LA DIGNIDAD DESDE LA PERSPECTIVA FILOSÓFICA

Nanomaterials in the form of individual particles, agglomerates of nanoparticles, or particles of

nanostructured materials in the air or on the skin constitute the greatest risk to workers (NIOSH, 2006). There are three main exposure routes for workers:

• Inhalation (this is perceived to be the main route for workers). Research among workers has revealed that exposure to aerosols of fine and ultrafine manufactured particles has an adverse effect on lung function and the airways. The role of ultrafine particles in relation to other contaminating substances in these work environments, however, is uncertain in this (NIOSH, 2006);

• Oral exposure. This route receives less attention in the context of occupational health and safety. Some of the inhaled particles however could ultimately be orally ingested. These are particles which end up in the upper respiratory tract and further to transport in the mucus layer are ultimately swallowed. It is unknown whether this is a relevant route for nanoparticles; • Dermal exposure. Little is also currently known about this. Given that this route is relevant in

the work situation, more research in this area is needed.

Workers may be exposed to nanomaterials during the production or synthesis of materials. Table 7.1 shows the possible exposure by production method (see also Section 7.1).

Table 7.1: Potential sources of occupational exposure for various synthesis methods (HSE, 2004). Synthesis

process

Formulation of particles

Exposure source or work activity Primary exposure route

Direct leakage from reactor, especially if the reactor is operated at positive pressure

Inhalation

Product recovery from bag filters in reactors

Inhalation/dermal Processing and packaging of dry

powder

Inhalation/dermal Gas phase In air

Equipment cleaning/maintenance (including reactor evacuation and spent filters)

Dermal (and inhalation during reactor

evacuation) Product recovery from reactor/dry

contamination of workplace

Inhalation Processing and packaging of dry

powder Inhalation/dermal Vapour deposition On substrate Equipment cleaning/maintenance (including reactor evacuation)

Dermal (and inhalation during reactor

evacuation) If liquid suspension is processed into a

powder, potential exposure during spray drying to create a powder, and the processing and packaging of the dry powder

Inhalation/dermal Colloidal/attrition Liquid

suspension

Equipment cleaning/maintenance Dermal

Note: Ingestion would be a secondary route of exposure from all sources/activities from deposition of nanomaterials on food or mucous that is subsequently swallowed (primary exposure route inhalation) and from hand-to-mouth contact (primary exposure route dermal). Ocular exposure would be an additional route of exposure from some sources/activities from deposition of airborne powders or mists in the eyes or from splashing of liquids.

As the above table shows, there are various possible sources and routes of exposure with each production process. Work activities for the purpose of packing, transferring or cleaning offer possibly the greatest source of exposure. The production itself may be expected to result in relatively less exposure because this often takes place in closed systems.

In gas phase processes there is the possibility of inhalation exposure when leakage occurs, certainly when this involves a process under pressure. The type of aerosol that could be released will depend on the phase in the production process in which the leak occurs (HSE, 2004).

Inhalation exposure can also take place during the recovery of the product. For example, particles produced in certain processes are captured in a filter. Poorly functioning filters could lead to the release of particles in the work environment, for example. The potential exposure will depend on the properties of the process and of the product (HSE, 2004). About this the NIOSH (National Institute for

Occupational Safety and Health) has the following to say:

‘In general, it is likely that processes generating nanomaterials in the gas phase (after removal of the nanomaterial from an enclosed generation system), or using or producing nanomaterials as powders or slurries/suspensions/solutions (i.e., in liquid media), pose the greatest risk for releasing nanoparticles.’

The maintenance of production systems (including cleaning and the removal of materials from the extractor) could possibly also lead to exposure (NIOSH, 2006).

Furthermore, occupational exposure can occur during the transport, formulation, end use and waste processing or recycling of products. The diagram in Figure 7.1 shows in which parts of the

production/use chain for manufactured nanoparticles moments of exposure can occur.

Production of

nanoparticle nano-_product

Emptying of packages dispersion Endproduct with nanoparticles Down-stream user e.g. coating of surfaces

by different application methods

Down-stream user nano-product

Application

Example: Produced nanoparticles and coating products

Coated surface

Processing or treatment Wearing

Figure 7.1: Diagram of the production and use chain for a coating containing nanoparticles.

The nanoparticles are produced in the first part, the nanoproduct is incorporated in the coating in the second part, and finally the coating is applied once more. In all parts there may be potential exposure to nanoparticles, although the form, nature and degree of exposure will differ per link in the chain. The following work activities involve a possibility of exposure to nanoparticles:

• The transfer of nanoparticles (e.g., powders) from the packaging to a mixing vessel or reactor (inhalatory exposure);

• Filling (liquid) product which contains nanoparticles (dermal);

• The processing/use of a product that contains nanoparticles (depending on method of use, dermal and/or inhalatory);

• Mechanical treatment of surfaces (e.g., sanding) to which a product containing nanoparticles has been applied (inhalatory);

• Maintenance and cleaning of equipment and processes in which nanomaterials are

manufactured or the cleaning of extraction systems and waste material or ‘spilled’ material (dermal and/or inhalatory).