Indoor Air Quality Alert: Sri Lanka Flooding

What is the location of the flooding?

As of December 1, 2025, Sri Lanka is battling one of its worst flood disasters in decades after Cyclone Ditwah made landfall on November 28. The storm unleashed record-breaking rainfall, widespread river overflows, and deadly landslides across all 25 districts.

The hardest-hit areas include Gampaha, Colombo, Puttalam, Mannar, Trincomalee, and Batticaloa, while severe landslides devastated Kandy, Badulla, and Matale in the central highlands. Vast regions remain underwater, with flooding along the Kelani River continuing to threaten Colombo and surrounding low-lying communities.

Nearly one million people have been affected, and the system’s impact has been worsened by repeated infrastructure failures, blocked roads, and a fragile communication network (1).

Which cities or areas are affected by the flooding?

The areas impacted by Cyclone Ditwah and the resulting Sri Lanka floods include:

• Kandy, Badulla, and Matale (central landslide zone)
• Colombo and surrounding suburbs
• Gampaha (Colombo outskirts)
  
• Jaffna and northern districts with major communication outages
• Kelani River valley communities
• Puttalam and Mannar districts
• Southern and western provinces experiencing severe river overflows
• Trincomalee and Batticaloa (east)

These regions continue to experience heavy rainfall, landslides, submerged homes, and rising river levels. More than 200 roads, multiple bridges, and key railway corridors remain impassable, hampering rescue and relief operations nationwide (2).

What is the current containment status of the flooding?

Containment remains extremely difficult as rescue teams struggle to access isolated communities. According to national and UN agencies, more than 24,000 army, navy, police, and air force personnel are deployed, with helicopters airlifting stranded patients and families cut off by landslides and flooding.

Over 15,000–20,000 homes have been destroyed, with entire towns submerged. Floodwaters breached the Mavil Aru reservoir, forcing thousands to evacuate, while disruptions to electricity, communications, and clean water continue across at least one-third of the country.

Hospitals in several districts have been flooded or are receiving only limited supplies, prompting WHO warnings of rising risks of water-borne and vector-borne diseases (3).

Are there any evacuation orders or alerts in place?

A state of emergency has been declared nationwide as evacuation orders expand across flood-prone districts. More than 180,000–200,000 people have taken shelter in over 1,000 government-run centers, with numbers continuing to rise.

Authorities warn communities along the Kelani River, central landslide zones, and eastern districts to move to higher ground immediately. The government has appealed for international assistance, with India, Pakistan, and UN agencies already supporting response operations (4).

How can I protect myself from mold after flooding?

It’s important to take steps to prevent mold after a flood.

• Before entering a flooded area, make sure it is safe and free from electrical hazards or structural damage.
• Use protective gear: wear gloves, goggles, and a KN95/FFP2 mask to minimize exposure to mold spores.
• If there is still standing water, remove it as quickly as possible. Use pumps, wet-dry vacuums, or buckets to extract the water.
• Open windows and doors to facilitate air circulation and use fans, dehumidifiers, and HVAC systems to help dry the space. This step is crucial within the first 24-48 hours after flooding to prevent mold growth.
• Remove and discard any items that have been severely damaged by floodwater and cannot be thoroughly cleaned and dried. This includes carpets, upholstered furniture, mattresses, and any other porous materials.
• Thoroughly clean all hard surfaces with a detergent or cleaner suitable for mold remediation. Use a solution of 1.5 cups of bleach mixed with one gallon of water to disinfect nonporous surfaces. Never mix bleach with ammonia or other cleaning products, as the fumes are toxic.
• Maintain an indoor relative humidity (RH) of 35-50%. High humidity promotes mold growth, so consider using dehumidifiers in damp areas.
• Run a high-performance air purifier for mold, both during and after the mold removal work.
• If the flooding and mold damage are extensive, consider contacting professionals specializing in mold remediation to ensure proper cleanup and restoration.

Remember, mold can pose health risks, so it's important to take these steps promptly and thoroughly. If you experience persistent mold-related health issues or have concerns about extensive mold growth, consult with a medical professional or a mold remediation specialist.