Nano-dust and the CEN guidelines

In this article, we will touch on Nano-dust CEN guidelines. Many European industries produce and use nanomaterials, including those in chemical manufacturing. These materials must comply with both EU regulations and national laws. Employers must provide workers with the knowledge and equipment needed for safe handling.

Nanotechnology produces a wide range of products, which can expose many workers to nanomaterials. Although nanomaterials are often produced in closed systems, exposure can still occur. Workers may encounter these materials during maintenance tasks or while handling finished products.

Legislative guidelines are essential for safe handling and management of nanomaterials in the workplace. The European Union is actively advancing new technical standards for nanomaterials, which include methods to assess workplace exposure. To achieve this, the European Commission issued a specific directive for developing nanomaterial standards in occupational settings. Several technical committees, including the Comité Européen de Normalisation (CEN), are working to fulfill this mandate.

In February 2019, CEN introduced the NEN-EN 17199-4:2019, commonly known as EN 17199-4. This document provides guidance for measuring the dustiness of bulk materials that may contain or release respirable NOAA or other fine particles in workplace environments. Part 4 specifically details the small rotating drum method, a technique used to evaluate potential exposure to nano-dust in workspaces.

NOAA, which stands for engineered nano-objects and their aggregates and agglomerates, have a wide range of applications in various industries. These structures are on a scale comparable to viruses, molecules, or even atoms. NOAA appear in many industrial processes, such as silver nanoparticle synthesis, thin nanocarbon layer production, and 3D printing using nanohydroxyapatite-polymer composites.

Despite their benefits, engineered nanomaterials also pose potential health risks due to their toxicity. Human exposure to NOAA can theoretically occur at any stage of the material lifecycle, but it’s most likely in workplaces where these materials are produced or handled extensively. Because NOAA particles are typically around 100 nanometers in diameter, they can easily be absorbed through the skin or inhaled.

In the workplace, inhalation is a primary exposure route. Once inhaled, NOAA particles can penetrate deep into the respiratory system, potentially entering the bloodstream and even crossing the blood-brain barrier. These nano-sized compounds can accumulate in organs, where they may interfere with basic cellular functions like metabolism, proliferation, and differentiation. Ensuring safe handling and minimizing exposure to NOAA are essential to protecting worker health.

Airway examinations typically involve three main types of tests:

1. Spirometry: This test measures how much air you can move in and out of your lungs, assessing lung function and airflow.
2. Body Box (Plethysmography): This test evaluates the resistance of your airways and measures lung volume, providing insights into how your airways and lung contents respond to breathing.
3. Diffusion Test: This test examines how well your blood absorbs oxygen from your lungs, helping assess the efficiency of gas exchange in the lungs.

Each of these tests provides crucial information about respiratory health and function.

When measuring nanoparticles, a common issue is the non-specificity of many instruments. These tools often cannot differentiate engineered nanoparticles from naturally occurring or environmental nano-sized particles, leading to potentially inaccurate results. To address this, experts developed a three-tiered approach based on a systematic review of previously proposed methods and assessments. This structured approach aims to improve measurement accuracy and distinguish between different types of nanoparticles.

However, the EN 17199-4 guideline adopts a distinct approach. Instead of focusing on classification, EN 17199-4 offers specific methods for assessing dustiness in materials that release respirable particles, including nano-objects. This guideline provides standardized protocols, enhancing workplace safety by helping to evaluate and control potential exposures.

The EN 17199-4 provides clear guidelines for measuring and characterizing dustiness, helping manufacturers assess potential dust emissions during material handling, processing, or storage. These guidelines offer critical information that can aid manufacturers and handlers in reducing dust emissions and establishing safe handling practices for NOAA (nano-objects and their aggregates/agglomerates) materials.

The small rotating drum (SRD) method, as described in EN 17199-4, is specifically designed to mimic workplace scenarios. It represents general bulk material handling activities such as pouring, mixing, scooping, dropping, and tipping. This method differs from others, like the standard rotating drum, continuous drop, and vortex shaker methods, as it repeatedly pours and agitates bulk materials to simulate real handling processes.

The SRD method in EN 17199-4 measures dustiness based on several key parameters:

• The respirable dustiness mass fraction
• The number-based dustiness index
• The number-based emission rates
• The time required to generate 50% of the emitted particle numbers

These measurements provide comprehensive insights into the dustiness of bulk materials, helping industries manage workplace exposure risks and enhance safety protocols.

Although the EN 17199-4 provides a standardized method for nano-dust measurement, no commercially available instruments currently meet these specific needs. In collaboration with Professor Dr. Keld Alstrup Jensen, one of the principal writers of EN 17199-4, we are developing a new nano-dust measuring technology based on the standard’s methodology. We anticipate launching this setup in 2021. If you’d like updates on this development, feel free to send us an email.

The small rotating drum (SRD) method outlined in EN 17199-4 has been successfully applied to test powders, granules, and pellets that contain or release respirable NOAA (nano-objects and their aggregates/agglomerates) and other respirable particles in unbound, bound uncoated, and coated forms.

This method has enabled effective dustiness testing for a wide variety of materials, including nanoparticle oxides like TiO₂ and SiO₂, nanoflakes, organoclays, clays, carbon black, graphite, carbon nanotubes, organic pigments, and active pharmaceutical ingredients. The SRD method thus offers a robust approach for testing materials containing nanomaterials as primary components, supporting safe and standardized handling practices in diverse industrial applications.