Estimates of excess risks are calculated using life-table methodology
with U.S. mortality rates, U.S. survival probabilities, and
cumulative exposures. General population risks are calculated
assuming a continuous exposure for an entire lifetime (up to a
specified age), and occupational risks are calculated assuming that the workers are exposed 8 h per day, 5 days per week, and
50 weeks per year for a period of 45 years starting at age 20.