(China Geo University, Beijing, 100083)
The quality of drinking water is closely related to people's health. Drinking water quality is also an important indicator of environmental quality. At present, most scholars recognize that the main endemic diseases related to the environment are Keshan disease, Kaschin-Beck disease, endemic goiter and cretinism, endemic fluorosis and endemic arsenic poisoning. Most of the above endemic diseases are directly related to the soil and water environment in the ward, especially to the quality of groundwater.
1 Keshan epidemic
Keshan disease is a kind of nonspecific cardiomyopathy with myocardial lesion and myocardial necrosis as the main symptoms, also known as idiopathic myocardial hypertrophy. /kloc-0 In the winter of 935, an acute epidemic occurred in Keshan County, Heilongjiang Province, causing a large number of deaths, which attracted attention. Because the cause is unknown, it is called "Keshan disease". In the following decades, the disease was found in 16 provinces and regions in China. From the geographical distribution, the disease is generally distributed in the northeast-southwest direction, starting from Heilongjiang Province in the Dadaling and Xiaoxing 'anling Mountains in the northeast, and reaching the mouth of Lancang River in Hengduan Mountains and Yarlung Zangbo River in Tibet in the southwest, which has obvious regional characteristics.
There are two views about the cause of this disease:
(1) According to the theory of biological etiology, it is considered that the disease is caused by some pathogenic microorganism, especially virus infection.
(2) Abiotic causes, usually called the causes of soil and water, can be divided into two types: ① toxic factors, mainly referring to nitrite or some organic substances contained in the environment; ② Element deficiency factors mainly refer to selenium deficiency, molybdenum deficiency or magnesium deficiency. Especially, the influence of low selenium environment has received the most extensive attention. It has been proved that there is a low selenium ecological zone in China, which is basically consistent with the distribution of most Keshan endemic areas. Therefore, most scholars believe that low selenium in the environment is one of the important factors of Keshan disease, and the application of sodium selenite (Na2SeO3) has achieved remarkable results in prevention.
But some wards cannot be simply explained by selenium deficiency. For example, as reported by the Keshan Disease Prevention and Control Institute in Chuxiong, Yunnan Province, the selenium content in soil, grain, human hair and blood in Zhaotong, an endemic area of Keshan disease in this province, is equivalent to that in non-endemic areas, and it is considered that the incidence has little to do with selenium level; Although Maoergai, Kalong and other places in Sichuan Province belong to low selenium areas, Keshan disease has not occurred. According to the report of the Institute of Endemic Disease Prevention and Control in Zhangjiakou City, Hebei Province, the selenium content in plant food in Keshan disease area in this area is higher than that in the corresponding samples of major disease areas in China, and there is no obvious difference between them. However, it is found that the magnesium content in drinking water (groundwater) in the disease area is obviously lower than that in the non-disease area, and the groundwater is soft or extremely soft, so it is considered that the disease area is mainly caused by magnesium deficiency. Through animal (rat) control test, all animals were prevented by magnesium, but no myocardial injury was found. On the basis of this study, a certain amount of magnesium (MgCl2) was added to the drinking water in the ward. After long-term observation of the preventive effect, the cure rate of Keshan disease patients reached 66.7%, indicating the role of magnesium in the prevention and treatment of Keshan disease.
We pay attention to the relationship between the contents of magnesium and chromium in groundwater (as drinking water) and the incidence of coronary heart disease (coronary atherosclerotic cardiomyopathy) in a certain place. The study area is Yuncheng Basin in Shanxi Province, and the famous Yuncheng Salt Lake is located in its south. The contents of Mg2+ and Cr3+ in thousands of square kilometers of groundwater in this area are relatively high. The contents of Mg2+ in shallow quaternary water (about 60m) are about 440mg/L, Ca2+ 170mg/L, and the contents of Mg2+ in deep quaternary water (about 300m) are about 55mg. Coincidentally, medical researchers at Yuncheng People's Hospital found that the incidence of coronary heart disease in this area may be the lowest in China. Compared with some cities or regions in China, the incidence of coronary heart disease is 6.3 1% ~ 17.2%, which is 6.46% in the whole country and only 1.4 1% in Yuncheng area. The reasons for it were not known We believe that the low incidence of coronary heart disease in Yuncheng area is related to the abundance of geochemical elements in the water and soil environment in this area. Schroeder, a famous American doctor of medicine, once pointed out that the mortality of coronary heart disease in North America is high, the content of Cr in human tissues is low, the mortality of coronary heart disease in Africa is low, and the content of Cr in human tissues is high, indicating that Cr is negatively correlated with the mortality of coronary heart disease. Therefore, we believe that there are still many problems worthy of in-depth discussion, whether it is Keshan disease or cardiomyopathy in other areas, due to the particularity of their geochemical environment.
