Study On The Relationships Between Metals’ Health Effects And Their Background Levels And Those Between Metals’Physicochemical Properties And And Their Background Levels

Nowadays, serious environmental problems, particularly the occurring metal pollution recent years have greatly threatened human health and become a hot issue. Environmental criteria, as a matter of course, have become a key research area worldwide. It is also very urgent to do more research to improve metals’human health criteria.Human health effect of metals are related to multiple factors.Set in the very big environment background and a very long time period, with critical effect doses (NOAEL, NOAEL, BMD, and MRL) being defined to characterize the metals’human health effects, the relationships between27metals’critical effect doses and their background levels (i.e. metals’ abundances in the earth crust and in the sea) were analyzed in this study. The results showed:①Similar changing trend was observed with the metals’ critical effect doses and their continental crustal abundances, whereas there was no correlations between metals’critical effect doses and their abundance in the sea;②After logarithem, the pearson coefficient of the metal’s critical effect doses and their crustal abundances was0.4491, which is moderate correlated(0.40<r<0.79, P<0.05), and the diagnostic result was perfect;③Set Pair Analysis was used to get the connection degree (identical-discrepancy-contrary) between metals’ critical effect doses and their crustal abundances, and the identical degree part of the connection was0.7037, greater than0.6000. The result showed that metals’health thresholds shared similar changing trend, ie. Metals’health effects were closely related with their crustal abundances, which supported the correlation results. From the above, we drew conclusions:metals’toxicity or adverse effect to human beings was inversely related with their crustal abundance; when a metal’s crustal abundance is high, so is its critical effect dose level, which means the metal is relatively less toxic to human beings; otherwise, when a metal is not abundance or rare, its.critical effect dose is also relatively low, which means the metal is probably very toxic. It is easily understood that organisms have to adapt to the environment and they become more and more tolerant to elements’toxicity in order to survive. After millions of years’ transfer along the food chain, the abundance of elements in hunman body has gradually reached a relatively stable state when adapting to the environment. Therefore, when the element’s continental crust abundance is high, so is the element’s content in human body, which means the element’s toxicity is low. In addition, it can be inferred that metals’ health effect had no close relationship with their abundance in the sea because of human beings having living on the earth for millions of years. This relationship indicated the wisdom of nature seletion and the results of adaptation. However, this theory may not apply to all elements, because the toxic effects of elements also have a close relationship with their physicochemical properties, their mobility in the environment, their bioavailability and the interruption of human activities.In addition, physicochemical properties of metals were analyzed with their crustal abundance and their abundance in the sea. The results showed:①10out of the21physicochemical properties of metals were significantly related with the logarithm of their crustal abundances, ranking in the following order according to the size of the correlation coefficient (R2):covalent-bonding index (Xm2r), atom density (p), atomic number (AN), atom weight (AW), efficient nuclear charges (Z*), electronegativity (Xm), softness index (σp), electron affinities (EA), polarization force (Z*2/r) and electrochemical potential (ΔE0). Except for softness index and electrochemical potential, all the other8properties were negatively related with the logarithm of elements’crustal abundances.②The changing similarity of several properties and the logarithm of elements’crustal abundances was also proved by set pair analysis with acquiring the connection degrees as0.6333,0.6667,0.6000and0.7381.③The21physicochemical properties of metals had no correlations with their abundance in the sea. Thus we can conclude that the physicochemical property of metals was closely related with their crustal abundance.The relationship between metals’ health effect and their crustal abundance can provide references and new prospectives for environmental criteria to protect human health, and the knowledge of the influence of metals’physicochemical properties on their crustal abundance is also helpful to know more about the evolution of the earth and the elements’ abundance and to make best use of the rock and mineral resources.