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Monitoring shows plumes of carcinogenic formaldehyde in neighborhoods along Houston’s Ship Channel

Air pollution monitoring by the Houston Health Department in 2019 and 2020 recorded levels of formaldehyde, a known carcinogen, along the Houston Ship Channel that pose potential health risks to surrounding neighborhoods.

The analysis, funded by the US Environmental Protection Agency, found that from 27 September 2019 to 26 September 2020, formaldehyde concentrations at three monitoring sites exceeded EPA’s health screening level of 0.17 parts per billion. Concentrations never exceeded thresholds set by the Texas Commission on Environmental Quality (TCEQ).

The people most at risk are primarily low-income, Latino and Black residents of Manchester, Harrisburg, Meadowbrook, Allendale, Northshore, and Galena Park just across the fence lines from oil refineries, plastics plants, and other industrial facilities.

Experts have known for decades that the neighborhoods along the Houston Ship Channel face increased cancer risk from a toxic mixture of air pollutants from industry and traffic. According to the 2014 NATA, formaldehyde is the highest contributing chemical to cancer risk in nearly 89% of census tracts in Harris County.

Formaldehyde is difficult to regulate and control in Houston because the vast majority is formed from other pollutants and multiple sources. In addition to contributing to cancer risk, formaldehyde reacts secondarily to form ground-level ozone, a respiratory irritant responsible for increased rates of cardiac arrest and asthma. The Houston Health Department’s research contributes to the understanding of these critical air pollutants allowing for improved modelling and regulation efforts by the Texas Commission on Environmental Quality and EPA.

…The vast majority of ambient formaldehyde along the Houston Ship Channel originates from chemical reactions involving formaldehyde precursors which are predominantly emitted from the petrochemical industry.

The Health Department’s highest measurements were in the Cloverleaf neighborhood, where monitoring averaged 2.28 parts per billion of formaldehyde—more than 13 times EPA’s health screening level. In the long-term, this would translate to about 1 additional cancer case per 77,000 people, according to the Houston Health Department’s assessment of EPA’s cancer risk formulas.

Formaldehyde is a colorless, flammable gas to which brief exposure can cause irritation of the skin, eyes, nose, and throat. It also contributes to ground-level ozone, which can cause damage to the lungs and increased rates of cardiac arrest and asthma.

Long-term exposure to formaldehyde can cause certain types of cancers. While formaldehyde is regulated for its use in construction materials and household products, elevated levels of ambient, or airborne, formaldehyde in urban environments remains a public health threat.

Most of the formaldehyde along the Houston Ship Channel originates from chemical reactions involving formaldehyde precursors that are predominantly emitted from the petrochemical industry, according to the report. Less than 5% of the formaldehyde present in Houston’s air is emitted directly from industrial point sources, and about 4% is from vehicle emissions.

Secondary formaldehyde (i.e., not directly emitted but formed by the combination of other air chemicals in the air) makes up more than 90% of all the formaldehyde present in Houston Ship Channel neighborhoods. Formaldehyde precursors include ethylene, propylene and other volatile organic compounds.

The report makes the following recommendations:

  • New regulations and mechanisms—such as stronger permits—are needed to reduce the chemicals such as ethylene and propylene that are emitted from industrial sources and lead to secondary formaldehyde formation.

  • TCEQ could consider amending its “Highly Reactive VOC” rules to address the problem of formaldehyde air pollution associated with secondary formation from gases such as ethylene, isoprene, and propylene.

  • Federal and state authorities may wish to consider increased formaldehyde monitoring and make any subsequent analysis widely available so that public health risks can be better understood and controlled. Increased monitoring can better inform regulators and legislators on the impact of these atmospheric pollutants.


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