2. Kong Di's disease.
Kaschin-Beck disease is mainly distributed in Heilongjiang, Jilin, Liaoning and other provinces 15, and it has been found in more than 300 counties. The disease has also been reported in Siberia, Russia and mountainous areas in northern Korea. In China, the disease is mainly distributed in the broadband area extending from northeast to southwest, and it is more common in mountainous areas, hills and areas that transition to the plain. It is somewhat similar to Keshan disease, so some people call it sister disease.
The disease is mainly distributed in low selenium areas, and the selenium content in drinking water, soil and grain in the ward is obviously low, and the population in the ward is in a state of low selenium nutrition. Supplementing selenium (sodium selenite tablets) in the population has achieved satisfactory results. However, some people think that besides the low selenium environment, there are other environmental factors that are co-pathogenic with selenium deficiency.
Drinking water contains organic compounds and Fusarium toxins. Drinking water in most wards is rich in organic matter (humic acid) and minerals.
Some studies believe that the pathogenic factors mainly enter the human body through the food produced in the ward. Microbiological examination found that the food in the ward was seriously infected by Fusarium.
3. Endemic hypothyroidism and cretinism.
Endemic goiter, referred to as goiter for short, commonly known as big neck disease, is called "scabies" in China ancient books. It is one of the oldest diseases in human beings and spreads all over the world. It is mainly caused by elemental iodine deficiency in the environment. When the iodine content in drinking water is less than 5 μ g/L (5ppb), the incidence of endemic cretinism is very high. The next generation of endemic cretinism patients may be endemic cretinism patients, whose main manifestations are dullness, short stature and deafness.
Endemic onychomycosis is widely distributed in China. Except for Shanghai, other provinces, autonomous regions and municipalities directly under the Central Government are prevalent to varying degrees. The basic characteristics of its distribution are that mountains are more than hills and hills are more than plains, which is related to the easy leaching of iodine and the hydrogeochemical characteristics of iodine.
In limestone areas, drinking water is calcium bicarbonate water. Although iodized salt is supplied, calcium and iodine form insoluble compound calcium iodide Ca(I5O3)2, which may inhibit the effective absorption of iodine by human body. It seems that there is still a problem of iodine bioavailability in the prevention and treatment of endemic goiter in limestone areas. Since the 1970s, iodine-induced goiter has been found in some provinces and regions of China. Some people call it iodine-excess goiter, mainly because of the high iodine content in groundwater as drinking water, some of which are as high as several hundred micrograms of iodine per liter, even exceeding 65,438 0000 micrograms per liter ... So far, it has been found in Kuitun, Xinjiang, Xiaoyi, Shanxi (mountain basin), Bohai Bay, Guhuanghekou Plain, Shandong, and the central and eastern parts of North China Plain.
According to our water samples from more than 60 shallow wells in Feixiang, Guangping, Jize, Yongnian and Guantao counties in the east of Handan, the iodine content ranges from tens of micrograms to 600 micrograms/liter. For example, according to the investigation of the local health department, the incidence rates of middle schools and primary schools in Cui Zhuang, Feixiang County are as high as 45.5% and 42.8% respectively, which has greatly exceeded the threshold of 5% epidemic. We specially determined the composition of the drinking water well in the village. The results show that the iodine content is 65438 055 μ g/L, the total hardness is 585.5mg/L (calculated by CaCO3), the total dissolved solids are 947 mg/L, the content of SR2 is 3.97 mg/L, the fluorine content is 0.83 mg/L, and the pH value is 7.29. The iodine content of well water in Cunnan is 240μg/L, and other components are similar.
This leads to two other problems. First, is the upper limit of drinking water iodine prevalence 200 ~ 300μ g/L or lower? What is appropriate content? Another question is, will alkaline earth metals such as calcium, magnesium and strontium interfere with the absorption of iodine? These are all worthy of in-depth study.
It seems that while paying great attention to the influence of iodine deficiency goiter and proper iodine supplementation on children's intellectual growth and development, we should also strengthen the research on goiter caused by drinking water with high iodine.
Endemic fluorosis (endemic fluorosis)
Endemic fluorosis is also an ancient endemic disease, which is caused by excessive intake of elemental fluorine, ranging from dental fluorosis (mottled enamel teeth) to skeletal fluorosis, and even loss of working ability. This endemic disease is widely distributed in the world, covering more than 40 countries on five continents. It is prevalent in 20 provinces and regions of China to varying degrees, especially in the north, but scattered in the south. It is estimated that about 700-800 million people are threatened by fluorosis. The endemic fluorosis in China is mainly drinking water, and the prevalence of fluorosis has a good correlation with the fluorine content in drinking water. Generally speaking, the higher the fluorine content in drinking water (China stipulates that the fluorine content in drinking water shall not exceed 1mg/L), the longer the drinking time, the more serious the illness will be. In the arid and semi-arid areas of northern China, groundwater is an important or only water supply source, and both shallow groundwater and deep groundwater contain too much fluorine.
