Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals, published by the National Environmental Health Association, 2026.
Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
October, 2025
Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
Acknowledgments Primary Authors Justin Andrew Gerding, MPH, DHA, REHS, CPH, DAAS Gina Bare, MA, RN, National Environmental Health Association David Dyjack, DrPH, CIH, National Environmental Health Association Acknowledgments The authors gratefully acknowledge the subject matter experts who participated in reviewing and providing feedback for this document. AI Disclaimer The authors used generative AI tools to assist with copyediting, including grammar, spelling, and readability and flow improvements. All outputs were reviewed and verified by the authors. Funding Acknowledgment This project is one of several projects supported by the Centers for Disease Control and Prevention (CDC) of the U.S. Department of Health and Human Services (HHS) as part of a financial assistance award totaling $300,000 with 100% funded by CDC/HHS. The contents are those of the author(s) and do not necessarily represent the official views of, nor an endorsement by, CDC/HHS, or the U.S. government.
Recommended Citation: Gerding, A.J., Bare, G., & Dyjack, D. (2026). Responding to indoor mold concerns: A resource for environmental public health professionals. National Environmental Health Association. https://pubs.neha.org/indoor-mold-concerns
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
Overview Environmental public health (EPH) professionals commonly respond to mold concerns in homes, schools, workplaces, and other community settings. This resource supports those responses across diverse indoor environments, including during emergencies and disaster recovery. It complements existing guidance from governmental, nongovernmental, and academic partners and provides practical, field-based tools aligned with three core activities: assess, consult, and communicate. The rapid-response guidance highlights key considerations for these activities (Table 1). Although each topic is covered in greater detail elsewhere in this document and other basic topics about mold are covered in Appendix A, this resource serves as a concise, field-ready reference for EPH professionals. It can support timely responses to indoor mold concerns during emergencies and other time-sensitive situations, helping to guide and inform immediate actions.
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
Table 1. Rapid-Response Guidance for Responding to Indoor Mold Concerns
1. CONDUCT OR SUPPORT INDOOR MOLD ASSESSMENTS
2. CONSULT ON REMEDIATION AND MOLD CLEANUP ACTIONS
3. COMMUNICATE FINDINGS, GUIDANCE, AND HEALTH RISK INFORMATION
Determine need, responsibility, or authority to conduct or support an indoor assessment, while taking into consideration facility or building type and occupancy, including special populations. Identify applicable regulatory requirements or laws addressing mold and sanitation, depending on facility type. Conduct or support indoor assessments to understand water and moisture sources (e.g., flooding, leaks) and if mold growth has occurred. Observe mold growth, moisture presence, water sources, and humidity.
Recommend fixing roof or plumbing leaks, and other structural deficiencies leading to water intrusion or moisture and maintaining indoor humidity between 30% and 50%. Suggest cleaning hard surfaces using a detergent and water. Recommend considering use of mold-killing chemical products, including a solution of no more than 1 cup of household laundry bleach in 1 gallon of water. Encourage drying water-damaged materials within 24–48 hr. Consider discarding items that remain wet beyond this period, especially porous materials (e.g., carpets, upholstery, fabrics), and if the water or moisture source might contain fecal contamination, hazardous chemicals, or other contaminants. Recommend wearing personal protective equipment (PPE), including long gloves and eye protection. Use an N95 respirator to avoid breathing in mold or mold spores during cleanup (requires fit-testing in occupational settings). Suggest contacting a remediation contractor if mold- contaminated areas are >10 ft².
Report assessment findings and provide guidance and answer questions about remediation, cleanup, and potential exposure risks and health effects.
Establish key messages while considering language, cultural, and literacy needs and disseminate communications using a variety of media and channels, including digital platforms and social media. Coordinate communication efforts during emergency response operations.
Escalate requests for assistance in complex situations such as disasters with widespread community impacts or special populations with increased health risks.
Make referrals to government agencies that could provide resources for remediation and cleanup.
Consider conducting a verification survey to ensure indoor mold and moisture issues have been successfully resolved following remediation and cleanup.
