Study reveals that suggested threshold limit values are from two to fifty times lower than current recommended threshold limit values. Proposed safe limits of exposure to the ultrafine dusts are based on known toxic potential of various materials as determined in particle size ranges

Boylen, G. W., Jr.

Chamberlin, R. I.

Viles, F. J.

English

NASA Technical Reports Server

August 1969
	
Brief 69-10268 
NASA TECH BRIEF	
_1a 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Health Hazards of Ultrafine Metal and Metal Oxide Powders 
Facilities that handle ultrafine metal and metal 
oxide powders will be interested in knowing that 
a comprehensive study has been made and an excel-
lent report has been issued appraising special health 
hazards associated with, and the control of, ultra-
fine metal and metal oxide operations. Materials 
studied included nickel, tungsten, thorium oxide, 
aluminum and aluminum oxide, magnesium oxide, 
zirconium oxide, niobium, molybdenum, cobalt, and 
chromium. 
The studies were conducted specifically for powder 
metallurgy work at the NASA Lewis Research Cen-
ter, but are believed to be generally applicable to 
other operations generating respirable fine dusts 
which can be toxic. Proposed safe limits of exposure 
to the ultrafine dusts were based on the known toxic 
potential of the various materials as determined in 
more conventional particle size ranges and a theo-
retical consideration of the effects due to the smaller 
particle sizes. 
Toxicological data available in the literature were 
reviewed. Tentative threshold limit values for occu-
pational exposures to ultrafine dusts were proposed 
based on the assumption that all particles in an air 
sample might be individual particles and might exert 
their physiological effects as individual particles when 
inhaled. These suggested threshold limit values are 
from two to fifty times lower than current threshold 
limit values recommended by the American Confer-
ence of Governmental Industrial Hygienists. The pro-
posed levels reflect the potential increase in toxicity 
of the materials due to their existence in the ultra-
fine powder state. 
Experimental studies dealing with electron micro-
scopy, particle size, aerosol generation and sampling,
degree of agglomeration, and nature of airborne con-
taminants including pyrophoricity and effective par-
ticle size were conducted. Results indicated that the 
test metal and metal oxide powders when airborne 
are highly agglomerated with 95 percent or more of 
the weight of the airborne substances represented by 
particle agglomerate sizes greater than 0.1 micron in 
diameter. 
An industrial hygiene survey of laboratory work 
areas was made. Operations and operational prac-
tices were thoroughly reviewed. Air monitoring 
samples were obtained as well as urine samples from 
the personnel working in the area. These samples 
were then analyzed using chemical techniques devel-
oped or revised specifically for this project. Ana-
lytical results of the dusts collected during air 
sampling demonstrated that air monitoring was essen-
tial for the control of dust levels. Detailed analytical 
and air monitoring procedures were furnished. Based 
on this survey, control measures for all operations 
were recommended. To complete the study, medical 
aspects were included; a continuing industrial hygiene 
and surveillance program was outlined; and recom-
mendations for future toxicological research were 
made. 
Notes: 
I. The NASA Lewis Research Center has found this 
study useful in establishing guidelines for the
operations and handling of fine powder materials. 
During several years that operations with these
powders have been carried out, no clinical signs 
of chemical toxicity have been detected in any of
the operating personnel. The chemical monitor-

ing developments have been particularly useful. 
Analysis has shown that the operating practiáes 
(cOnInued overleal) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19690000268 2020-03-16T17:48:07+00:00Z
recommended have been effective in controlling 
dusts produced during various operations. 
2. Documentation is available from: 
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Price $3.00 
Reference: TSP 69-10268 
3. Technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B69-10268
Patent status: 
No patent action is contemplated by NASA. 
Source: F. J. Viles, R. I. Chamberlin, 
and G. W. Boylen, Jr. of 
Viles, Chamberlin, and Boylen 
Norwood, Massachusetts 
under contract to 
Lewis Research Center 
(LEW-10878) 
Brief 69-10268	 Category 04


Health hazards of ultrafine metal and metal oxide powders

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