Although the general rule is that the incidence of endemic fluorosis tends to increase with the increase of fluorine content in drinking water (groundwater), the abnormal phenomena of "low incidence (referring to skeletal fluorosis)" and "high fluorine and low incidence" have been found in some areas. According to our investigation, the fluorine content of groundwater in villages with high incidence of skeletal fluorosis in Linzhang County, Hebei Province is1.2 ~ 2.0 mg/L; On the contrary, in some villages where the fluorine content in groundwater is as high as 2.4 ~ 2.8 mg/L, there are no cases of skeletal fluorosis or the incidence rate is extremely low. This anomaly was also found in Heshun area in central Shanxi. The fluorine content in drinking water in Heshun area is generally lower than 1mg/L, with an average of 0.2 ~ 0.3 mg/L. It belongs to the low fluorine water area in the north, and the fluorine content in grain in this area is not high either, but the incidence of "skeletal fluorosis" is surprisingly high, reaching 69.4%.
According to our investigation in some counties in southern Hebei Province, it is found that the content of toxic trace element beryllium (lithophile and osteophilic) in groundwater in fluorosis areas is relatively high, reaching (4 ~ 15) × 10-9. At present, the drinking water standard stipulated by the Soviet Union and the Federal Republic of Germany is 0.2× 10-9, which is dozens of times different. It is said that there is a kind of "beryllium rickets", which is similar to rickets in skeletal fluorosis. Is it because of beryllium poisoning? Or is it complicated with fluorosis? It is worth further discussion.
Endemic arsenic poisoning.
Compared with the above endemic diseases, it can be said that it is an endemic disease that has not been discovered for a long time, and it is a chronic arsenic poisoning disease caused by excessive intake of arsenic in the environment (arsenic As2O3 is an important arsenic-containing mineral).
Up to now, most endemic arsenic poisoning found at home and abroad is caused by high arsenic content in drinking water sources. China stipulates that the arsenic content in drinking water should not exceed 0.05mg/L, and some people are poisoned by burning high arsenic coal (Guizhou). For example, the arsenic content in well water in Cordoba, Argentina is 0.9 ~ 3.4 mg/L, and there are high arsenic water in parts of northern Mexico, Antofagasta, Chile and Japan. 1989 arsenic poisoning was found in southern Thailand, and the arsenic in shallow groundwater was as high as 9 mg/l; The arsenic poisoning area in India was also discovered in 1987, covering an area of 3.4× 104km2, and1000000 people had symptoms of drinking water arsenic poisoning. At present, the number of arsenic poisoning is increasing at the rate of 10% per year (Challrabatyetal,1987; Aswathanarayana， 1997).
Endemic arsenic poisoning was discovered late in China. In the 1960s, Taiwan Province Province reported that some areas along the southwest coast of the island, such as Yi and Tainan County, were statistically called "black foot disease", which eventually led to ulceration and gangrene. Since then, many scholars have studied it. According to Professor Lv Fengzhou from the Medical College of Taiwan Province Provincial University (1994). The first symposium on cross-strait resources and environmental geochemistry reported that the arsenic content in well water in this area was 0.85 ~ 2.5 mg/L, and the incidence of skin cancer reached 10.6%. It is also found that there are "fluorescent substances" in well water, that is, "humic substances". The biological toxicity of "fluorescent substance" has been confirmed by aquatic animal experiments, so it is considered that it is closely related not only to the etiology of blackfoot disease, but also to the etiology of cancer and other endemic diseases.
The disease was first discovered in Kuitun area of northern Chinese mainland in the early 1980s. The arsenic content in well water is 0.1~ 0.85 mg/l; During 1992, arsenic poisoning was found in Hetao area of Inner Mongolia. So far, the population of the epidemic area is about 300,000. During the period of 1994, it was found that nine towns in Shanyin County and Yingxian County of Datong Basin in Shanxi Province were chronic arsenic poisoning areas with a population of 60,000, which was also caused by drinking well water with high arsenic content for a long time. For example, the arsenic content in the shallow groundwater in Caicun, Shanyin County is 0.075 ~ 4.435 mg/L. The special symptoms of arsenic poisoning are abnormal skin pigment, hyperkeratosis and skin thickening, which often occur in the palms of hands, feet and other parts.
The main endemic diseases and drinking water quality in China may be related to some unknown pathogenic factors or pathogenic composite factors, which urges researchers to follow up the research for the benefit of the people in local endemic areas.
refer to
[1] Atlas of Endemic Diseases and Environment in People's Republic of China (PRC). Editorial Committee of Atlas of Endemic Diseases and Environment in People's Republic of China (PRC). Science press, 1989.
[2] Song, et al. Environmental Medicine. Tianjin Science and Technology Press, 1987.
Shen et al. Foundation of hydrogeochemistry. Geological publishing house, 1993.