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
Acknowledgments ............................................................................................... i Overview ........................................................................................................... ii 1. Introduction .................................................................................................... 1 2. Background .................................................................................................... 2 3. Roles and Responsibilities ................................................................................ 4 4. Practive-Based Guidance ................................................................................. 6 5. Frequently Asked Questions (FAQs) ................................................................ 10 6. References . .................................................................................................. 14 Appendix A. Comprehensive Guidance and Training ............................................. 15 Appendix B: Indoor Mold Assessment Form ......................................................... 17 Appendix C: Inspection and Investigation Toolkit Items ......................................... 19 Appendix D: Post-Remediation Verification Checklist ........................................... 20 Appendix E: Safety Considerations for Indoor Assessments .................................. 21 Appendix F: Example Email Response to Requests or Inquiries .............................. 22 Appendix G: Key Messages and Discussion Points ............................................... 23 Appendix H. Example Emergency Response Communications Plan ........................ 24 Appendix I: Example Social Media Messages ....................................................... 25 Contents
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
1. Introduction EPH professionals commonly receive requests for assistance with mold concerns in homes, public buildings, and commercial facilities, including after community-wide impacts from natural disasters or extreme weather. Comprehensive guidance on indoor moisture and mold exists; however, this practical, applied resource is tailored specifically to EPH professionals. It provides EPH professionals with: • Information for responding to mold-related inquiries, concerns, complaints, and requests for technical assistance. • Tools to support assessments and field investigations, decision- making, and communication with homeowners, building managers, and community members. • Links to existing comprehensive guidance offering detailed technical information on key topics and best practices for addressing moisture and mold in indoor environments. This resource also aligns with NEHA's Pillars of Governmental Environmental Public Health: A Guide to Scalable Environmental Public Health Programs , which identifies air quality as a secondary program area within local EPH departments and recognizes indoor mold and moisture as concerns within its scope (Bare et al., 2025). 1.1 Scope This resource provides practical guidance that complements existing governmental, nongovernmental, and academic resources. While not exhaustive, it offers field-oriented information and tools primarily for EPH professionals working in public health agencies. The scope of this guide is limited to indoor moisture and mold and does not address bacteria, viruses, or other biological, chemical, or physical hazards associated with the indoor environment. The guidance can be applied across a variety of settings, including homes, schools, long-term care facilities, and disaster-affected communities. It places, however, greater emphasis on residential settings, since mold in homes is typically a primary source of requests and complaints.
Additionally, this resource supports EPH professional responsibilities including assessment, consultation, and information-sharing activities rather than actual remediation and cleanup actions, which public health agencies do not perform. The Frequently Asked Questions (FAQs) section provides information to address questions and concerns from homeowners and residents, community members, and building or
facility managers and occupants. 1.2 Special Populations
Groups that may be especially susceptible to the health effects of mold exposure include infants and young children, older adults, people with respiratory conditions such as asthma, individuals with weakened immune systems, and individuals living or receiving care in childcare, healthcare, or long-term care settings. Due to underlying medical conditions or reduced immune function, these populations could be at increased risk for adverse health outcomes related to mold exposure. EPH professionals should take these populations into account when assessing mold concerns and providing consultation on remediation and cleanup. In addition, certain facility types and occupancy characteristics might require enhanced controls or compliance with specialized standards to minimize exposure, particularly in healthcare and long-term care settings. 1.3 Escalation and Technical Support In complex situations such as widespread community impacts, elevated exposures, or increased health risks, EPH professionals should consider the need to escalate assistance requests or seek additional technical support. During emergency response, coordination with incident command is critical, and responsibility can shift from local to state agencies or other entities, such as housing authorities. Technical support may be sought from department leadership, program managers, subject matter experts (e.g., toxicologists), industrial hygienists, engineers, partner agencies, or external consultants with specialized expertise.
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
2. Background 2.1 Public Health Significance
the International Building Code, that apply to conditions in residential housing and facilities with other occupancy types.
Addressing indoor moisture and mold remains a persistent challenge and is expected to worsen with increasing extreme weather and flooding. Mold can grow on most moist surfaces, and indoor problems commonly stem from structural housing deficiencies including roof or plumbing leaks, inadequate ventilation, or flooding (Felipo & Charpin, 2022; Park & Cox-Gasner, 2022). Low-income and minority communities may be disproportionately affected by indoor mold due to a greater likelihood of residing in older housing with conditions and deficiencies that can lead to mold growth (Pacheco et al., 2014; Reponen et al., 2013). Indoor mold is both a sanitation and health issue, commonly associated with allergic reactions and respiratory symptoms or disease (American College of Occupational and Environmental Medicine, 2003). 2.2 Regulatory and Legal Framework Regulations for addressing indoor mold vary by setting and jurisdiction, and no federal health-based exposure standards currently exist. Applicable requirements often depend on building type, use, and occupancy. Certain facilities such as schools, restaurants, hospitals, and tourist accommodations might be subject to health, safety, or sanitation codes that require corrective action when mold or unsanitary conditions are present, even if mold is not explicitly mentioned in regulations. For example, food service establishments must maintain sanitary conditions under food codes, and workplaces must remain free from unsafe conditions under occupational health and safety regulations. In residential housing, regulations do not typically apply to owner- occupied homes but might be more common for multi-unit or rental properties. State and local codes, including public health nuisance, sanitation, and housing quality provisions, are usually the most enforceable. For example, landlord–tenant statutes often require landlords to repair leaks and water damage that contribute to mold growth. The International Code Council publishes codes, including
EPH professionals should be familiar with applicable laws, codes, and regulations, and apply professional judgment when interpreting them. Relevant legislation and statutes can be accessed through state and local law databases, online platforms, or in coordination with supervisors, legal counsel, or agency partners. Responsibilities for addressing indoor mold might be shared with or fall under the purview of other government agencies or organizations, depending on facility type, applicable laws, and other circumstances. Collaboration with local code enforcement, building departments, and housing inspection programs is sometimes necessary. While federal agencies do not regulate indoor mold, their guidance might provide a scientific foundation for assessments, complaint responses, recommendations, and enforcement justification. EPH professionals involved in mold assessments might become involved in legal actions if their reports are used as evidence, if they are named as an expert witness, if their work is challenged, or in code enforcement. It is important to maintain thorough documentation, follow recognized guidance and codes, and define the scope and limitations of the assessment.
