Review of Environmental Exposures after the World Trade Center Disaster and its Effects on Health and Disease

The World Trade Center (WTC) disaster created an environmental exposure to aerosolized dust and gases that contained various genotoxic and carcinogenic chemicals. Various analyses of the WTC particulate matter have shown that it contained high concentrations of heavy metals, ionics and asbestos derived from pulverized building materials. WTC dust collected from the site also contained organic carcinogens including Polycyclic Aromatic Hydrocarbons (PAHs), polychlorinated biphenyls, polychlorinated dibenzodioxins and other hydrocarbons. These chemicals can lead to DNA damage, contributing to an increased risk of prostate cancer, thyroid cancer, myeloma and other cancers in first responders. Exposure to the dust cloud also potentially led to systemic inflammatory responses that contributed to lung and heart diseases seen in the exposed population. The effects of WTC exposure continue to be felt in first responder and other exposed populations, even many years after the exposure, underscoring the impact of the environment on human health.

On September 11, 2001, a terrorist attack initiated the collapse of the World Trade Center (WTC) Twin Towers and resulted in 2,977 fatalities. Over two decades later, people are still affected by the consequences of the collapse of the towers due to the exposure to unprecedented amounts of particulate matter that covered large parts of New York City. The health of many responders and New York City residents were affected due to the exposure [1-3]. Days after the collapse, scientists gathered samples of the WTC dust for analysis. Chemical analysis and research of the WTC dust samples is important because each chemical affects health differently. This article aims to review the scientific analyses of the major chemicals found in World Trade Center dust on three streets close to the WTC (Cortlandt, Cherry, and Market Streets) [1,4-7] (Table 1).

Using various analytical and microscopic techniques, scientists determined the chemical composition of the WTC dust constituents and categorized its composition into inorganic and organic categories. When investigating the inorganic matter making up the WTC dust, researchers discovered that the inorganic matter of the samples consisted of metals, radionuclides (atoms with unstable nuclei), ionic species, asbestos, and inorganic species [1,4-6].

Metals

Metals, particularly toxic and heavy metals, were identified and categorized using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis and Scanning Electron Microscopy (SEM) analysis [1,4-6]. The results of the ICP-MS experiments showed high levels of Chromium, Aluminum, Manganese, and Barium, which are often found in construction materials. Chromium compounds are considered carcinogenic and increase the risk of developing lung, nasal, and sinus cancer [8]. Aluminum toxicity causes neurological and musculoskeletal complications such as osteoporosis, bone fractures, dementia, seizures, tremors, dysarthria, impaired coordination, and motor weakness [9]. The results also showed high concentrations of lead as it was present in metallic paints used during the construction of the World Trade Center building. Exposure to lead dust can increase the risk of hypertension and heart diseases, cause headaches, difficulty concentrating, memory loss, reduced motor speed, and kidney dysfunction. Additionally, the SEM analyses displayed elevated levels of construction materials iron and calcium, as well as silicon and sulfur. The analyses also uncovered trace elements from fiberglass and other inorganic fibers.

Radionuclides

The gamma spectrum, or the gamma radiation emitted by radioactive material within the sample, was detected and measured using an EG&G/Ortec high-purity Ge detector (50% relative efficiency) gamma counter. Subsequently, the samples’ radioactivity emissions were measured using liquid scintillation analysis. Using this technique, researchers found only background levels, or the same amount of radiation present in the natural environment, of alpha radionuclide activity, in all the dust samples. Although beta radiation activity was found to be slightly elevated in the samples, it was no more than twice the background level of beta activity in nature. In terms of gamma activity, gamma activity levels stayed below 1 Bq/g (Becquerel per gram) for all elements except for naturally occurring potassium-40.

Ionic species

Scientists performed Ion chromatography to separate and analyze ionic species in the collected dust samples. The anions and cations detected to be elevated on Cortlandt, Cherry, and Market streets collections were fluoride, chloride, nitrate, sulfate, calcium, sodium, and potassium. Researchers speculated that the high sulfate levels had formed in the fires and that the high calcium values were due to the pulverization of building materials. High exposure to potassium fluoride can lead to fluorosis and cause pain, disability, and mottling of the teeth. High exposure to chloride can cause pulmonary edema and severe shortness of breath [10]. Similarly, Methemoglobinemia is a critical health effect from exposure to nitrates and nitrites.

