Key messages

• Human biomonitoring is critical for accurately assessing welders’ exposure, as it captures internal doses and early biological effects that cannot be quantified by traditional air monitoring alone.
• Welding fumes are complex carcinogenic mixtures of ultrafine particles, requiring integrated exposure assessment approaches to better understand and manage associated health risks.
• Combining biomonitoring with direct-reading instruments enables more precise, real-time exposure assessments and supports improved occupational heath risk assessment and regulatory policies.

Overview

Human biomonitoring is essential for assessing exposure to welding fumes, as it reflects internal doses by measuring metals (e.g., Pb, As, Cd, Hg, Ni, Cr) and early-effect biomarkers such as immune and neurotoxic responses. This is crucial for welders exposed to complex mixtures of ultrafine particles that penetrate deep into the lungs and pose potentially significant health risks, including cancer, endocrine disruption, neurotoxicity, respiratory diseases, and other chronic conditions linked to metal deposition and tissue damage.

Absorption depends on aerosol properties (size, surface area, solubility), metal speciation, welding techniques, and individual physiological factors. In contrast, air monitoring captures only external exposure and cannot account for interindividual variability. Direct-reading instruments ↗ (DRI’s) offer real-time characterization of fume fluctuations across tasks and ventilation conditions, but interpretation is limited by calibration uncertainties and chemical non-specificity. Integrating biomonitoring with DRIs enables correlations between air measurements and internal dose, as DRIs can function as early warning tools.

Aligned with PARC priorities, this project aims to improve the chemical risk assessment of welding fumes, classified as carcinogenic to humans, and address key regulatory challenges. It also provides information on the sensitivity of various biomarkers to detect exposures and early effects at the exposure levels that are below the modern Occupational Exposure Limit values (OELs).

The proposed project aims to develop standardized and robust methods for monitoring, including human biomonitoring and direct reading instruments, and testing these methods in field studies, which will generate ~4,000 biological and air samples from 840 participants across industries.

Policy relevance

The project will develop recommendations for Occupational Exposure Limits (OELs) for welding fumes and support their inclusion in the Carcinogen, Mutagens, and Reprotoxic (CMR) Directive ↗. Traditional gravimetric air sampling using inhalable fraction samplers, which is the basis for current OELs, will be applied in field studies to provide reference measurements for validating direct-reading instruments (DRIs). While respirable fractions may be explored for research purposes, regulatory comparisons will focus on the inhalable fraction, consistent with existing frameworks.

This project will generate biomonitoring data on welders that directly supports the refinement of EU Occupational Exposure Limits (OELs) under the Chemical Agents Directive (98/24/EC) ↗, particularly for metals such as chromium, manganese, and cadmium. By providing internal exposure data, it addresses regulatory gaps where air monitoring alone is insufficient. The data will also inform the development of Biological Limit Values (BLVs) by ECHA RAC and contribute to the implementation of EU-OSHA and OECD guidance on occupational biomonitoring, thereby advancing harmonized and evidence-based worker protection policies across Member States.