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
Table 2. Example agencies enforcing codes or regulations that address indoor conditions conducive to mold growth, by setting
SETTING
AGENCY
CODE / REGULATION
FOCUS
Owner-occupied homes
Local building and housing authority
International Building Code (IBC), International Residential Code (IRC), state or local equivalents International Property Maintenance Code (IPMC), local housing code, and rental habitability ordinances Childcare licensing regulations, public health and sanitation codes, IBC, IPMC
Structural conditions conducive to moisture and mold growth
Rental homes and apartments
Local housing authority and code enforcement
Sanitary conditions, and factors impacting habitability
Schools and daycares
State education, childcare, and state or local public health agency
Facility conditions and deficiencies affecting student health
Hotels and tourist accommodations
State or local public health agency Sanitary, public accommodation, and lodging codes, indoor air, water and wastewater provisions State or local public health agency Food and Drug Administration (FDA) Food Code or local/ state equivalent
Sanitation and public health, habitability
Food service establishments
Sanitation, contamination prevention, and facility maintenance Sanitation, moisture control, and prevention of health hazards in the workplace Patient safety, infection control, sanitation, and facility design, condition, and maintenance
Workplaces
Occupational Safety and Health Administration (OSHA) or state OSHA
OSHA General Duty Clause
Healthcare facilities (e.g., hospitals, clinics, nursing homes)
Centers for Medicare and Medicaid Services (CMS), state public health agency, healthcare accreditation organizations
CMS requirements, health codes, licensure regulations, accreditation standards
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
3. Roles and Responsibilities 3.1 Core Activities EPH professionals are uniquely equipped to address indoor mold concerns due to their scientific education and training, risk assessment expertise, and ability to provide technical assistance and public education. Credentialing as a registered environmental health specialist or registered sanitarian (REHS/RS) reinforces these competencies. In response to indoor mold concerns, EPH professionals typically: 1. Assess or support the assessment of homes, buildings, and other indoor environments affected by moisture or mold. 2. Consult on moisture and mold control strategies and cleanup based on assessment results and consistent with public health and industry guidance and relevant laws and codes. 3. Communicate general moisture and mold prevention, and health risk information, especially during disaster response efforts. 3.2 Services Delivery Indoor mold-related services differ across public health agencies and programs and vary based on the type of facility affected, the setting, and if the issue arises during emergency response activities. In many cases, public health agencies address indoor mold concerns primarily through education and information sharing. EPH professionals offer guidance on identifying and addressing mold problems; however, homeowners, building owners, and facility managers are responsible for correcting moisture sources, repairing structural deficiencies, and completing remediation. Public health agencies do not typically offer mold testing services, nor do they certify homes or other facilities as mold-free.
Regulated and public facilities In regulated and public facilities, EPH professionals sometimes assess mold and require corrective actions during inspections or complaint investigations. Programs focused on indoor air quality or healthy homes might give EPH professionals direct responsibilities for inspection, compliance, and enforcement. During emergencies, EPH professional engagement might be more direct and field-based. Integrating indoor mold-related services into disaster preparedness and response plans can improve coordination, clarify authorities, and support access to funding.
Owner-occupied homes and unregulated facilities In owner-occupied homes and unregulated facilities, roles are typically consultative, offering guidance and educational resources. When conducted, home assessments generally focus on visual observations and use of instruments to identify moisture and conditions conducive to mold growth. Structural evaluations are conducted by building inspectors, code officials, or structural engineers, not EPH professionals. Repairs can be costly and complex. Referrals might be made to agencies that provide assistance with housing repairs, particularly those serving low-income, older adult, or disabled populations.
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
Rental and multi-unit housing Rental and multi-unit housing is a common source of mold complaints, raising questions about repair responsibilities and compliance by landlords or tenants. EPH professionals typically provide educational resources to residents and refer them to renter’s rights information, applicable regulations, and enforcement agencies such as a local housing authority. Barriers to addressing indoor mold include remediation costs, unclear responsibility, delayed recognition or reporting, and gaps in regulation or enforcement. In multi-unit housing, remediation can be further complicated by recurring moisture in neighboring units, shared ventilation, and the stack effect, in which temperature differences cause air to rise and fall, moving vertically through a building. Responsibility for cleanup in rental properties generally depends on the cause. Landlords are usually liable for indoor mold resulting from structural issues, such as roof or plumbing leaks, while tenants might be responsible if mold results from their negligence, such as unaddressed water spills.
