Arsenic: Health Effects and Food Safety
Arsenic is a metallic element that is relatively abundant in the earth’s crust. It naturally occurs in the form of inorganic and organic compounds as well as a pure elemental crystal. Arsenic can be found in water, soil, air (as dust), plants, animals and many foods. All of its forms are toxic, though some experts believe that organic compounds, which mainly occur in seafood, are harmless to human health. Arsenic happens to be on the World Health Organisation’s list of 10 chemicals of major public health concern.
Arsenic is released into the environment both naturally (e.g., from volcanic eruptions, erosion of arsenic-containing minerals) and as a result of human activity (e.g., coal burning, water runoffs from industrial sites). In the past, arsenic was used in a number of industrial applications but also in agriculture as a pesticide, mainly on cotton fields and in orchards and as a feed for poultry. Today, arsenic is released into the environment mostly by burning coal in coal-fired power plants and by the smelter industry.
Drinking water is in many developing countries still the main source of exposure to arsenic. However, in the Western world, most people get exposed to this toxic chemical by eating foods contaminated with arsenic. Once in the human body, arsenic concentrates in keratin and can be easily detected in hair and nails. It leaves the body through urine (besides hair and nails).
Health Hazards of Arsenic
Although arsenic is an essential dietary trace mineral for many living organisms (including humans), in large quantities it becomes toxic. It has been associated with causing a number of health issues including skin lesions, cardiovascular disease, aplastic anemia, respiratory problems, miscarriages, low birth weight, sperm damage, neurological problems (e.g., interfering with brain development in children), diabetes and cancer (kidney, lung, skin and bladder cancers). Arsenic has been also found to interfere with the activity of testosterone and estrogen as well as certain other hormones involved in the regulation of metabolism and immune system. While the main health concern appears to be inorganic arsenic, the latest research suggests that the body can convert organic arsenic into a more toxic inorganic form.
Symptoms of arsenic toxicity depend on the type (e.g., diet, drinking water, dust) and the length of exposure as well as the type of arsenic compound. At lower levels, they usually include nausea and vomiting, reduced blood cell count and a “pins and needles” sensation in the hands and feet. At higher levels, arsenic exposure may produce breathing problems whereas long-term exposure to inorganic arsenic from drinking water may result in skin discoloration.
Arsenic in Foods
Arsenic is found in all plants and seafood. Rice, especially brown rice, and apple juice are the best known dietary sources of exposure to inorganic arsenic whereas seawater fish tends to be high in organic arsenic. Since arsenic easily dissolves in water, plants that are grown in water, such as rice, tend to have higher levels of arsenic. Besides that rice grows best in clay soil, which has more naturally occurring arsenic. Furthermore, rice grown on former cotton fields in the southern US states, which were for decades heavily sprayed with arsenic-based pesticides, is particularly high in arsenic.
When it comes to high arsenic content in apples and some other tree fruits, the problem is the widespread use of arsenic-based pesticides in orchards in the past, which still persist in the soil. However, arsenic is much more concentrated in the leaves of the plants (especially those that are rich in sulfur) than in the fruits and seeds. Therefore, certain leafy vegetables (e.g., broccoli, Brussels sprouts, cauliflower, kale and other cruciferous vegetables) tend to have high levels of arsenic.
Organic arsenic, which is naturally present in seawater, is also highly concentrated in seafood. But, many experts argue that organic arsenic is harmless because it is not retained in the body. At the moment, very little is known about the health effects of organic arsenic to counter this argument. However, recent research indicates that certain forms of organic arsenic can also be toxic to humans. In addition, other studies suggest that human metabolism can turn organic arsenic into inorganic. Dark-meat fish (e.g., bluefish, mackerel, salmon, sardines, swordfish, tuna) tend to be particularly high in arsenic. Also, dietary supplements made from seafood may have high levels of this toxic chemical.
Other products that were recently found to contain significant amounts of arsenic include beer and wine. This is due to the use of diatomaceous earth, a filtration material harboring arsenic, to clear wines and beer. Moreover, arsenic is an active ingredient in some homeopathic remedies.
Some people believe that organic foods are free of arsenic. However, plants absorb arsenic from the soil and, therefore, organic crops are not any safer than conventionally grown produce. In fact, organic rice syrup is among the foods highest in arsenic. And paradoxically, as it was mentioned above, some of the “world’s healthiest foods” such as seafood and cruciferous vegetables have the highest levels of arsenic (as well as cadmium – see this article) among all foods.