2024 ICD-10-CM Diagnosis Code Z77.121

Contact with and (suspected) exposure to harmful algae and algae toxins

ICD-10-CM Code:
Z77.121
ICD-10 Code for:
Contact w and exposure to harmful algae and algae toxins
Is Billable?
Yes - Valid for Submission
Code Navigator:

Code Classification

  • Factors influencing health status and contact with health services
    (Z00–Z99)
    • Persons with potential health hazards related to family and personal history and certain conditions influencing health status
      (Z77-Z99)
      • Other contact with and exposures hazardous to health (Z77)
        (suspected)

Z77.121 is a billable diagnosis code used to specify a medical diagnosis of contact with and (suspected) exposure to harmful algae and algae toxins. The code is valid during the current fiscal year for the submission of HIPAA-covered transactions from October 01, 2023 through September 30, 2024. The code is exempt from present on admission (POA) reporting for inpatient admissions to general acute care hospitals.

This code describes a circumstance which influences the patient's health status but not a current illness or injury. The code is unacceptable as a principal diagnosis.

Approximate Synonyms

The following clinical terms are approximate synonyms or lay terms that might be used to identify the correct diagnosis code:

  • Dermatosis due to algae

Clinical Classification

Tabular List of Diseases and Injuries

The following annotation back-references are applicable to this diagnosis code. The Tabular List of Diseases and Injuries is a list of ICD-10-CM codes, organized "head to toe" into chapters and sections with coding notes and guidance for inclusions, exclusions, descriptions and more.


Inclusion Terms

Inclusion Terms
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.
  • Contact with and (suspected) exposure to (harmful) algae bloom NOS
  • Contact with and (suspected) exposure to blue-green algae bloom
  • Contact with and (suspected) exposure to brown tide
  • Contact with and (suspected) exposure to cyanobacteria bloom
  • Contact with and (suspected) exposure to Florida red tide
  • Contact with and (suspected) exposure to pfiesteria piscicida
  • Contact with and (suspected) exposure to red tide

Index to Diseases and Injuries References

The following annotation back-references for this diagnosis code are found in the injuries and diseases index. The Index to Diseases and Injuries is an alphabetical listing of medical terms, with each term mapped to one or more ICD-10-CM code(s).

Code Edits

The Medicare Code Editor (MCE) detects and reports errors in the coding of claims data. The following ICD-10-CM Code Edits are applicable to this code:

  • Unacceptable principal diagnosis - There are selected codes that describe a circumstance which influences an individual's health status but not a current illness or injury, or codes that are not specific manifestations but may be due to an underlying cause. These codes are considered unacceptable as a principal diagnosis.

Present on Admission (POA)

Z77.121 is exempt from POA reporting - The Present on Admission (POA) indicator is used for diagnosis codes included in claims involving inpatient admissions to general acute care hospitals. POA indicators must be reported to CMS on each claim to facilitate the grouping of diagnoses codes into the proper Diagnostic Related Groups (DRG). CMS publishes a listing of specific diagnosis codes that are exempt from the POA reporting requirement. Review other POA exempt codes here.

CMS POA Indicator Options and Definitions

POA IndicatorReason for CodeCMS will pay the CC/MCC DRG?
YDiagnosis was present at time of inpatient admission.YES
NDiagnosis was not present at time of inpatient admission.NO
UDocumentation insufficient to determine if the condition was present at the time of inpatient admission.NO
WClinically undetermined - unable to clinically determine whether the condition was present at the time of inpatient admission.YES
1Unreported/Not used - Exempt from POA reporting. NO

Convert Z77.121 to ICD-9-CM

  • ICD-9-CM Code: V87.32 - Contact/exp algae bloom
    Approximate Flag - The approximate mapping means there is not an exact match between the ICD-10 and ICD-9 codes and the mapped code is not a precise representation of the original code.

Patient Education


Water Pollution

We all need clean water. People need it to grow crops and to operate factories, and for drinking and recreation. Fish and wildlife depend on it to survive.

Many different pollutants can harm our rivers, streams, lakes, and oceans. The three most common are soil, nutrients, and bacteria. Rain washes soil into streams and rivers. The soil can kill tiny animals and fish eggs. It can clog the gills of fish and block light, causing plants to die. Nutrients, often from fertilizers, cause problems in lakes, ponds, and reservoirs. Nitrogen and phosphorus make algae grow and can turn water green. Bacteria, often from sewage spills, can pollute fresh or salt water.

You can help protect your water supply:

  • Don't pour household products such as cleansers, beauty products, medicines, auto fluids, paint, and lawn care products down the drain. Take them to a hazardous waste collection site.
  • Throw away excess household grease (meat fats, lard, cooking oil, shortening, butter, margarine, etc.) diapers, condoms, and personal hygiene products in the garbage can.
  • Clean up after your pets. Pet waste contains nutrients and germs.

Environmental Protection Agency


[Learn More in MedlinePlus]

Code History

  • FY 2024 - No Change, effective from 10/1/2023 through 9/30/2024
  • FY 2023 - No Change, effective from 10/1/2022 through 9/30/2023
  • FY 2022 - No Change, effective from 10/1/2021 through 9/30/2022
  • FY 2021 - No Change, effective from 10/1/2020 through 9/30/2021
  • FY 2020 - No Change, effective from 10/1/2019 through 9/30/2020
  • FY 2019 - No Change, effective from 10/1/2018 through 9/30/2019
  • FY 2018 - No Change, effective from 10/1/2017 through 9/30/2018
  • FY 2017 - No Change, effective from 10/1/2016 through 9/30/2017
  • FY 2016 - New Code, effective from 10/1/2015 through 9/30/2016. This was the first year ICD-10-CM was implemented into the HIPAA code set.