Table 3. Common EPH Professional Provision of Services to Address Indoor Mold
ACTIVITY
PROVIDED
NOT PROVIDED
• Owner-occupied home assessments • Structural building evaluations • Routine mold testing or sampling
ASSESSMENT
• Assessment guidance for homeowners • Assessment of regulated or public facilities • Regulatory enforcement where applicable
• Direct involvement in remediation or cleanup actions • Clinical advice or diagnosis • Legal advice • Mediate tenant and landlord disputes • Endorse or recommend specific contractors, remediation companies, or products • Certify buildings or homes as mold-free
CONSULTATION • Respond to complaints and inquiries • Suggest remediation and cleanup actions • Refer to external agencies for services and resources
COMMUNICATION • Report on assessment results
• Educate and increase awareness, especially during emergency response • Develop and disseminate informational resources (e.g., fact sheets, websites, social media posts, etc.)
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
4.1 Assess Indoor Moisture and Mold Objectives: • Identify potential sources and extent of indoor moisture and mold growth. • Characterize indoor environmental conditions to inform suggestions for remediation and cleanup actions. Key Activities: • Interview home or facility occupant or representative to gather information on moisture or mold concerns. Use this information to determine if additional investigation is necessary. • Conduct or advise on how to perform indoor assessments to identify moisture sources and determine the extent of mold growth. Document leaks, ventilation deficiencies, and other possible contributing factors. • Perform investigational surveys or moisture mapping when warranted, particularly after flooding or significant water damage. Use tools such as moisture meters, hygrometers, and thermal imaging to detect moisture and measure humidity. Use of infrared thermometers to measure surface temperatures might be a more cost-effective approach than thermal imaging. Summarize findings in a report that identifies and maps affected areas. • Conduct verification surveys to ensure indoor moisture and mold issues have been successfully resolved following remediation and cleanup.
4. Practice-Based Guidance The following guidance supports responses to indoor moisture and mold concerns, organized around three core activities: assess, consult, and communicate. It emphasizes key practices and considerations rather than providing an exhaustive list. The practices described can be applied across a range of settings and engagement, whether delivering direct services, such as conducting assessments, or consulting with homeowners or building managers to identify issues and address remediation, prevention, and cleanup. In addition, these practices might support related activities when moisture and mold concerns arise as part of an emergency response effort. The appendices include links to comprehensive guidance documents and tools to support fieldwork and consultation.
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
Supporting Information: • Scope of EPH professional involvement varies by setting (e.g., residential, public facilities, disaster response), the nature of the request, authorities and regulatory requirements, and the services offered by the public health agency or program. • During emergency response, assessments of indoor moisture and mold might be incorporated into rapid, safety-focused evaluations of disaster-affected buildings. Findings can guide decisions on reoccupancy, remediation, and resource allocation. It is critical to ensure the safety of EPH professionals or responders when conducting indoor assessments. • Mold sampling and analysis are generally not recommended for routine indoor moisture and mold assessments. • Related resources include: • National Institute of Occupational Safety and Health (NIOSH) Dampness and Mold Assessment Tool : Provides a structured checklist and guidance for conducting building assessments. • U.S. Environmental Protection Ageny (U.S. EPA) Moisture Control Guidance for Building Design, Construction, and Maintenance : Offers information relevant to moisture mapping and source identification. Appendix G includes a dampness and mold assessment checklist. • Guidance for Clinicians on the Recognition and Management of Health Effects Related to Mold Exposure and Moisture Indoors (pp. 52–56): Provides information about mold sampling and analysis. • NEHA Environmental Public Health Emergency Preparedness and Response Capability Framework (Function 8: Assure the Integrity and Safety of Buildings): Supports building assessment efforts that include indoor mold. • Appendix A: Comprehensive Guidance and Training • Appendix B: Indoor Mold Assessment Form
• Appendix C: Inspection and Investigation Toolkit Items • Appendix D: Post-Remediation Verification Checklist • Appendix E: Safety Considerations for Indoor Assessments
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
4.2 Consult on Remediation and Cleanup actions Objectives: • Discuss identified environmental conditions that can contribute to indoor moisture and mold. • Provide guidance addressing assessment findings and for the safe cleanup of mold and controlling exposure risks. Key Suggestions: • Repair any moisture sources and structural deficiencies, such as fixing leaks, roofing or plumbing repairs, and addressing other water intrusion issues (U.S. Environmental Protection Agency [U.S. EPA], 2026). • Maintain adequate ventilation and humidity control. Open windows and use fans when practical. Operate air conditioners or dehumidifiers as needed to maintain indoor humidity between 30% and 50%. Ensure that moisture-generating appliances are vented to the outdoors (U.S. EPA, 2026). • Dry water-damaged materials within 24–48 hr. Porous materials such as carpets, upholstery, and fabrics that remain wet for more than 24–48 hr might need to be discarded (Centers for Disease Control and Prevention [CDC], 2024). If the water or moisture source is suspected to contain fecal contamination, hazardous chemicals, or other contaminants, affected materials should be discarded. • Clean hard surfaces using detergent and water. Use of mold- killing chemical products, including a solution of no more than 1 cup of household laundry bleach in 1 gallon of water, is generally unnecessary but can be used when appropriate. Always follow manufacturer instructions and safety precautions when using chemical products (see the FAQs section for more information) (CDC, 2024). • Consider contacting a remediation contractor for extensive mold contamination when affected areas are greater than 10 ft² (U.S. EPA, 2026).
