Problem 1: Number of chromosomes. A human cell has 46 total or 23 pairs of chromosomes. Following mitosis, the daughter cells would each have a total of ______ chromosomes. After meiosis I, the two daughter cells would have _____chromosomes, and after meiosis II ______ chromosomes.
The permissible exposure limit (PEL or OSHA PEL) is a legal limit in the United States for exposure of an employee to a chemical substance or physical agent.For chemicals, the chemical regulation is usually expressed in parts per million (ppm), or sometimes in milligrams per cubic meter (mg/m 3). TWA is the average exposure over a specified period of time, usually a nominal eight hours. This means that, for limited periods, a worker may be exposed to concentration excursions higher than the PEL, so long as the TWA is not exceeded and any applicable excursion limit is not exceeded.
The exposure assessment is initiated by selecting the appropriate exposure limit averaging time and decision statistic for the agent. Typically the statistic for deciding acceptable exposure is chosen to be the majority (90%, 95% or 99%) of all exposures to be below the selected occupational exposure limit. Threshold limit value-Time weighted average (TLV-TWA): average exposure on the basis of a 8h/day, 40h/week work schedule.