This is a literature survey of chest retention of inhaled CO-60 in humans. Only the reports which followed up the retention for more than 100 days after inhalation were picked up.
The chest retention patterns reported in the literature falled into three types and none of them agreed with the ICRP lung model. Two types of chest retention have been reported in dogs which inhaled two different chemical forms of Co (i. e. C_O3O₄ and C_OO). The difference among the chest retention patterns reported in humans may be attributable to the difference of chemical form of CO inhaled.
For the convenience of the calculation of the committed dose equivalent in the lungs, one of the effective retention functions, which might not include the initial rapid clearance, was expressed as a sum of two exponentials as follows,
(chest retention)=0.53exp(-0.693t/110)+0.47exp(-0.693t/440)
The initial rapid clearance does not effectively affect the estimate of the committed dose equivalent.