Asbestos and inorganic species

Morphologic analyses were used to detect the presence and amount of asbestos– fibrous crystals linked to serious health risks– and other inorganic species. Within the dust samples collected in Cortlandt, Cherry, and Market Streets, chrysotile asbestos (a type of asbestos) comprised 0.8%, 0.8%, and 3% of the three samples respectively. Additionally, all three samples were reported to be 40% glass fiber [5].

In contrast, after performing scientific analyses on the organic matter making up the WTC dust, researchers concluded that the organic composition of the dust contained Polycyclic Aromatic Hydrocarbons (PAHs), polychlorinated biphenyls, polychlorinated dibenzodioxins, polychlorinated dibenzofurans, pesticides, phthalate esters, brominated diphenyl ethers, and other hydrocarbons [11]. Pellets of WTC dust were analyzed for chemical functional groups using Fourier Transform Infrared (FTIR) spectrometry.

Polycyclic Aromatic Hydrocarbons (PAHs)

Polycyclic Aromatic Hydrocarbons are organic compounds created during the combustion of organic matter, are made up of multiple fused benzene rings, and are known to be carcinogenic. PAH content was analyzed using the Gas Chromatography-Mass Spectrometry (GC/MS) technique. Each sample was studied for 40 different PAHs, and the total concentrations for all 40 typical PAHs with higher molecular weights were more than 200-300 ug/g. Specifically, in Cortlandt, Cherry, and Market Streets the total PAH concentrations in ng/g were 383,000, 218,100, and 376,100 respectively. The most prevalent PAHs that were detected Fluorene, Phenanthrene, Fluoranthrene, benzo[a]pyrene and benzo[b+k]fluoranthane. The total PAHs in the settled dust and smoke comprised more than 0.1% of the mass. Cortland Street samples, being the closest to the WTC collapse, had the highest concentrations of the PAHs. Researchers assume that the PAH peaks identified in the dust samples were produced from incomplete combustion of building materials, jet fuel from the planes, and the collapse of both World Trade Center towers.

Polychlorinated biphenyls

Polychlorinated Biphenyls (PCBs) are toxic, highly stable organic chemicals that used to be used in industrial settings. 68 PCB congeners (individual compounds) were detected by GC/electron capture, but were not present in excessive levels in the WTC dust.

Polychlorinated dibenzodioxins and Polychlorinated dibenzofurans:

Polychlorinated Dibenzodioxins (PCDDs) are toxic environmental pollutants that are the byproducts of many industrial processes. Their chemical composition is 2 benzene rings connected by two oxygen atoms, and chlorine atoms attached at different points on the rings. Similarly, Polychlorinated Dibenzofurans (PCDFs) are also environmental pollutants and industrial byproducts. Their chemical composition is the same as PCDDs, but instead of the 2 benzene rings being attached by 2 oxygen atoms, the rings are attached with 1 oxygen atom acting as a bridge. Prepared dust and smoke extracts were used to analyze and compare 17 PCDD and PCDF congener concentrations against a standard, via mass spectrometry. The toxic equivalent values for PCDDs and PCDFs were consistent with those found in the dust samples directly from the World Trade Center identified by the U.S. EPA. Both levels of dioxins and furans were below background levels in nature. The PCDD congener found in the highest concentration was the 1,2,3,4,6,7,8,9-OctaCDD with levels (in ng/kg) of 1,450; 3,630; and 3,410 in the three streets. The highest concentration of PCDF congener was 2,3,7,8-TetraCDF, with levels (in ng/kg) of 78.2, 194, and 221.

Pesticides

Pesticides were measured using GC/electron capture detection. No concentrations above background levels were detected for the pesticide chlordane. Specifically, the researchers found 1.9, 0.9, and 1.2 ng/g of hexachlorobenzene in the three streets. The total amount of all the chlorodanes measured was 3.1, 5.6, and 3.7 ng/g in the three streets.

