides had a risk eight times greater. The excesses are associated with herbicides based on phenoxyacetic acid (S. Hoar et al., 1986). The use of dibromochloropropane in the 1970s caused the sterilization of 1,500 banana workers in Costa Rica (L.A. Thrupp, 1991). In addition to the importance of the multiple problems of intoxication by exposure and/or poor handling of insecticides, it should be of concern, for example, that 6,000 liters of insecticides are used weekly per hectare in floriculture in Bogotá (CBS, 1997).

The rural population of our countries always grew in parallel to the total population. However, in countries like France there was a break in 1850; with the emergence of rural desertification the population migrated and began to expand the cities. This history has been repeated in practically all the countries of the world, in Europe during the 17th century, in Flanders and the Netherlands, and then in the United Kingdom and France in the 19th century. All this was related to the abandonment of the use of natural fertilizers and the practice of allowing the land to lie fallow and to the intensification of livestock raising (P. Burger, 1992).

In America the greatest threat emerging in the large ecosystems comes from deforestation in the expansion of the areas used for agriculture or wood production; from erosion and loss of soil fertility due to poor cropping techniques; from contamination of water sources by agricultural chemicals, which were paradoxically one of the most significant factors in the increase of the agricultural and livestock productivity; from the desertification that has been produced around the most arid places, through overpasturing and some forms of cultivation that are detrimental to the land; and from the salinization of the soils within irrigation systems (IBD, UNDP, 1992).

In all our countries we have been witnesses to the development of wide-spread, serious problems that were born of the activities of conventional agriculture, which means that it has become necessary to establish legal restrictions on agricultural practices. However, they unfortunately tend to come too late to stop irreversible damages to the environment and they also bring with them deep injustices, imbalances, and new problems, without really solving the original ones (IFOAM, 1992).

For this situation the rescue of the ancestral social, political, and economic systems of production becomes a priority, since these were highly developed; they permitted the exploitation of the existing resources, keeping the ecological balance of their areas and making it possible for the people to remain there for an indefinite time (J.O. Quintana, 1992). This was done by community decision on both what the agricultural sector should produce and how, as well as on the global scheme of its development, since the collective need prevailed over the individual. Currently, this is made feasible at the local level through the empowerment of the neglected, the principle that is expressed in the WHO healthy cities movement and, in the country, in the healthy municipalities initiative by La Paz (OPS, Ministerio de Salud, 1997).

Ecological agriculture would represent a mimicry of natural ecosystems. There are natural ecosystems that are productive. At the etymological level ecological agriculture would mean mimicking those ecosystems and increasing their value, that is, transforming them into productive agricultural systems (C. Beau, 1992).

Thus the essential purposes of ecological agriculture are:

• To produce highly nutritious food in sufficient quantity.

• To interact constructively and energetically with all the natural systems and cycles.

• To promote and intensify the biotic cycles within the agrarian system, including microorganisms--the flora and fauna in the soil--and plants and animals.

• To maintain and increase the fertility of the soils over the long term.

• To use to the utmost the renewable resources in locally organized agricultural systems.

• To work as much as possible within a closed system with regard to the organic matter and the mineral nutrients.

• To provide livestock with the living conditions that allow them to carry out the basic aspects of their innate behavior.

• To avoid all forms of contamination that can result from agricultural techniques.

• To maintain the genetic diversity of the agrarian system and its environment, including protecting the habitats of plants and wild animals.

• To concede that the farmers should obtain a satisfactory income and carry out gratifying work in a healthy space.

• To consider the broader social and ecological impact of the agrarian system.

1. In order to achieve these objectives, the ecological agricultural movement has adopted certain techniques that respect the natural ecological balances and allow avoidance of those products (such as synthetic fertilizers and pesticides) and those methods (such as forced plant and animal growth and industrialization of livestock) that nullify efforts to achieve the cited ends.
2. When compromise is unavoidable due to the ecological or economic conditions in which we live, the limits should be defined clearly (IFOAM, 1992).