• Avoid breathing in mold or mold spores during cleanup and consider using an N95 respirator, which requires fit-testing in occupational settings. Additional PPE includes long gloves extending to mid-forearm that are appropriate for the cleaning agents used and eye protection such as goggles (U.S. EPA, 2026). • Reassess and monitor indoor areas where remediation occurred to verify that moisture and mold do not reappear (U.S. EPA, 2026). Supporting Information: • Suggestions should be tailored to the setting and population served, with additional precautions for sensitive occupants such as children, older adults, or individuals with respiratory conditions. • More extensive, long-term remediation could be required to fully resolve the issue, ranging from HVAC system upgrades to replacing affected building materials. • Related resources include: • Centers for Disease Control and Prevention (CDC) and U.S. EPA websites for general residential moisture and mold management. • Homeowner’s and Renter’s Guide to Mold Cleanup After Disasters : Provides detailed residential cleanup and PPE guidance. • Federal Emergency Managemeng Agency (FEMA) Dealing With Mold and Mildew in Your Flood Damaged Home : Offers cleanup guidance for flood-damaged homes. • U.S. EPA Mold Remediation in Schools and Commercial Buildings : Includes comprehensive guidance with a remediation checklist (page 27). • U.S. EPA Moisture Control Guidance for Building Design, Construction, and Maintenance : Provides detailed recommendations for long-term moisture management. • World Health Organization (WHO) Guidelines for Indoor Air Quality: Dampness and Mould : Provides key remediation and control considerations focusing on moisture control and ventilation. • Appendix A: Comprehensive Guidance and Training
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
4.3 Communicate Assessment Findings, Guidance, and General Health Risk Information Objectives: • Report assessment findings with remediation and cleanup suggestions. • Share general information about exposure and health risks. • Increase public awareness of moisture control and mold cleanup actions, particularly during and after disasters, flooding, or other extreme weather events. Key Activities: • Engage with homeowners, building managers, and community members to share assessment findings, provide guidance, and answer questions. • Distribute educational materials, including but not limited to, fact sheets, brochures, or digital resources that explain remediation and safe cleanup of indoor moisture and mold, as well as potential exposure risks and health impacts. • Coordinate communication efforts during emergency response operations to ensure consistent messaging about mold prevention and health protection.
Supporting Information: • Strong collaboration with local, state, and federal emergency preparedness partners is essential to ensure EPH is fully integrated into planning and response activities, including efforts to address indoor moisture and mold. • Community-level communications should use a variety of media and channels, including digital platforms, broadcast media, printed materials, and direct interpersonal outreach, to effectively reach impacted individuals and populations. • Related resources include: • U.S. EPA Mold Remediation in Schools and Commercial Buildings : Provides guidance for communicating with building occupants in Appendix C (p. 45). • CDC Mold Resources and Publications webpage : Offers downloadable fact sheets and outreach materials. • FEMA Dealing With Mold and Mildew in Your Flood Damaged Home and the Homeowner’s and Renter’s Guide to Mold Cleanup After Disasters : Essential resources and information for developing disaster-related communication materials. • Appendix F: Example Email Response to Requests or Inquiries • Appendix G: Key Messages and Discussion Points • Appendix H: Example Emergency Response Communications Plan • Appendix I: Example Social Media Messages
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
5. Frequently Asked Questions (FAQs) What is mold?
Mold is a type of fungus that is part of the natural environment and grows both outdoors and indoors. Molds reproduce by spores that are not visible without magnification and are present in outdoor and indoor air. While all molds are fungi, not all fungi are molds. Other fungi include single-celled yeasts or macroscopic forms, such as mushrooms, and do not typically exhibit the same indoor surface growth or spore dispersal. Mold growth occurs when spores land on surfaces with sufficient moisture and nutrients. Mold can develop on a wide range of materials, such as paper, wood, drywall, insulation, carpet, dust, and fabrics. Indoor mold growth is commonly associated with water intrusion, high humidity, or inadequate moisture control. Does mold impact health? Mold in damp indoor environments can contribute to health problems such as allergies, transient mucous membrane irritation, and in rare instances, infections among people with compromised immune systems. Damp indoor spaces might also contain other organisms and substances that contribute to health problems, such as dust mites, bacteria, and cockroaches. It is often difficult to attribute health effects associated with damp indoor environments specifically to mold alone. The primary health effects of concern associated with indoor mold include allergic conditions such as allergic rhinitis (hay fever) and asthma. Irritation of the eyes, nose, and throat, as well as coughing, sneezing, and a runny nose, are frequently reported as well. Other nonspecific symptoms can include headache and dizziness. Typically, these symptoms improve when the individual leaves the damp environment. Some mold species produce natural compounds called mycotoxins that can be poisonous to humans if ingested. Certain mycotoxins, such as aflatoxins, trichothecenes, and ochratoxins, are produced by molds that grow on crops such as grains, nuts, and coffee, causing food contamination and potential outbreaks of illness.
