41000 The word “toxic” is a relative term. Any chemical can be toxic to humans if administered in a large enough dose. However, in the study of toxicology, the word “toxic” usually refers to a chemical in low dose in comparison to the mass of the organism. Since the dawn of the production of synthetic organic compounds, many of these chemicals have been discovered to be deleterious to humans, plants, and animals. Synthetic organic compounds enter the environment through wastewater from industrial plants and residential homes. From there, the chemicals enter the rivers, streams, and oceans, may re-enter the atmosphere through particle formation, and eventually to food supplies through precipitation into crops and livestock. The United States Food and Drug Administration (FDA), as well as the Environmental Protection Agency (EPA), monitor the concentration of these chemicals in food and water supplies to humans. Many chemicals used on food crops have subsequently been found to be toxic to consumers. These include fertilizers, insecticides, and now the threat of deleterious gene mutations. Agricultural biotechnology has been focused on increasing crop yield and reducing crop costs through activities such as pest resistance and nitrogen fixation. It remains to be seen how novel genes and genetic manipulation of crops will affect humans in the years ahead. Many industrial workers have been exposed to deleterious chemicals since the dawn of the industrial revolution. Perhaps the most famous example is the use of asbestos in the workplace, including construction, automotive industry, and shipyards. The result of human exposure to this toxic compound is lung and respiratory disease. Recreational drug use of neurostimulators including methamphetamines, cocaine, and even nicotine may result in overdose and demise of the user. Other drugs of abuse include alcohol, marijuana, and heroin. .