There is an urgent need for a proactive approach to identify future risks of chemicals to workers’ health and safety in a continuously changing world of work. There may be unknown and unexpected risks, and early warnings may prevent later high consequences in terms of adverse health effects and socio-economic impacts (see also “Late lessons from early warnings”). This argues for a complementary approach based on the occurrence of disease and inductive reasoning towards new risk factors in work. We call it the ‘disease first’ approach; an approach based on secondary prevention.
Issue and scope of the problemNew and Emerging Risks of Chemicals (NERCs) continue to emerge despite all regulations. Currently, Occupational Safety and Health (OSH) regulations are based on risk assessments of chemicals by the identification of hazardous substances used, assessing inhalation and dermal exposure, comparing exposure with occupational exposure standards, and subsequently reducing exposure when applicable. This is the preferable approach since it is based on primary prevention; we call it the ‘exposure first’ method. It is based on the premise that all necessary toxicological information of substances is available. However, chemical classification is often based on oral exposure data, which is the least important exposure route for workers. This was, for instance, a problem regarding inhalation exposure of workers to the flavouring agent diacetyl used in the food industry (popcorn industry, bakeries, dairy products, and coffee). Oral exposure is perfectly safe but inhalation exposure may cause a potentially lethal lung disease. Besides exposure to substances with unknown toxicological health effects, workers may also be exposed to substances with known toxicological effects in a branch of work with poor access to this toxicological information. For example, in mining and ceramics, it is well known that exposure to crystalline silica may lead to silicosis. However, after applying sand blasting techniques in the clothing industry, many workers were diagnosed with silicosis. At this moment, cases of silicosis are reported in dentists and dental technicians caused by alginate, which contains amorphous silica that is transformed into crystalline silica at high temperatures.
Challenges and opportunities facedSince the approach of risk assessment and management is not sufficient in preventing employees from work-related ill health, we need complementary information from ‘the field’. The ‘disease first’ method is an inductive way of reasoning, starting with observations of health effects in workers and trying to identify causal factors. In this way a disease can act as an early warning. This warning can be collected in ‘Early Warning Systems’ (EWS) comparable with the ones used in pharmacovigilance to detect and evaluate adverse health effects of drugs after introduction to the market. In the author’s opinion the application of EWS in the occupational setting can ultimately reduce the number of work-related diseases. Generally, EWS are based on two approaches (1) spontaneous reporting of cases by vigilant physicians, other health care workers and/or workers using a clinical watch system, and (2) research in existing databases.
The success of the disease first method depends on the vigilance of health professionals and workers. In a successful ‘disease-first’ approach, the cases of potential work-related health effects are collected in a clinical watch system. Next, these cases should be evaluated for potential causal relationships, preferably in expert groups, comprising occupational physicians, medical specialists, industrial hygienists, toxicologists, epidemiologists and statisticians. After the identification of a potential NERC, the signal is strengthened and verified by finding additional cases, e.g. in existing databases or using networks. International cooperation in the identification and strengthening of NERCs is essential to let the system work, since information both on health effect(s) and occupational exposure is needed to determine a causal, or at least plausible, relationship. Workers are often exposed to many substances and incidences of emerging health effects are often low which makes it difficult to establish a causal relationship. Furthermore, existing national databases on both exposure and health effects cannot easily be shared because of privacy and technical reasons. Collaboration between the owners of these databases will bring the identification of potential NERCs further. The MODERNET* network is an international network of mainly European professionals who evaluate and discuss NERCs for workers and share knowledge with each other with the aim of rapidly exchanging information on potential new work-related diseases between European countries and introducing measures to reduce the risk.
Several actions are possible if there is sufficient evidence for a potential NERC to become a verified NERC:
- When health effects are reported below an occupational exposure limit (OEL), which was the case for diacetyl, a request for re-evaluation of the OEL is needed;
- Professionals in occupational health and safety should be informed, e.g. via an alert;
- If a substance is already under evaluation, e.g., under REACH in Europe, this should be communicated;
- If a substance is not yet regulated, options to further regulate the concern should be investigated. In the past years, several NERCs were evaluated e.g. tricobalt tetraoxide and indium tinoxide. For tricobalt tetraoxide the initiative led to an adaptation of the composition of the substance. For indium-tinoxide it was concluded that users of the substance should be informed about the concern.
Concluding recommendationsThe ‘disease first’ method is an additional method to the generally accepted ‘exposure first’ method. It fills knowledge gaps and prevents new cases of work-related diseases diseases. To let the ‘disease first’ method work we need well-functioning EWS, international collaboration between experts on the identification and evaluation of NERCs, responsible managers, branch organizations and trade unions.
*MODERNET: Monitoring trends in Occupational Diseases and tracing new and Emerging Risks in a NETwork