Since World War II, chemical production has increased rapidly. The United States alone produces or imports 6.5438+0.9 million tons of industrial chemicals every day, drowning Americans in the ocean of synthetic products. When we talk about pollution, we think of those large factories that discharge polluted wastewater into rivers without considering these chemicals. On the contrary, they are heroes who have fulfilled the promise of "chemistry makes our life better", appearing in unbreakable baby bottles, big-screen TVs and other items. These chemicals will eventually "get rid of" from daily necessities, enter the environment, and finally enter the organism. A recent biological monitoring survey conducted by the Centers for Disease Control and Prevention (CDC) found that there are 265,438+02 trace chemicals in American environment, including toxic metals such as arsenic and cadmium, pesticides, flame retardants, and even perchlorate, a component of rocket fuel. Dr. BruceLanphear, director of Cincinnati Children's Environmental Health Center, said: "It is not the environment that is seriously polluted, but ourselves."
Now scientists can better detect the chemicals in our bodies, and they find that even a small dose of toxins will have a serious impact on our health and the future of our children. For example, bisphenol A(BPA) and phthalate esters, the main components of modern plastics, may destroy the fragile endocrine system and lead to physical development problems of teenagers. Various modern diseases such as obesity, diabetes, autism, attention deficit/hyperactivity disorder may be related to chemical products. "We didn't pay due attention to environmental exposure." Dr PhilipLandrigan, director of the Children's Environmental Health Center at Mount Sinai Medical Center in new york, said, "But people gradually realize that children are particularly vulnerable to environmental hazards."
Low dose threat
His original name was Phillips? Aurioles? Deo Frest? Bohm Busz? Feng? Philip Aurelius Theo Fielas Bumstos von Hengheim, his contemporaries called him Parra Celsus, while science students called him "the father of toxicology". This Swiss doctor took the lead in using chemicals in medicine in the16th century. His famous saying "dose leads to toxicity"-even toxic substances can be safe as long as the dose is kept below a certain level-is still the basic principle of modern toxicology.
This helps to explain why industrial chemicals have never been subject to strict supervision and management like drugs and pesticides. Even if the chemicals used to help make plastic bottles can penetrate into the human body, the general idea is that its dosage will be very low and will not do any harm to the human body. However, with the improvement of biological monitoring technology-we can now detect the human exposure level as small as one trillion, which is equivalent to one twentieth of a drop of water in an Olympic standard swimming pool-scientists have found that the chemicals carried in the human body far exceed our previous understanding.
At the same time, scientists have learned that some toxins may be harmful to people even at very low exposure levels. The exposure limit of lead, which is considered to be safe, will directly reduce people's IQ, from 60 micrograms per 100 milliliters of blood in 1970 to 10 micrograms today. Some chemicals, such as bisphenol A, may have unusual effects on human body even at very low doses. Bisphenol A, invented in 189 1, has been used to harden polycarbonate plastics and produce epoxy resin since the 1940s, and the latter is used for the lining of food and beverage containers. Polycarbonate can be identified by the recycling mark "7" at the bottom of the plastic bottle. Other plastic components, including potentially harmful types, can also be identified by recycling labels. These recycling marks are also called synthetic resin identification codes.
Bisphenol A has a wide range of uses, and now the world produces 2.7 million tons of bisphenol A every year. But the problem is that bisphenol A is also a synthetic estrogen, and plastic products containing bisphenol A will break, especially when these plastic products are washed, heated or applied with external force, which will make bisphenol A penetrate into food and water, and then enter the human body. Almost everyone will encounter this situation. According to a survey conducted by the Centers for Disease Control and Prevention, 93% of Americans over 6 years old have found bisphenol A in their urine. If you don't have bisphenol A, you don't live in the modern world at all.
However, the content of bisphenol A in urine detected in this survey is far below the safety threshold of 50 micrograms per kilogram of body weight per day recommended by relevant American institutions. However, this proposal was put forward 22 years ago. Since then, scientists have learned more about the effects of bisphenol A, even in small doses. From 65438 to 0998, Patricia Hunt, a geneticist at Washington State University, found that female mice injected with bisphenol A had serious reproductive problems, including producing defective eggs. Recently, she published a research report, which showed that the offspring of mice exposed to bisphenol A during pregnancy would produce defective eggs, which would bring trouble to the offspring. "This is a powerful role," Hunter said. "One exposure harms three generations."
As a synthetic estrogen, bisphenol A can play a role similar to hormones. Hormone is a powerful chemical substance, including testosterone and adrenaline, which can regulate the human body. Trace hormones can cause great biological and behavioral changes in the human body, so chemicals similar to some hormones can also play the same role, especially in the critical period of a person's development, such as the first three months of pregnancy. Children are particularly exposed to chemicals, not only because their bodies develop rapidly, but also because they eat more and drink more than adults relative to their weight. ) This was discovered by dozens of scientists in animal experiments. Exposure of rodent fetuses to bisphenol A can lead to diseases ranging from breast cancer to male reproductive defects and even neurobehavioral problems.
