Z77.121Contact with and (suspected) exposure to harmful algae and algae toxins

Z77.121 is the ICD-10-CM diagnosis code for contact with and (suspected) exposure to harmful algae and algae toxins. It belongs to category Z77 (other contact with and (suspected) exposures hazardous to health), block Z77-Z99 (persons with potential health hazards related to family and personal history and certain conditions influencing health status) and chapter 21 (factors influencing health status and contact with health services). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within Z77.12 (contact with and (suspected) exposure to hazards in the physical environment), Z77.121 is specifically for contact with and (suspected) exposure to harmful algae and algae toxins. Related codes cover mold (toxic) (Z77.120), noise (Z77.122), radon and other naturally occurring radiation (Z77.123) and other hazards in the physical environment (Z77.128).

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 951 (Other Factors Influencing Health Status, relative weight 0.5577), in MDC 23 (Factors Influencing Health Status and Other Contacts with Health Services), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It is not acceptable as the principal diagnosis for an inpatient stay; it may be reported as a secondary diagnosis.

It is exempt from present-on-admission (POA) reporting, so no POA indicator is required.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as V87.32 (contact with and (suspected) exposure to algae bloom).