These rules can be broken easily, which means that their control requires great transparency from the farmers, the industrialists, and the merchants as well as broad decentralized state participation to protect the community from fraud and possible cumulative exposure to toxicity through its food. For these reasons the governments began to strengthen the institutions connected with the problem and are investigating the most important products in the national diets in order to estimate the exposure of the populations, carrying out specific studies of pesticide residues and detecting critical situations, such as those of vegetables with edible leaves in Belgium (W. Dejonckheere et al., 1990). Plans are being executed to reduce the use of pesticides in native and imported foods. A comparison of sequential time periods showed a reduction between the baseline period from 1981 to 1985 and the period from1990 to 1994 in insecticide residues in food and between the baseline period and the period from 1991 to 1995 in intoxications and quantities sold in Sweden (G. Ekström et al., 1996). Residues of DDT are still being found in breast milk of women in rural areas, where DDT continues to be used in agricultural activities and in malaria control (R. Brunetto et al., 1996).

For the purpose of advising governments with regard to acute toxicity, hypersensitivity, mutagenicity, carcinogenicity, reproduction, teratogenicity, vital functions, permanent debilitating effects, absorption, and principal metabolites, (D. Arnold, 1991) there are world-level expert committees that meet periodically, such as the Joint FAO/WHO Committee of Experts on Food Additives. Its importance was evaluated in the recent GATT Agreement on the Application of Sanitary and Phytosanitary Measures, which contains Codex standards, Codes of Practices, and maximum residue levels for reference purposes in case of disputes between countries that maintain trade relations (F. Zenny, 1995). By 1994 this Committee had already met six times about residues of veterinary drugs in food, in response to a recommendation of the Joint FAO/WHO Commission of 1984 to hold annual meetings on all issues related to pesticide residues. Its fundamental objective is to establish the maximum residual limits (MRL) of the Codex, to facilitate international trade while at the same time protecting the health of the consumer. For the sake of the public's health, the MRL are established at levels no higher than those which result from the use of pesticides in accordance with correct agricultural practices.

The possibility has been raised that the MRL in the Codex could give rise to a situation in which the admissible daily intake of a pesticide is exceeded. Only the execution of studies on food intake would allow a definitive response to this question. When it is not possible to carry out such studies or when the pesticide has not been utilized for a period of time, it is necessary to predict the intake of residues of the pesticide on the basis of the data available.

In the guidelines prepared to help the national authorities to evaluate the degree of acceptability of the MRL, procedures are described to predict the intake of pesticide residues on food (WHO, 1995). Since 1976 WHO has been the Executive Agency for the Global Environment Monitoring System--Food Contamination Monitoring and Program Evaluation (GEMS-FOOD), which jointly with the WHO Collaborating Center for the Analysis of Pesticides and Training in Darmstadt, Germany, proposed in 1996 an analytical quality assessment. To that end samples were sent from participating institutions of the Member States to evaluate their analytical performance, a program in which ICA participates with 72 world laboratories (J. Brodeser, 1977).

There is also the Codex Committee on Pesticide Residues, an intergovernmental agency that advises the Codex Alimentarius Commission. The purpose of the Committee is to offer guidelines to the Member States of FAO and of WHO and to the Codex Alimentarius Commission on matters of public health relating to residues of veterinary drugs in food of animal origin. Its specific tasks are as follows:

1. To formulate principles for evaluation of the safety of veterinary drug residues in food and to establish the admissible levels of daily intake and the corresponding maximum residue levels, in accordance with proper handling practices.

2. To evaluate the safety of the residues of certain veterinary drugs (UNDP, FAO, WHO, 1989).

Finally, we want to promote the use of ecological agriculture, favoring agricultural development without the implication of risks for the human population.

1. ARNOLD, D. (1991) Consecuencias para la Salud Animal y la Salud Pública de la Presencia de Residuos Químicos (Medicamentos, Hormonas y Pesticidas) en los Animales y Productos de Origen Animal. OIE 59° Sesión General, París, 28 pp.

2. LONGREE, K. (1980) Quantity Food Sanitation. Willey-Interscience, 3rd Ed. New York, in Chpt. III Foodborneillness 29-56 pp.

3. LONGREE, K. (1980) Quantity Food Sanitation, Willey-Interscience 3rd Ed. New York, in Chpt. VI Reservoirs of Microorganisms causing Foodborn Gastroenteric Outbreaks: Food Supply, 131-175 pp.

4. ALBERT, L. (1986) Repercusiones del uso de Plaguicidas sobre Ambiente y Salud in Plaguicideas, Salud y Ambiente. Centro Panamericano de Ecologia Humana y Salud, Instituto Nacional de Investigaciones sobre Recursos Bioticos, México: 49-59 pp.

