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Toxicological information

Health surveillance data

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Administrative data

Endpoint:
health surveillance data
Type of information:
other: human data
Adequacy of study:
supporting study
Reliability:
other: not rated acc. to Klimisch
Rationale for reliability incl. deficiencies:
other: Well-documented health surveillance case study

Data source

Reference
Reference Type:
publication
Title:
A health surveillance case study on workers who manufacture silver nanomaterials
Author:
Lee, J.H et al.
Year:
2012
Bibliographic source:
Nanotoxicology 6(6), 667 - 669

Materials and methods

Study type:
biological exposure monitoring
Endpoint addressed:
repeated dose toxicity: inhalation
Test guideline
Qualifier:
no guideline followed
Principles of method if other than guideline:
A health surveillance study was conducted in a workplace which manufactures silver nanomaterials, including the assessment of personal exposure levels to silver nanoparticles, a walk-through evaluation of the manufacturing process and the collection of blood and urine samples from two exposed workers who had worked for 7 years in the business of manufacturing silver nanomaterial.
GLP compliance:
not specified

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid: nanoform
Details on test material:
- Name of test material (as cited in study report): silver nanoparticles (<100 nm)

Method

Type of population:
occupational
Ethical approval:
not specified
Details on study design:

SUBJECTS:
2 workers participated in the voluntary biomonitoring program. The workers were 37 and 42 years of age, male, and had worked for 7 years in the nanosilver manufacturing industry.

WORKPLACE DESCRIPTION:
A large-scale pilot reactor was used to manufacture silver nanoparticles <100 nm in size at a rate of 5 kg/day. Various types of precursor (wire type, powder type, liquid type) were fed through an inductively coupled plasma (ICP) torch, where the precursors were vaporised in the argon plasma. This vaporised precursor gas was then moved through a second zone of plasma produced from a passive ICP RF-antenna. In this zone, the atoms were condensed to nanoscale particles using a specific temperature gradient and cooling process. From the precursor feeding to the nanopowder collection, all the processes were conducted in a vacuum state. The connection from the reactor to the collector was a complete closed system, and thus very few silver nanoparticles were released from the collector into the workplace air. Silver nanoparticles ranging from 20 to 30 nm and manufactured as silver powders were introduced to the reactor using a torch and reacted with acetylene and oxygen gases. The manufactured silver nanoparticles were then amassed in a collector.

PERSONAL SAMPLING:
The air samples were taken by drawing air through mixed cellulose ester filters in sampling cassettes (37 mm diameter, 0.8 mm nominal pore-size, and 2 in. cowl) obtained from Pall Corp. (P/N 64678; Ann Arbor, MI). The filter samples for personal sampling were collected in the breathing zone using MSA (Escort Elf pump)-operated sampling pumps at a flow rate of 1.5–2.0 L/min and SKC (Leland Legacy pump)-operated sampling pumps at a flow rate of 6.9–7.3 L/min when the work duration was short. The sampling holders were also changed during the sampling period to avoid overload. The sampling with personal samplers was performed during the normal work period from 09:30 to 16:00 and typically lasted 159–350 min. The personal samplers were attached to the workers involved in the nanomaterial manufacturing. The total suspended particulate concentration was determined gravimetrically based on the NIOSH manual of analytical methods (NMAM) 0500 (1994)*.

SILVER ANALYSIS:
Silver concentrations on the filter were analysed using an ICP (Perkin Elmer optima 5300DV) based on the NMAM 7300-ICP method (NIOSH, 2003)* after wet digestion using the ICP-OES Plasma Spectrometer method. The filters were digested in a microwave (MARS Xpress, CEM) for 15 min at 150°C in the presence of nitric acid. After digestion, the samples were allowed to cool and analysed by ICP.

COLLECTION AND ANALYSIS OF BIOLOGICAL SAMPLES:
Urine and blood samples from 2 workers were collected after their shift. The analysis of the blood samples included the blood biochemistry and a haematological examination. The blood and urine were digested with concentrated nitric acid using the microwave digestion system (MARS 230/60, CEM). The concentration of silver in the digested fluid was then analysed by a flameless method using an atomic absorption spectrophotometer equipped with a Zeeman graphite furnace (Perkin Elmer 5100ZL, Zeeman Furnace Module, USA) based on the NIOSH 7300 method (2003)*.The concentration of silver in the tissue was expressed as µg/dl wet weight.

*References
- National Institute for Occupational Safety and Health (NIOSH), Manual of Analytical Methods (NMAM). 1994. Particulates not otherwise regulated, 0500. Cincinnati: NIOSH.
- National Institute for Occupational Safety and Health (NIOSH), Manual of Analytical Methods (NMAM). 2003. Elements by ICP 7300 (Nitric/Perchloric Acid Ashing). 4th ed. Cincinnati: NIOSH.

Results and discussion

Results:
Two male workers who had worked for 7 years in the business of manufacturing silver nanomaterial were exposed to silver concentrations of 0.35 and 1.35 mg/m3. The blood and urine levels of silver were 0.034 and 0.0135 mg/dl for blood and 0.043 mg/dl and not detected level for urine. The blood chemistry and haematology data were determined to be within a normal range. Taken together, the health surveillance indicated that the nanomaterial manufacturing workers were exposed to a much lower concentration of silver dust or soluble silver threshold limit values and showed no significant findings on their health status.

Any other information on results incl. tables

Table 1: Demographic data and silver concentrations related to personal exposure, and blood and urine samples

Worker

Gender/age

Occupational history (years)

TSP (mg/m3)

Air Ag (mg/m3)

Blood (µg/dL)

Urine (µg/dL)

1

Male/37

7

0.15755

0.00035

0.034

0.043

2

Male/42

7

0.10869

0.00135

0.030

ND

Applicant's summary and conclusion