Short-Term Exposure to Nitrogen Dioxide

Our plain-English summary of Short-Term Exposure to Nitrogen Dioxide, by A.R. Dowell, K.H. Kilburn, P.C. Pratt (1971).

The study

• Authors: A.R. Dowell, K.H. Kilburn, P.C. Pratt
• Published: Archives of Internal Medicine, Volume 128. July 1971
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This article is not about asbestos. It reports an experiment on nitrogen dioxide (NO2), a gas. The authors exposed 11 anesthetized beagle dogs on a respirator to nitrogen dioxide at 3 to 16 parts per million (ppm) for one hour, and two control dogs were ventilated with air. Exposure to 7 to 16 ppm was frequently associated with acute pulmonary edema (fluid in the lungs) within 60 minutes, with low blood pressure and reduced cardiac output. When the air sacs held fluid, the lung wash material had an impaired ability to lower surface tension. Static lung compliance was abnormal in three of four such studies. Five dogs exposed to 3 to 12 ppm showed cell membrane damage without fluid in the air sacs and no appreciable blood-circulation changes. At 3 ppm there were no blood gas, compliance or surfactant changes. The authors concluded that the critical one-hour concentration in this dog model appeared to be about 5 ppm, supporting the 5 ppm industrial limit for short-term exposure. They noted that extrapolating from anesthetized dogs to humans is questionable.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: animal experiment (short-term inhalation exposure in dogs)
• Who was studied: 13 beagle dogs weighing 8 to 13 kg, anesthetized: 11 exposed to nitrogen dioxide and 2 controls ventilated with air for one hour; place and dates of the experiments not stated
• Exposure: nitrogen dioxide (NO2) mixed in compressed air at selected concentrations from 3 to 16 ppm for one hour (not asbestos)
• Main results:
  • In dogs exposed to 7 to 16 ppm, exposure was frequently associated with acute pulmonary edema within 60 minutes
  • In these dogs, low blood pressure (hypotension) came with a decrease in cardiac output and stroke volume
  • Static lung compliance was abnormal in three of four studies with obvious intraalveolar edema
  • Lung wash material had an impaired ability to lower surface tension when intraalveolar edema was present, whatever the NO2 concentration; normal dog surfactant exposed to NO2 in the test tube kept its ability to lower surface tension
  • Five dogs exposed to 3 to 12 ppm showed cell membrane damage without intraalveolar edema and no appreciable hemodynamic changes
  • 3 ppm NO2 did not produce hemodynamic, blood gas, surface tension, compliance or surfactant changes
  • Under the electron microscope, one-hour exposure to 3 to 12 ppm damaged cell membranes and mitochondria; swelling was scattered at 3 ppm and more general at higher exposures
  • The authors reported that as little as 7.5 ppm NO2 for one hour produced acute intraalveolar edema in the model
• The authors' conclusion: The authors concluded that the critical one-hour NO2 concentration in this dog model appears to be about 5 ppm, and that the data support the present industrial threshold limit of 5 ppm at least for short-term exposure
• Limitations the authors state:
  • Extrapolating from this anesthetized dog model to humans is questionable
  • Anesthesia and positive pressure breathing from a respirator may have made the distribution of inhaled gas more uniform than in normal breathing
  • Differences in exposure technique and host factors from dog to dog may explain varying degrees of tissue damage
  • Poor recovery of lung wash lipid from some lungs is not fully explained, and the authors said further studies are needed

Topics

Medical terms in this study, explained in our Lexicon: Short-Term Exposure, Respirator.

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