Brominated diphenyl ethers

Brominated Diphenyl Ethers (BDEs) are flame retardants. Their chemical composition is two phenyl rings bonded together with an ether bond, with differing numbers of bromine atoms bonded to the rings. Researchers extracted the dust samples using methylene chloride and the extracts were measured using GC with halogen-selective electrolytic conductivity detection with multipoint calibration and compared against a standard. BDE-47, BDE-99, and BDE-100 are used for polyurethane foam (common as padding in office furniture). The BDE with the highest concentration was BDE-209, with BDE154 + PBB153 being the second highest.

Health Outcomes Post-Exposure to WTC Disaster

Many diseases and health complications arose in World Trade Center responders and survivors. Elevated cancer rates have been found among responders [12,13]. Researchers have found statistically significant elevated levels of thyroid and prostate cancer, as well as an increased risk of cutaneous melanoma and tonsil cancer in subjects exposed to the WTC disaster. Incidence of early stage cancers has also been detected in WTC-exposed responders. Approximately double the prevalence of monoclonal gammopathy, a precursor for multiple myeloma has been detected in two large studies [14,15]. Elevated incidence of mutations in blood cells, a process called clonal hematopoiesis has also been detected in first responders [16]. Clonal hematopoiesis has been shown to lead to increased risk of developing blood cancers.

Another notable effect of WTC exposure was increased lung and respiratory diseases such as WTC cough syndrome, accelerated lung function decline, obstructive airways disease, sarcoidosis, airway hyperreactivity, and obstructive sleep apnea [17-19]. Cardiovascular disease risk was also found to be increased in people exposed to the WTC disaster [20].

Known carcinogens such as dioxins and other inorganic and organic chemicals were found in the WTC dust. These chemicals have been shown to bind to DNA and result in mutations, DNA breaks and translocations. These can result in activation of oncogenes leading to development of tumors. In fact, it has been shown that WTC dust can cause defective DNA replication and introduce pauses that result in higher rate of mutations [16].

Exposure to WTC dust also resulted in massive amounts of systemic inflammation. Inflammatory proteins such as IL-1beta and IL-6 were elevated after exposure and have been shown to stimulate the growth of cancer cells [21]. Inflammation has also been shown to suppress the growth of normal blood stem cells, thus providing selective advantage to mutant cells [22]. Inflammation, due to smoke exposures has also been shown to promote the growth of solid tumors such as lung cancer by activating kinases such as IRAK4 [23]. Thus carcinogenesis can be promoted by various direct and indirect effects that are mediated by exposure to the WTC dust.

The dust exposure also can lead to inflammation in airways and gastrointestinal tracts due to direct exposure by toxic chemicals. Airway hyper reactivity after exposure can accelerate development of asthma and chronic obstructive airway diseases. In fact, rapid decline in lung function was seen in a proportion of first responders after the exposure [24].

The exposure to the WTC disaster particulate matter has resulted in both short term and long-term health consequences for responders as well for residents of lower Manhattan. Various cancers have been shown to be elevated in exposed populations and mechanistic studies have linked various inorganic and organic chemicals to DNA damage and mutations. These studies underscore the effects of environmental exposures on human health that can be felt many years after the event. These studies also call attention to efforts to reduce environmental airborne pollution that can result in worsening of various inflammatory diseases.

Furthermore, identification of toxic substances present in WTC dust support long-term multi-cohort studies incorporating biomarkers to further define chronic disease hazards. Future policy drivers should include hazard evaluation protocols, responder protection policies, and post-disaster remediation protocols to guarantee that future public health impacts are reduced.

We want to thank Dr. Rachel Zeig-Owens and Dr. David Prezant for their outstanding mentorship. We also want to thank Madeline Cannon for providing constructive feedback on the review. Finally, we want to thank all the brave first responders who participated in rescue efforts and various research studies after the WTC 911 disaster.

In the past 2 years Aditi Shastri has received honoraria for educational activities from PeerView , ACHL, Great Debates, HemeOnc Pulse and Geron. Advisory board fees from Kymera Therapeutics, Geron, Ryvu Therapeutics. Research funding from Kymera Therapeutics and Ryvu Therapeutics and is Data Safety Monitoring Board Chair for Servier Pharmaceuticals.

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