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Pesticides In Foods: Some Thoughts

Pesticides are used in both agriculture and in the home. A pesticide is defined by the EPA as any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest. These can be insects, mice, weeds, fungi, bacteria, viruses, and any other "growie" we don't want. The chemicals range from algaecides to plant growth regulators. Each of these have a particular characteristic which is taken into account in use and the presence of residuals. Additionally, Oregon State University maintains a site which allows one to understand the profiles. However, one should hasten tthat all chemicals are not considered to be pesticides.

The advantages and disadvantages of pesticide use has been in the dia for a time. There are many sites on the web which assist in determining these pros and cons. For example, PANNAs a nonprofit citizen-based NGO that advocates adoption of ecologically sound practices in place of pesticide use.

Pesticide use is widespread and monitored by each state and country. The FAO (FAO, 1995) and WHO bring together countries to explore presence and monitoring of pesticide use. There has been established a Global Information Network [GINC] as a world wide information network for safe use of chemicals.

There is general consensus that pesticide use in agriculture has permeated our atmosphere and groundwater.

Pesticides in foods are controlled. The Federal government first began regulating them in 1947. Since that time there have been a number of changes. It is important for the food producer and processor to keep up-to-date on the status of pesticide use. Of particular interest is the Food Quality Protection Act was enacted in 1996. Essentially this act establishes a strong, health-based safety standard for pesticide residues in all foods.

Certainly, with the negatives of pesticides it is critical to remind the reader that there are advantages to there use. The costs and benefits (Bowles and Webster, 1995) can be analyzed. However, even at that, there are processes and procedures for safe and effective use.

The primary detrimental affect of pesticides is their cancer causing potential. As of 1987 (Mott and Snyder, 1987), had identified 55 cancer causing pesticides that leave residues in food. Pesticide Poisoning Handbook indicates symptoms and signs of pesticides. The different categories are listed.

Even though a potential health hazard, if one takes the rather unpopular view that pesticides are ubiquitous at this time and they are always available, the impact of processing, preparation, and handling procedures becomes critical. Can we reduce the pesticide after it leaves the garden? There is evidence that it is possible. For example, Zabick et al. (1996) reported that cooked lake trout had less PCBs, polynuclear aromatic hydrocarbons and organochlorine pesticides than raw trout. Smoked fish had a greater decrease of pesticides and total PCBs than baked, charbroiling, or salt boiling. Overall, she reported an average loss of 30% pesticides during cooking of the Great Lakes trout. Alary et al. (1995) observed the complete degradation of captan during processing (125C, 20 min, pH 4.0) of apple puree. Mott and Snyder (1987) summarizes the possible effect of washing and other simple processes.

The effectiveness of pesticides in controlling pests is documented. Increasingly, there is information regarding how these chemicals impact the pests. This writer certainly recognizes the wealth of literature available on improved crop yield and cosmetics of the use of these chemicals. However, the impact of chemicals on the metabolism of fruits and vegetables has not previously been explored by those of us in food science. This is something that the food scientists have not discussed and reviewed in terms of respective carbohydrate, lipid or protein content, let alone cyanide, arsenic, and other carcinogens.

An initial exploration indicates that some research has been underway for some time by the chemists, weed scientist and horticulturist. Certainly, there is work by Heim et al. (1995) and many others that pesticides such as herbicides can impact a plant by stopping its growth and bringing about death. Heim et al. thought it did this by impacting purine biosynthesis.

The thought that the various pesticides may impact the quality of a fruit or vegetable through its impact upon the various metabolic pathways is not without a research base. Many of the different pesticides may remain in the insoluble cell wall constituents [fiber: cellulose, hemicellulose, pectin]. Schneider et al. (1993) indicates pesticide metabolites are bound and released when cellulase and pectinases solubilize the fiber. Research indicated amitrole application eventually broke down in the cell to carbon dioxide and ethanol. This study raised a number of questions to the reader. Do these products impact sugar, amino acid and protein pathways? Do they "warp" the various metabolic pathways in some manner? Could this result in a softer fruit, sweeter fruit, more acid, ecetera? Much of the work on the impact of pesticides deals directly with the impact upon the yield and/or cosmetic affects. Is the affect more profound?

The impact on metabolic pathways has been explored by others. In a model system of cultured Nicotiana plumbaginifolia (Forlani et al., 1996) it was observed that N-substituted aminomethylene biphosphonic acid herbicide inhibited 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase of the prechorismate pathway (Shirkimate Pathway). Two herbicides (pesticides specifically for weeds), aryloxyphenoxypropionate and cyclohexanedione may inhibit the enzyme acetyl-coenzyme A carboxylase (ACCase). Herbert et al. (1996), in maize and grass, observed these inhibited fatty acid synthesis in chloroplasts. If there is no fatty acid synthesis, there is no membrane lipid production. The impact of herbicides on the chloroplasts and chlorophyll biosynthesis has also been reported (Jacobs et al., 1996). Specifically, they explored in cucumber, mustard, and radish leaves how the photobleaching diphenylether herbicides inhibited the chloroplast enzyme which converts protoporphyrinogen to protoporphyrin, an important step in the chlorophyll pathway. This inhibition takes place within the chloroplast. Not explored, was if this significantly impacted the sugar and/or starch production of the plant and fruit quality yield. Most yield studies look at total yield or the external cosmetic appearance.

Others (Webb and Hall, 1995) have shown that plant pesticides (herbicides) impact by mimicking or inhibiting auxin (plant hormone). This interest in growth, hormones and endocrine systems has been supported by the federal governments links to the endocrine disrupters project. The Endocrine Disrupters group works on the hypothesis that there are chemicals in the environment that affect endocrine systems. Some groups are particularly interested in environmental estrogens.

Although, not a direct transference to those fruits and vegetables we eat, it does give some credence that this is an interesting research endeavor. Could pesticides indirectly serve as a potential marker of quality? What is the pesticides impact upon the fruit and vegetable quality? As specifications and quality control becomes more and more precise, with the processing mostly the food scientists must be recognizant of all factors that impact the quality of the raw product.

  • References and Selected Bibliography
  • Additional Comments

  • I am interested in input, ideas, concepts, agreements, disagreements and such. If you would like to have your comments added, please send ZoeAnn Holmes, Nutrition and Food Management, Oregon State University, Corvallis, OR. and I will download it into a linked file for webbers to read.

    Students Were Asked to Comment On the Following Two Items:

  • How would you develop an experiment to "Explore the impact of pesticides on the composition and ultimate quality of fruits and vegetables."
  • -Specific goal of the project.
    -Constraints and limitations
    -Information Required
    -Treatments
    -Experimental Design and Procedures
    -Determination of Outcome
    -Other

  • Discuss briefly in class the Food Quality Protection Act
  • Comments From Student 1
  • Comments From Student 2
  • Comments From Student 3
  • Updated 3/14/97. Send mail to ZoeAnn Holmes, Nutrition and Food Management, Oregon State University, Corvallis, OR.



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