5. ZHONG , Y., RAFNSSON, V. (1996) Cancer Incidence among Icelandic Pesticide Users. Int. I of Epidemiology 25 (6): 1117-1124.

6. HOAR, S., BLAIR, A., HOLMES, F., BOYSEN, C., ROBEL, R, HOOVER, R, FRAUMENI, J., (1986) Uso de Herbicidas Agrícolas y Riesgo de Linfoma y de Sarcoma de Tejidos Blandos JAMA 256 (9): 1141-1147 pp.

7. THRUPP, L.A. (1991) Sterilization of workers from pesticide exposure: The causes and consequences of DBCP - induces damage in Costa Rica and beyond. Int. J. Health serv. 4: 731-57, bibliografia no consultada citada por Wesseling, L et al (1997). Cancer in Banana Plantation Workers in Costa Rica. Int. I. of Epidem. 25 (6)1125-1131.

8. CBS, 1997, Noticiero del Mediodía, Junio.

9. BURGER, P. (1192) Agrobiología y Desarrollo Sostenible. Límites comparativos y Condiciones de una Alternativa Económica in Agricultura Biológica y Desarrollo. Ministerio de Agricultura, Pesca y Alimentación, Madrid 17-30 pp.

10. BID, PNUD (1992). Nuestra Propia Agenda, Comisión de Desarrollo y Medio Ambiente de America Latina y el Caribe, 102 pp.

11. IFOAM (1992) Normas básicas para la Agricultura Ecologica y el Procesamiento de Alimentos. Asamlea General de IFOAM, Sao Paulo, Brasil 28 pp.

12. QUINTANA, J.O. (1992) Relación entre Métodos Agrícolas Tradicionales y Ancestrales y Técnicas Actuales de la Agricultura Biológica in Agricultura Biológica y Desarrollo. Ministerio de Agricultura, Pesca y Alimentación, Madrid, 79-92 pp.

13. OPS, MINISTERlO DE SALUD DE COLOMBIA (1997), Municipios Saludables por la Paz, OPS, Bogotá, 37 pp en Prensa.

14. BEAU, C (1992) Experiencias en Agrobiología hacia nuevos métodos de Investigación y Desarrollo in Agricultura Biológica y Desarrollo, Ministerio de Agricultura, Pesca y Alimentación, Madrid: 49-56 pp.

15. DEJONCKHEERE, W., STEURBAUT, W., DRIEGHE, S., VERSTRAETEN, R., BRAECKMAN, H., (1996) Monitoring of Pesticide Residues in Fresh Vegetables, Fruits and other Selected Food Items in Belgium, 1991-1993. J. AOAC Int; 79 (1):97- 110, pp.

16. EKSTROM, G., HEMMING, H., PALMBORG, M. (1996) Swedish Pesticides Risk Reduction 1981-1995: Food Residues, Health Hazzard and Reported Poisonings. Rev. Environ Contam. Toxicol,; 147:119-147 pp.

17. BRUNETTO, R., LEON, A., BURGUERA, J.L., BURGUERA, M. (1996) Levels of DDT Residues in Human Milk of Venezuelan Women from various Rural Populations. Sci. Total Environ; 186 (3): 203-7 pp.

18. ZENNY, F (1995), Discurso de Inauguración in Evaluación de Residuos de Ciertos Fármacos de Uso Veterinario en los Alimentos. 42° Informe Comité Mixto FAO/OMS de Expertos en Aditivos Alimentarios, OMS, Serie de Informes Técnicos Nr. 851, pp. 1.

19. OMS (1995) Evaluación de Residuos de ciertos Fármacos de Uso Veterinario en los Alimentos. 42° Informe Comité Mixto FAO/OMS de expertos en Aditivos Alimentarios, OMS. Serie de Informes Técnicos Nr. 851, 42 pp.

20. BRODESER, J. (1997) Report on the Analytical Quality Assurance Excercise on Pesticides in Skimmed Milk Powder. GTZ Analytical Quality Assurance (AQA) Study on Pesticide Residues 1996. Eschborn, Alemania, 7 pp.

21. PNUD, FAO, OMS (1990), Orientaciones para predecir la Ingesta Alimenataria de Residuos de Plaguicida. OMS, Ginebra, 28 pp.