Air Monitoring: Metropolis Towers
Through November 6, 2017
Project-to-date concentrations
remain within
safety limit
As indicated at left, airborne concentrations of hexavalent chromium at Metropolis Towers during the cleanup are in compliance with the site-specific airborne concentration limit established by the NJDEP in consultation with the independent technical consultant. Work was conducted from March 18 to Aug. 14, 2013, and Oct. 2, 2013 to Aug. 12, 2014. Work resumed Sept. 8, 2017.
Detailed Reports
Monitor Locations

Protection of human health is a priority during PPG Industries’ clean-up operations at all of its chromium sites, including Metropolis Towers. To protect the community, PPG is using proven containment and control measures that have been approved by the New Jersey Department of Environmental Protection following a review by the independent technical consultant.

Among these protective measures is a dust-suppression plan designed to prevent excavated materials, including hexavalent chromium, from becoming airborne. Elements of the plan include water misting of work areas, spraying surfaces with dust-suppression materials and restricting truck traffic to paved areas. PPG has installed air monitoring stations at ground level and at an elevation of 15 feet at the perimeter of work zones to maintain safe conditions during cleanup activities. Some of the monitors are only used while work is taking place but others operate 24 hours a day, seven days a week. Data from these monitors are posted to this website.


Chromium samples are collected and results are compared to a limit established by NJDEP specifically for the Metropolis Towers Site. The limit is 49 nanograms per cubic meter of air, which is considered to be protective of human health based on U.S. Environmental Protection Agency assumptions for cancer risk. To meet the limit, average airborne concentrations of hexavalent chromium must be at or below 49 nanograms per cubic meter of air for the duration of the remediation. Monitoring for specific compounds such as chromium requires samples be collected and sent to a lab for analysis.


Dust, meanwhile, can be measured in real time while work is taking place, allowing workers to take immediate action designed to protect community health if needed. As a result, PPG continuously measures dust as a surrogate for hexavalent chrome. Certain monitors take measurements 24 hours a day, seven days a week. The NJDEP-approved air monitoring plan established a limit on total dust of 339 micrograms per cubic meter measured on one and five-minute averages. This limit is also known as the action level. Full-time air monitoring technicians located on site while work is being conducted review these readings to control site operations and implement additional dust-suppression measures as needed to protect the community.

* Monitor No. 36 was proposed but ultimately not needed when excavation work areas were reconfigured.