There are many misconceptions about so-called "toxic mold" in indoor spaces causing illness. Scientific evidence does not support the idea that inhaled mycotoxins actually cause measurable human health effects. Mycotoxins are large, complex molecules that are not volatile, and their concentrations in air are very low. In the 1990s, the mold Stachybotrys chartarum gained notoriety as a suspected cause of pulmonary hemorrhage (i.e., bleeding in the lungs) among infants, and other severe health effects based on preliminary epidemiologic studies. As such, the mold earned the nickname, "toxic black mold." Subsequent studies do not support a conclusive link between Stachybotrys and human illness. Mold can also produce volatile organic compounds (VOCs) that cause a musty odor. At high doses of exposure, VOCs are associated with eye, nose, and throat discomfort and subjective headache and dizziness. The health effects of VOCs are transient, and symptoms usually resolve once an individual is no longer exposed or leaves the immediate area. When individuals report persistent nonspecific symptoms such as neurologic or cognitive effects (e.g., brain fog) they should not be attributed to mold exposure. Further medical workup for other causes of these symptoms could be warranted. What are some signs that my home might have mold? Common signs of mold include visible moisture and mold, musty or earthy odors, water stains, recent flooding, or known moisture issues such as leaks or condensation. Detecting hidden mold requires a more thorough assessment, including help from a trained professional.
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
Do you recommend testing my home for mold? Routine mold testing is usually not needed. Any indoor mold should be cleaned up as soon as it is found, and there are no established standards for safe levels of mold exposure. Mold testing can be complex, time-consuming, expensive, and often does not provide useful information about health risks. If mold testing is conducted, the work should be done by qualified professionals with experience in mold sampling, test design, and result interpretation. Samples should be analyzed using methods recommended by recognized professional organizations, such as the American Industrial Hygiene Association (AIHA), the American Conference of Governmental Industrial Hygienists (ACGIH), or similar groups (U.S. EPA, 2026). Is it possible to be tested for mold exposure? Patients are often faced with misleading and confusing claims regarding unvalidated diagnostic tests. There is no diagnostic test to support inhaled mycotoxins from indoor mold as a cause of systemic toxicity. Fungal immunoassay tests (i.e., testing for IgG and IgE) might be useful for assessing hypersensitivity pneumonitis, allergies, and other immunological conditions. They should typically be ordered and interpreted by physicians with specialized training in allergies and immunology. These tests do not measure levels of exposure to indoor mold, and positive results do not mean that there is current exposure or that mold is the cause of illness or symptoms. Individuals who have concerns about the health effects of indoor mold exposure should speak with their healthcare provider, who can help determine what approach is appropriate for their individual situation. In the meantime, attention is best directed toward identifying and cleaning affected areas and correcting the underlying moisture sources in the home.
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
What are the important steps for getting rid of and preventing mold?
Should I use bleach to clean up mold? Routine use of bleach or other mold-killing chemicals is not recommended. Completely sterilizing an area is usually unnecessary and not possible. Some mold spores can remain after cleanup, but they will not grow if moisture problems are fixed. It is also important to physically remove mold rather than only killing it, because dead mold can still cause allergic reactions (U.S. EPA, 2025). In some cases, using bleach during mold cleanup may be considered, especially when building occupants have weakened immune systems or mold allergies. Bleach can reduce mold spores and mycotoxin levels and can break down allergenic proteins, which might help reduce allergic reactions (Chen & Eggleston, 2001; Wilson et al., 2004). Bleach works best on nonporous surfaces such as tile or sealed countertops. It is less effective on porous materials like drywall, wood, and fabric. If bleach is used, mix no more than 1 cup of household bleach with 1 gallon of water. Make sure the area is well ventilated and never mix bleach with ammonia or other cleaning products. Wear protective gear such as rubber gloves, boots, and goggles (CDC, 2024). Always follow the manufacturer’s instructions and safety guidelines when using bleach or other mold-killing chemicals.
The most important steps for getting rid of and preventing mold are to eliminate moisture sources and safely clean up visible mold. Repair leaks and structural problems promptly, maintain good ventilation, and keep indoor humidity between 30% and 50%. Dry water-damaged materials within 24–48 hr and discard porous items that stay wet. If the water or moisture source is suspected to contain fecal contamination, hazardous chemicals, or other contaminants, affected materials should be discarded. Clean hard surfaces with detergent and water, using disinfectants as needed, and wear appropriate protective gear such as an N95 respirator, gloves, and goggles. For mold-contaminated areas larger than 10 ft², U.S. EPA recommends hiring a qualified remediation professional.
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
Is a landlord responsible for mold remediation? In rental properties, responsibility for mold cleanup might depend on its cause. If mold results from a structural issue, like a roof or plumbing leak, the landlord is typically responsible. If it stems from tenant negligence, such as an unaddressed water spill, the tenant could be liable. Tenants can document the situation, formally notify the landlord, review local laws, and consider consulting with a legal professional. They can also seek help from local government agencies, including housing authorities or programs that regulate rental properties and enforce health and safety regulations requiring landlords to remediate the issue.
