a. For non carcinogens, there is an obvious dose response relationship between their toxic effects. When they are lower than a certain dose level, they will not cause harmful effects. This dose is called "threshold". Water treatment equipment is calculated based on daily tolerable intake (TDI) when establishing limits for these chemicals.
b. Tolerable daily intake (TDI). When a certain chemical substance is ingested from food or drinking water in one's life without causing obvious health hazards, the estimated daily intake is the daily tolerance intake, which is calculated in mg/kg.
c. No harmful effect dose level (NOAEL) was observed. In the animal experimental study, the highest dose (or concentration) without any harmful effect was NOAEL. The lowest dose (or concentration) of harmful effects observed was LOAEL.
d. Uncertainty coefficient. As mentioned above, the limit value is largely determined by the data obtained from animal experiments. Obviously, there are many uncertain factors when extrapolating animal experimental data to human. In order to ensure that the established limit value of chemical substances is sufficient to protect human health, uncertainty factors should be fully considered when calculating the limit value. Therefore, the uncertainty factor is often used, which can also be understood as "safety factor", so that the established limit value has sufficient safety limits
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