A person cannot survive if their pH drops below what level?

The critical pH level for human survival is around 7.0. Below this level, the body enters a state of acidosis, which can severely disrupt metabolic processes and organs' function. When the blood pH drops to 7.0 and below, it can lead to life-threatening conditions. A pH below 6.8 is particularly perilous because it represents a significant deviation from normal physiological pH (which typically ranges from about 7.35 to 7.45).

A pH of 7.4, while ideal for many enzymatic and metabolic processes, does not reflect the threshold for survival. It is important for maintaining homeostasis but does not signify an acute survival risk. Similarly, pH levels of 6.5 are even more extreme and generally not survivable without immediate medical intervention.

In conclusion, the pH threshold at which the body can no longer maintain homeostasis and risks death is generally considered to be around 7.0, making a lower threshold like 6.8 a clear indicator of impending critical danger for the individual.