What if a tenant refuses to remediate mold? Determining whether a tenant’s actions contributed to conditions that led to mold growth can be challenging. If tenant negligence is established, a landlord can pursue remedies such as requiring the tenant to correct the issue or cover cleanup costs, withholding a security deposit, or initiating eviction, as allowed by law. Landlords can document conditions, provide formal notice to the tenant, review applicable laws, and consult a legal professional. They can also seek assistance from local agencies that enforce health and safety requirements. Whenever possible, landlords and tenants should work together to develop a remediation plan. Whom should I contact for help with conducting mold cleanup and remediation actions? Consider seeking help from qualified professionals experienced in mold inspection or remediation and credentialed, certified, or affiliated with organizations such as the NEHA; AIHA; the Institute of Inspection, Cleaning, and Restoration Certification (IICRC), or the American Council for Accredited Certification (ACAC) (Hurricane Sandy Rebuilding Task Force, 2015). There is no federal certification program for mold assessors. A small number of states, including Texas, New York, Florida, and Louisiana, require formal licensing or certification for mold assessors and often mandate specific training, examinations, written protocols, post-remediation verification, and separation between assessment and remediation roles. Most states, however, do not regulate mold assessors directly, allowing individuals to practice without a state- issued credential. In those states, professional credibility is typically established through experience, industry certifications, and adherence to accepted guidance.
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
6. References American College of Occupational and Environmental Medicine. (2003). Adverse human health effects associated with molds in the indoor environment. Journal of Occupational and Environmental Medicine, 45 (5), 470–478. https://doi.org/10.1097/00043764-200305000- 00006 Bare, G., Kim, T.N., Hedberg, C.W., Dutra, N., Walker, C., & Dyjack, D. (2025). Pillars of governmental environmental public health: A guide to scalable environmental public health programs . National Environmental Health Association. https://pubs.neha.org/2025-pillars-of-eh/
Pacheco, C.M., Ciaccio, C.E., Nazir, N., Daley, C.M., DiDonna, A., Choi, W.S., Barnes, C.S., & Rosenwasser, L.J. (2014). Homes of low-income minority families with asthmatic children have increased condition issues. Allergy and Asthma Proceedings, 35 (6), 467–474. https://doi. org/10.2500/aap.2014.35.3792 Park, J., & Cox-Ganser, J.M. (2022). NIOSH Dampness and Mold Assessment Tool (DMAT): Documentation and data analysis of dampness and mold-related damage in buildings and its application. Buildings, 12 (8), Article 1075. https://doi.org/10.3390/ buildings12081075 Reponen, T., Levin, L., Zheng, S., Vesper, S., Ryan, P., Grinshpun, S.A., & LeMasters, G. (2013). Family and home characteristics correlate with mold in homes. Environmental Research, 124 , 67–70. https://doi. org/10.1016/j.envres.2013.04.003 U.S. Environmental Protection Agency. (2025). Should I use bleach to clean up mold? https://www.epa.gov/mold/should-i-use-bleach-clean- mold U.S. Environmental Protection Agency. (2026). A brief guide to mold, moisture and your home . https://www.epa.gov/mold/brief-guide-mold- moisture-and-your-home Wilson, S.C., Brasel, T.L., Carriker, C.G., Fortenberry, G.D., Fogle, M.R., Martin, J.M., Wu, C., Andriychuk, L.A., Karunasena, E., & Straus, D.C. (2004). An investigation into techniques for cleaning mold-contaminated home contents. Journal of Occupational and Environmental Hygiene, 1 (7), 442–447. https://doi. org/10.1080/15459620490462823
Centers for Disease Control and Prevention. (2024). Mold . https://www. cdc.gov/mold-health/about/index.html
Chen, P., & Eggleston, P.A. (2001). Allergenic proteins are fragmented in low concentrations of sodium hypochlorite. Clinical and Experimental Allergy, 31 (7), 1086–1093. https://doi.org/10.1046/j.1365- 2222.2001.01127.x Felipo, R., & Charpin, D. (2022). Structural home defects are the leading cause of mold in buildings: The housing and health service experience. International Journal of Environmental Research and Public Health, 19 (24), Article 16692. https://doi.org/10.3390/ijerph192416692 Hurricane Sandy Rebuilding Task Force–Indoor Environmental Pollutants Work Group. (2015). Homeowner’s and renter’s guide to mold cleanup after disasters . U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, U.S. Environmental Protection Agency, Federal Emergency Management Agency, U.S. Department of Housing and Urban Development, and National Institutes of Health. https://www.cdc.gov/mold-health/media/ Homeowners_and_Renters_Guide.pdf
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
Appendix A. Comprehensive Guidance and Training Publications
8. Homeowner’s and Renter’s Guide to Mold Cleanup After Disasters . (2015). https://www.cdc.gov/mold-health/media/Homeowners_and_ Renters_Guide.pdf
