[MUSIC] Hello, and welcome to this video named nutrition and contaminants in the food chain. We will talk about the basis of nutrition, the nutrients, and the contamination and bioaccumulation in the food chain. Let's talk first about the basis of nutrition. Nutrition is the science that studies the process by which living organisms acquire all the substances that they need to live and to grow. These substances are called nutrients. Nutrition has two parts, the diet and metabolism. The diet is everything that you take in, and metabolism is what happens to the food after it enters your body. Nutrition is a critical part for health and development. It is well known that better nutrition is related to improved infant, child, and maternal health, stronger immune systems, safer pregnancy and childbirth, lower risk of some diseases, and longevity. Malnutrition, in every form, presents a significant threat of human health. Today, the world is facing two faces of malnutrition, undernutrition and overweight. Elsie Widdowson was one of the first dietitians in the world. She studied the chemical composition of human bodies, but she studied also the nutritional value of essential foods. She helped the British government during the Second World War, and she gave advice to ensure that British population maintained nutritional status. Now let's talk about nutrients. There are six groups of major nutrients, carbohydrates, lipids, proteins, vitamins, minerals, and water. All these nutrients are present in food. It is estimated that 95% of our foot is directly or indirectly produced on our soils. Soil is one of the key factors for food production, and soil quality is directly linked to food quality and quantity. It is known also that poor dietary variety and consumption of crops that are poor in micronutrients are major causes of hidden hunger. And what are these elements that are essential for plant growth? There are six macronutrients and 12 micronutrients, you can see them in this slide. This food can get contaminated. It is true that contaminant levels in food are usually too low to harm consumers, but they can cause some effects such as food poisoning. Moreover, their presence or accumulation over time might affect human health. And where are these contaminants? We can find them in several places. There are, for example, natural toxins produced by fungi, algae, or plants. There are also metals and inorganic substances, such as lead and mercury. There are also unauthorized veterinary medicines. We can find out also contaminants in the environment. There are industrial chemicals that are present in air, soil, and water. And at last, we have also contaminants formed during the processing of food. Theo Colborn studied a lot these contaminants in the food. She was a professor of geology in the University of Florida. She was an environmental health analyst. And she is best known for her studies on health effects of chemicals that can disrupt our endocrine system. And now Andrea will come to talk about bioaccumulation. >> Bioaccumulation is the accumulation and enrichment of a substance, such a toxic chemical, in various tissues of a living organism, relative to that in the environment. Bioaccumulation is the net result of uptake and loss processes. For a chemical to be bioaccumulated, it must remain in the body of a living organism and has to be not easily broken down by metabolic pathways. Bioaccumulating chemicals might increase more than 5,000 times from the water to the animal. Some examples of bioaccumulating substances are organic contaminants, metals, endocrine-disrupting chemicals, or radionuclides. We have two different types of bioaccumulation processes, bioconcentration and biomagnification. Bioconcentration is the process of direct partitioning of a chemical between the water and the organism, leading to higher concentrations in the latter. Biomagnification is the result of contaminant uptake from the diet, leading to higher concentrations in the feeder than in the diet. Subsequently, the concentration of this chemical will be increased at higher position in the tropic food web. An example of bioaccumulation occurred during the massive use of DDT as insecticide during the 1950s and 1960s. DDT was first synthesized in the 1874, but it's insecticidal activity was rediscovered in the 1939. Subsequently, it was massively used during the Second World War to control malaria and typhus among troops and civilians. By 1945, DDT was readily available. And in fact, in the US, its use as agricultural and household pesticide was promoted by the government. DDT was cheap, easily to synthesize, and long-lasting. In powder form, in fact, it was four times more effective and much longer lasting than the favored method of mosquito control at the time. Scientists at the time determined that in the short-term, DDT was safe for humans. These initial experiments were done during wartime. And they were focused on the short-term or acute toxicity rather than in the long-term or chronic effects of the DDT. And they didn't focus on the ecological impacts of the DDT. However, there were concerns about its use from the very beginning. Now I will introduce the concept of half-life. Half-life is the amount of time that it takes for a half of the total amount of our chemical to degrade. And DDT has a half-life of only few days in the air, where the sunlight breaks it down. However, DDT easily becomes embedded into the fat tissues of different organisms. For example, in humans, DDT has a half-life of 6.3 years. DDT has in soils a half-life of 15 years, which means that there is a lot of time for a small organism to take in and accumulate DDT. Despite it was incredibly useful in the fight against malaria, the bioaccumulation and persistence of DDT in environment led to serious problems, health problems in many organisms. Maybe the most famous case was the decline of birds of prey in the US via actual. In few you months, more recent studies have shown that DDT might be associated with instances of cancer, infertility, miscarriage, and also diabetes. The publication of Silent Spring by Rachel Carson in 1962 forced the banning of DDT use in the USA ten years later. Carson work had a powerful impact on the environmental movement and led to the creation of the Environmental Protection Agency in this country. It was also influential on the rise of eco-feminists and also on many feminist scientists at that time. In this inspiring book, she questioned the logic of releasing potentially dangerous chemicals into the environment without even knowing the long-term consequences of their use. Rachel Carson was a marine biologist and a conservationist. She began her career in the US Bureau of Fisheries and became a full-time nature writer in the 1950s. After the publication of different bestsellers, she turn her attention into conservation, especially to some problems that she believed were caused by synthetic pesticides or biocides, as she used to call them. This resulted in the publication of Silent Spring. She passed away in 1964, only two years later the publication of Silent Spring. The second example I will explain about bioaccumulation is the case of methylmercury poisoning in Minamata Bay, Japan, during the mid-1950s. Mercury is a naturally occurring metal, and in its pure form, is not particularly toxic. However, in the bottom sediments of different water bodies, it can be transformed by bacteria into methylmercury, which is highly toxic. The problem was caused by an effluent containing methylmercury into the Minamata Bay from a chemical plant. This release of the chemical last for 40 years at least, from the 1930s until the 1970s. So methylmercury was bioaccumulated in shellfish and fish, which was even more problematic in a fishing and fish eating community. The first evidence that something was amiss came from observations of animals, for example, birds flew erratically and cats had convulsions and died. Locals started to become ill some years later in the 1960s. They had convulsions, began to stagger about, and salivated excessively. Then deaths began to occur, including newborn children. The methylmercury poisoning now, sometimes it's called Minamata disease. [MUSIC]