Bisphenol A is not the only industrial chemical used in daily life that may cause endocrine system disorder. A phthalate used to soften PVC plastics can be found in shower curtains, cosmetics and intravenous bags. It has been proved that it can disturb the hormones of animals and is related to the decrease of sperm count and other female characteristics in male mice. Similarly, PBDEs are very stable flame retardants in the environment and can be used to produce electronic products, polyurethane foams and other plastics. Now this substance has been eliminated. (PBDEs can stay in the body for many years. Bisphenol A and phthalate esters will be excreted in a day or two, but their universality means that we are exposed to them almost every day. )
Although there are few studies on human endocrine disruptors compared with animals, the studies that have been done have begun to show worrying correlation. High doses of phthalates and other endocrine disruptors have been proved to be related to the early development of girls' breasts, which is a risk factor for breast cancer. Endocrine disruptors are also suspected to be related to the increase of hypospadias, which is a corrective deformity of boys' urethra. Shanna Swan, director of the Center for Reproductive Epidemiology at the University of Rochester in the United States, found in 2008 that boys who were exposed to phthalates during the fetal period were more likely to have genital malformations such as testicular and penile failure. "I'm worried about what will happen to these children when they grow up and whether they will have fertility problems," Swan said. "We are trying to find the answer together."
The scientific problems surrounding endocrine disruptors are far from being solved. Although some studies, such as Dr. Swan's, show that exposure to phthalates is related to developmental defects, this does not mean that chemicals will cause this problem. Defenders of the chemical industry point out that the level of human exposure to bisphenol A and phthalates is still far below the safety level set by the government; Health institutions around the world also believe that chemicals are safe for human beings. Moreover, some peer-reviewed studies have not proved that endocrine disruptors such as BPA are necessarily related to physical defects. "I think the research results of [bisphenol A] have come out," said RichardSharpe, a researcher at the Reproductive Biology Center of Queen's Medical College in Edinburgh, England. "If you limit this problem to the effect on estrogen, I don't find such a problem."
However, scientists' knowledge has gradually moved away from the view that bisphenol A is completely safe. When researchers started warning about BPA in the late 1990s, they were still in the minority. During the Bush administration, the US Food and Drug Administration reviewed bisphenol A and ruled that it was safe. However, the agency's own scientific review committee criticized the report for relying almost entirely on research funded by the chemical industry. In 2008, Canada ruled that it was unsafe for babies to be exposed to bisphenol A and banned the use of this chemical in baby bottles. Later, many American states and large retailers, including Wal-Mart, took the same measures. Although European regulators declared bisphenol A safe in an assessment in 2008, Denmark banned the use of bisphenol A in baby bottles last month.
In 2009, the International Endocrinology Society issued a statement declaring that endocrine disruptors are a major public health problem and calling on the government to strengthen supervision to reduce human exposure. Even the attitude of the US Food and Drug Administration has changed: this year 1 month, when the Obama administration launched a $30 million BPA research program, the agency expressed "some concerns" about BPA. Dr JoshuaSharfstein, chief deputy Commissioner of the US Food and Drug Administration, told reporters at the time: "Especially considering that children are exposed to bisphenol A everywhere in the early stages of development, these data and studies deserve close attention."
solution
One model may be the Regulation on Registration, Evaluation, Authorization and Restriction of Chemicals implemented by the European Union. The law shifts the burden of proof to the chemical industry, requiring chemical production enterprises to prove that their products are harmless to human health or the environment, and any chemical production that is highly concerned must obtain special authorization. The chemical industry in the United States has reservations about implementing the REACH-like Act in the United States on the grounds of cost, but this change in management may be a long-awaited safety measure. Richard Denison, a senior scientist at the American Environmental Protection Foundation, said: "If we can apply the measures we have taken in pesticide and drug management to chemical management, it will bring great changes."
Another solution may rely on the new concept of "green chemistry": chemicals minimize the risks that may lead to danger from the beginning. Facts speak plainer than words. Green chemistry aims to put aside disputes and develop chemical products that are not only completely non-toxic, but also leave no dangerous residues and use less energy. The US Environmental Protection Agency's "Presidential Green Chemistry Challenge Award" recognizes the achievements of sustainable chemical design, such as making cosmetics through a new biocatalytic process without using toxic solvents. At the annual meeting of the American Chemical Society, 12000 people attended, and 1600 people devoted themselves to the sustainable development of the chemical industry. "In the future, all chemicals will be green," said John Warner, director of the Warner babcock Institute of Green Chemistry. "In that world, we will no longer need supervision."
However, even Warner admits that such a day is far from us. At the same time, we need to know how determined we are to become such a society. "Science is more than just data," said birnbaum of the National Institute of Environmental Health. "It is an interpretation of the data." This explanation will not be made by scientists in the end, but depends on us. Earth Day, which started 40 years ago, was a great success because it aroused people's excitement. The question now is whether we will bring the same stimulus to the equally intangible but possibly equally dangerous environmental threats. (Bioon.com Biology Valley)