WTC environmental investigation report, Sep 2002

NYC 9/11 Public Portal Document

Final Technical Report of the Public Health Investigation Page 22 of 56 sidewalks). Indoor settled surface dust may have been reduced if appropriate cleaning had been conducted prior to this sampling event. Therefore, these results serve as estimates, and are not necessarily reflective of conditions at earlier time points or of current conditions.

■ Likewise, if continued cleaning has occurred since the November-December 2001 sampling event, levels of contaminants should be lower today. Therefore, the results of this sampling effort would tend to overestimate the current levels of WTC-related materials in the buildings.

Uncertainty also exists in determining at what level and duration of exposure people might experience irritation or other symptoms from exposure to fibers and crystalline minerals.

• The likelihood of experiencing irritation from individual contaminants or contaminant mixtures is uncertain. A short exposure to a small amount of an irritant may be tolerated, but exposures that continue for a longer period of time or are to a larger amount of an irritant, may overwhelm the body's ability to remove the irritant and increase the likelihood of irritation. Individual differences also play a significant role in whether or not irritation occurs. Using a risk estimate from an occupational situation may underestimate risks for more sensitive or susceptible individuals in the general population. Some of the information needed to estimate the risk of irritant symptoms, is not available from this study. When assumptions are made in the absence information (e.g., the duration and intensity of the total exposure) additional uncertainty is introduced.

• Persons with pre-existing respiratory (e.g., asthma, emphysema) or cardiopulmonary problems are more likely than healthy individuals to experience adverse health symptoms at lower levels of airborne particles and contaminants. Airborne dust and crystalline mineral levels based on studies of healthy individuals are levels that underestimate the risk for a susceptible individual.

• Individuals who were in the lower Manhattan area when the WTC collapse occurred may have received a bolus inhalation dose of dust, fibers, crystalline minerals, and other materials. Health effects of a bolus dose are not known. Additional exposures would add to the potential for health effects. Therefore, the short and long-term health effects, if any, of such an exposure cannot be determined from the measurements made in this study.

RESULTS

This section of the report will provide an overview of what was determined by this investigation. The overall analytical findings will be presented according to what environmental media was sampled (air or settled surface dust. Figures 7-17).

A. Survey

The primary duty of the sampling team was to coordinate with the building management to identify sampling locations that would

http://www.atsdr.cdc.gOv/asbestos/lowermanhattan/ResSamp_Sep2002_Text.html 07/18/2003 NYC-WTC_000178409