ICD-10-CM 2027
ICD-10 code for algae bloom contact
Contact with and (suspected) exposure to harmful algae and algae toxins
From the official ICD-10-CM alphabetic index entry “Contact (with) › algae bloom”. Page updated September 29, 2026.
About coding algae bloom contact
The ICD-10-CM code for algae bloom contact is Z77.121 (Contact with and (suspected) exposure to harmful algae and algae toxins).
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.
Common questions about algae bloom contact ICD-10 codes
What is the ICD-10 code for algae bloom contact?
- Z77.121 — Contact with and (suspected) exposure to harmful algae and algae toxins.
Is Z77.121 billable?
- Yes. Z77.121 is a billable/specific ICD-10-CM code valid for FY2027 (October 1, 2026 – September 30, 2027).
Can Z77.121 be used as a principal diagnosis?
- No. It is not acceptable as the principal diagnosis for an inpatient stay; it may be reported as a secondary diagnosis.
Is Z77.121 a CC or MCC?
- No. Z77.121 is neither a CC nor an MCC under MS-DRG v44.0.