1. American Industrial Hygiene Association. (2020). Facts About Mold: A Consumer Focus . https://www.aiha.org/education/fact-sheets/ facts-about-mold-a-consumer-focus 2. American Industrial Hygiene Association. (2020). Recognition, Evaluation, and Control of Indoor Mold (the Green Book). Available for purchase at https://www.aiha.org/public-resources/ healthierworkplaces/healthier-community-resources/disaster- response-resource-center/mold-resource-center 3. Environmental Law Institute. (2025). Database of State Indoor Air Quality Laws. Database Excerpt: Mold Laws. https://www.eli.org/ sites/default/files/files-pdf/2025%20Mold.pdf 4. U.S. Environmental Protection Agency (2008). Mold Remediation in Schools and Commercial Buildings . https://www.epa.gov/sites/ default/files/2014-08/documents/moldremediation.pdf 5. Federal Emergency Management Agency. (n.d.). Dealing With Mold and Mildew in Your Flood Damaged Home . https://www.fema.gov/ pdf/rebuild/recover/fema_mold_brochure_english.pdf 6. Guidance for Clinicians on the Recognition and Management of Health Effects Related to Mold Exposure and Moisture Indoors. (2004). https://health.uconn.edu/occupational-environmental/wp- content/uploads/sites/25/2015/12/mold_guide.pdf 7. Health Canada. (2016). Residential Indoor Air Quality Guidelines: Moulds . https://www.canada.ca/content/dam/canada/ health- canada/migration/healthy-canadians/publications/healthy-living- vie-saine/mould-moisissure/ alt/mould-moisissures-eng.pdf
9. Institute of Medicine. (2004). Damp Indoor Spaces and Health . https://doi.org/10.17226/11011
10. National Institute for Occupational Safety and Health. (2018). Dampness and Mold Assessment Tool: General Buildings, Form & Instructions . https://www.cdc.gov/niosh/docs/2019-115/ pdfs/2019-115.pdf 11. Occupational Safety and Health Administration. (2005). Fungi Hazards and Flood Cleanup . https://www.osha.gov/sites/default/ files/publications/Bulletin3.pdf 12. Occupational Safety and Health Administration. (2006). Preventing Mold-Related Problems in the Indoor Workplace. A Guide for Building Owners, Managers and Occupants . https://www.osha.gov/ sites/default/files/publications/preventing_mold.pdf 13. World Health Organization, Europe. (2009). WHO Guidelines for Indoor Air Quality: Dampness and Mould . https://iris.who.int/server/ api/core/bitstreams/9261a374-7d3b-4825-a61e-0c09dea2af87/ content
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
Websites 1. American Industrial Hygiene Association: Mold Resource Center. https://www.aiha.org/public-resources/healthierworkplaces/ healthier-community-resources/disaster-response-resource-center/ mold-resource-center
Training 1. U.S. Environmental Protection Agency: Mold Course. https://www. epa.gov/mold/mold-course-introduction 2. U.S. Department of Housing and Urban Development: Public Housing Authority (PHA) Training: Detecting and Addressing Hazards from Mold. https://www.hudexchange.info/trainings/pha- training-detecting-and-addressing-hazards-from-mold/ 3. International Association of Certified Home Inspectors: How to Perform Mold Inspections Course. https://www.nachi.org/ moldcourse.htm 4. National Association of Mold Professionals: Mold Inspector Certification Training. https://www.360training.com/course/mold- inspector-certification 5. National Collaborating Centre for Environmental Health: Mould Investigation: An Online Course for Public Health Professionals. https://ncceh.ca/mould-investigation-online-course-public-health- professionals
2. Centers for Disease Control and Prevention: Mold. https://www.cdc. gov/mold-health/about/index.html
3. U.S. Environmental Protection Agency: A Brief Guide to Mold, Moisture and Your Home. https://www.epa.gov/mold/brief-guide- mold-moisture-and-your-home
4. National Environmental Health Association: Mold Remediation Resources. https://www.neha.org/mold-remediation-flood
5. National Institute for Occupational Safety and Health: Responding to Disasters and Extreme Weather. https://www.cdc.gov/niosh/emres/ response/index.html?CDC_AA_refVal=https%3A%2F%2Fwww. cdc.gov%2Fniosh%2Ftopics%2Femres%2Fcleaning-flood-hvac. html
6. Occupational Safety and Health Administration: Mold. https://www. osha.gov/mold
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Responding to Indoor Mold Concerns: A Resource for Environmental Public Health Professionals
Appendix B: Indoor Mold Assessment Form Resident & Home Information
Resident Name: Home Address:
Contact Information: Assessment Date:
Interview Questions
QUESTION
RESPONSE COMMENTS
YES □ NO □ YES □ NO □ YES □ NO □ YES □ NO □ YES □ NO □ YES □ NO □ YES □ NO □ YES □ NO □ YES □ NO □
Is mold visible on ceilings, walls, floors, or other areas?
Are occupants reporting symptoms possibly related to mold exposure (e.g., coughing, sneezing, headaches)?
Is there visible water damage or staining?
Is a musty or earthy odor present?
Was the home previously affected by flooding?
Is a humidifier or air conditioner available?
Are there any known roof leaks?
Are there any known plumbing leaks?
Does condensation accumulate on windows?
NOTES
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