Black Particulate Event - Early July 2026

Environmental vs Exposure

Environmental data are measurements of contaminants in the environment such as air, water and soil, at a specific location and time. These data do not directly represent what people actually inhaled or absorbed because they do not account for factors such as how long people are exposed, where they spend time, indoor/outdoor differences or individual physiological differences. These factors are required to determine the amount of a substance that enters or comes into contact with a person, informing individual health risk.

Hamilton Public Health comprehensive assessment findings

Summary

• Hamilton Public Health’s assessment included a review of information and observations reported by affected residents, air quality data from the Hamilton Air Monitoring Network, weather data, acute health effects from hospital emergency departments, the MECP report, as well as consultations with toxicology experts and Public Health Ontario. 
• Hamilton Public Health’s review of Acute Care Enhanced Surveillance (ACES) data, which is local emergency department data, determined there had been no increase in visits to the emergency department for more severe symptoms. 
• Hamilton Public Health’s review of the daily 24-hour average concentrations for PM₁₀ and PM_2.5 identified exceedances of the 50 µg/m³ Ambient Air Quality Criteria (AAQC) for PM10 at various monitoring locations and dates between July 1 to 14, 2026.
• The emissions are found to be primarily graphitic carbonaceous particles intermixed with mineral dust components.
• The observed particle characteristics are consistent with particulate matter commonly found in urban and industrial environments.
• The MECP report noted that for longer-term exposure to the soot/black particulate, the main concern would be potential carcinogen-risk. While the material could be inhaled if it becomes airborne, such as sweeping or disturbing, MECP expects ongoing exposure to be limited and do not anticipate significant long-term exposure risks such as dermal, inhalation and/or ingestion.   

Hamilton Air Monitoring Network Data

Measured airborne particulate matter (PM₁₀ µg/m³ and PM_2.5 µg/m³) 14-day average concentrations from July 1 to 14, 2026 at the Beach, Parkdale, St. Christopher’s Park, Gage, and Wentworth air monitoring stations were reviewed by the MECP. Findings indicate that for PM₁₀, relative to the corresponding period in 2025 (27 to 35 µg/m³), all stations except Wentworth recorded higher PM₁₀ average concentrations in 2026 (26 to 41 µg/m³); however, concentrations remained somewhat comparable between the two years. The MECP’s findings for PM_2.5 average concentrations during the period from July 1 to 14 in 2025 (14 to 18 µg/m³) and 2026 (12 to 18 µg/m³) were comparable. 

PM₁₀ values show exceedances of the 50 µg/m³ AAQC on July 1, 2026, recorded at the Beach (67 µg/m³), Parkdale (69 µg/m³), St. Christopher’s Park (64 µg/m³), Gage (71 µg/m³) and Wentworth (50 µg/m³) monitoring stations with exceedance again recorded the following day July 2, 2026, at the Beach (56 µg/m³), Parkdale (57 µg/m³), St. Christopher’s Park (59 µg/m³), and Gage (66 µg/m³) stations. Additionally, there was an exceedance of the AAQC for PM₁₀ on July 13, 2026, at the Beach (78 µg/m³) station and on July 14, 2026, at the Beach (109 µg/m³), Parkdale (55 µg/m³) and Gage (66 µg/m³) stations. These observations support that a notable occurrence took place during the beginning of July 2026, influencing PM10 concentration recorded in the lower city.

With respect to PM_2.5 concentrations, there was an exceedance of the 24-hour 27 µg/m³ AAQC on July 12, 2026, at the St. Christopher’s Park (29 µg/m³) station.

The 24-hour (AAQC) used as a reference level measuring maximum desirable average concentrations of specific pollutants in open outdoor air to prevent negative health or environmental impacts is 50 µg/m³ for PM₁₀ and 27 µg/m³ for PM_2.5 in Ontario.

Air Quality Health Index (AQHI) Data

• The AQHI Hamilton Downtown Monitor for July 2 to July 14 recorded values in the range from 1 (low risk) to 4 (medium risk). Data for July 1, 2026, was not available for the Downtown monitoring station.
• The AQHI Hamilton Mountain monitoring station for July 1 to July 14 recorded values in the range from 1 (low risk) to 4 (medium risk). 

Weather Data

• Between July 1 to 12, 2026, there were four heat warning days on July 1, 2, 3, and 4.
• Hamilton Airport Station shows five days of precipitation on July 1, 3, 4, 6, and 9.
• Royal Botanical Gardens Station shows five days of precipitation on July 1, 2, 3, 4 and 9.  

Environmental sampling findings

• There were several rainfall events, weathering, dispersion and cleanup after the July 5, 2026 onset of black particulate complaints, and the available data suggests that long-term inhalation risks are not expected to be significant.
• Laboratory analysis indicates that samples consisted primarily of carbonaceous material (soot-like, coal/coke-like).   
• Soot-like particles likely result from combustion and coal/coke-like particles likely result from industrial sources.  
• The repeated occurrence of silica, aluminosilicates, carbonates and iron oxides within the local environment indicates that the carbonaceous particles have become mixed with common environmental or industrial mineral dusts. These minerals are consistent with soil-derived particulates, construction materials, road dust and other ubiquitous environmental particulate matter. These materials suggest atmospheric transport, environmental deposition, or mixing with background dust. 
• The polyaromatic hydrocarbon (PAH) results indicate that most sampling locations exhibited low to moderate concentrations consistent with urban, transportation, and industrial deposition. In contrast, two samples collected from Birla Carbon contained substantially elevated PAH concentrations, carbon-rich particulate material. 
• The PAH profiles for all other samples are consistent with combustion-related sources; however, given the proximity of a major highway and steel manufacturing facility, the results likely reflect the cumulative influence of multiple industrial and transportation-related sources rather than a single contributor. 
• Interpretation is limited by the other potential PAH sources, including coal and coke materials, historical coal-handling activities, soot deposits, and vehicular emissions, all of which can exhibit PAH distributions similar to those associated with carbon black, a manufactured material used in a variety of products including tires, paints, inks, plastics, food products, cosmetics, pharmaceuticals, and natural health products. Because PAHs are produced by a wide range of combustion and thermal processes, they are generally considered source-indicative (i.e., points towards general type/category) of rather than source-specific (i.e., points towards exact origin). 
• MECP reviewed local continuous air monitoring data collected from the Parkdale and Gage stations reported via the Hamilton Air Monitoring Network (HAMN) from July 1 to 14, 2026. Wind rose data indicates winds were predominantly from the northeast and southwest. 
• Given that the complainant locations are generally situated southwest of the Parkdale station, the spatial patterns may be indicative of a potential source located near or northeast of the station during periods of northeasterly winds. 
• MECP has identified Birla Carbon located on Parkdale Avenue North as being a primary source of the material.