The 9-11 terrorist attack has left a legacy of multiple myeloma among the firefighters exposed to chemicals at the collapsed World Trade Centre, US researchers say.

A case series of 16 of the 9-11 firefighters diagnosed with multiple myeloma has found that exposure to the World Trade Centre (WTC) disaster site is associated with myeloma precursor disease (monoclonal gammopathy of undetermined significance and light-chain MGUS) and may be a risk factor for the development of multiple myeloma at an earlier age.

Published in JAMA Oncology, the study found the median time to MM diagnosis was 12 years after the attack and the median age at diagnosis was 57 years  – compared to 69 years for the general population.

The firefighters had an unusual pattern of disease, with a high proportion of the cases (50%) having light-chain myeloma, double the usual proportion in the population. In addition,  plasma cells were CD20 positive in 71% of cases, compared to 13% to 22% of patients with multiple myeloma diagnosed in the general population.

Exposure to the WTC site was found to be statistically significantly associated with light-chain MGUS and overall MGUS.

The researchers said the firefighters were exposed to aerosolised dust and toxic fumes from burning jet fuel and building materials at the WTC site during the 10 months of the rescue, recovery, and cleanup effort.

Potential carcinogens included pulverised cement, glass fibres, asbestos, lead, PAHs, PCBs, and polychlorinated furans and dioxins produced as combustion byproducts from the collapsed and burning buildings.

As well as having a direct carcinogenic effect, the dust and toxins could trigger chronic inflammation resulting in upper and lower respiratory diseases and autoimmune diseases, and inlammation-induced oncogenesis.

While not showing a conclusive evidence of a link between WTC and cancer the study strongly suggested that exposure may be a risk factor for the development of multiple myeloma and its precursor disease, according to a commentary by Dr Otis Brawley, of the Department of Hematology and Oncology, Emory University, Atlanta.