April 2000
ATLANTA - A possible association between acute pulmonary hemorrhage/hemosiderosis in infants and exposure to molds as a result of water damage has not been established, according to an update by the Centers for Disease Control and Prevention (CDC).
The mold under investigation by the CDC following flooding in Cleveland in the early and mid-1990s was Stachybotrys chartarum commonly referred to by its synonym Stachybotrys atra.
The clarification "is a result of an internal and external review process," said Stephen C. Redd, MD, chief of the Air Pollution and Respiratory Health Branch in the National Center for Environmental Health at the CDC. "Based on the review, the association of exposure to S. chartarum and pulmonary hemorrhage is not established. This is our revised opinion." However, "I don't think our revised opinion changes the recognition that there are health effects from exposure to mold."
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The review process took more than two years to complete. Reports of the possible association date back to 1994. In December 1994 and January 1997, articles in the Morbidity and Mortality Weekly Report described a cluster of 10 infants from Cleveland with acute idiopathic pulmonary hemorrhage, also referred to as pulmonary hemosiderosis. The children, who all resided in seven contiguous postal tracts, had one or more hemorrhagic episodes during January 1993-December 1994. These episodes resulted in one death.
Preliminary results of a CDC case-control study indicated that hemorrhage was associated with major household water damage during the six months before illness and increased levels of measurable household fungi, including the toxin-producing mold S. chartarum.
---Stachybotrys
atra
In hindsight, "there were problems with data collection, data analysis and reporting," Redd said. For instance, although sampling was to be blinded, "one investigator knew the identity of many case homes." Because this investigator wanted to ensure the identity of culturable fungi, he collected twice the number of air samples from case homes as from control homes.
"There obviously was a lack of a standardized protocol," Redd said. "But I don't think the intent was to deceive either. The investigator was operating with the best of intentions."
Nonetheless, investigators used aggressive, nonstandardized methods to generate artificial aerosols for sampling, including vacuuming carpets and pounding on furnace ducts and furniture. "This increased the potential for differential exposure assessments of cases and controls if sampling were conducted in an unblinded manner," Redd said.
The reviewers found that the reported odds ratio of 9.8 for a change of 10 cfu/m3 was statistically unstable and potentially inflated. "Small changes in the statistical approach produced big effects in the estimate of the association in each of these cases and in a less strong association than what was originally reported," Redd said.
There were also concerns about characterizing the clinical problem as "hemosiderosis" because of the acute presentation in all 10 cases, the narrow age distribution (6 weeks to 6 months) and the absence of iron deficiency. "These factors suggest that the illness described in Cleveland is clinically distinct from idiopathic pulmonary hemosiderosis, which is the condition to which this cluster was linked," Redd said.
Furthermore, "Stachybotrys didn't appear to be associated with water damage in the way water damage was classified," Redd said. Among homes classified as water damaged, the presence of any culturable airborne S. chartarum was identified in similar percentages of case and control homes (four of eight compared with three of seven). Although the numbers were small, "this provided little evidence of a difference in the presence of airborne S. chartarum between water-damaged case and control homes," Redd said. "If the classifications of water damage were correct, this would suggest that water damage, or an unrecognized correlate of water damage, may be confounding any perceived association with S. chartarum."
Finally, the mold-disease association observed in the Cleveland investigation was not observed in the subsequent Chicago investigation of a similar cluster.
For more information:
- CDC. Update: pulmonary hemorrhage/hemosiderosis among infants - Cleveland, Ohio, 1993-1996. MMWR. 000;49(09);180-4.
- CDC. Acute pulmonary hemorrhage/hemosiderosis among infants - Cleveland, January 1993-November 1994. MMWR 1994;43:881-83.
- CDC. Update: pulmonary hemorrhage/hemosiderosis among infants - Cleveland, Ohio, 1993-1996. MMWR. 997;46:33-5.
- Etzel RA, ed. Handbook of Pediatric Environmental health.Elk Grove Village, Illinois: American Academy of Pediatrics, 1999.
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