threshold

The 50 threshold separates expansion in activity from contraction.

ACA activity also tracked closely with arousal level, while ORB responded only when arousal reached a high threshold.

It also marked the eighth consecutive month below the threshold of 50, which signals a contraction in activity, while a reading above 50 indicates expansion.

The threshold is lower for some ethnic groups and people with certain weight-related health conditions.

Lead, which is associated with irreversible neurological harm, memory problems, and reduced IQ in children, exceeded the limit in 32.9% of the samples, with some measurements reaching nearly four times the accepted threshold.