Keywords

1 Core Messages

  • The metal industry employs a significant part of the workforce in industrialized countries mainly in machine construction, car engineering, metal production, and electrotechnical production.

  • There are a huge variety of activities in the metal industry and so are occupational skin exposures.

  • In many jobs, there is a high risk of irritant hand dermatitis due to exposure to mechanical and chemical irritants.

  • Prevalence rates of hand dermatitis in metalworking companies may exceed 20%.

  • In contrast to irritant hand dermatitis, allergic contact dermatitis seems to be less prevalent. Most frequent sensitizations seem to be to metalworking fluid constituents and rarely to metals themselves.

2 Introduction

The metal industry is one of the most important sectors in modern industrial activity. In Germany alone, it comprises more than 81,000 companies with more than 4.0 million workers (Federal statistical office 2008a, b). The biggest branches are machine construction, car engineering, metal production, and electrotechnical production, while the classical steel and noniron metal industry has become of less importance. Metalworking is defined as the process of working with metals to create individual parts, assemblies, or large-scale structures. It evolves forming, cutting, and, joining, containing a range variety of activities. Since metalworking processes are so heterogeneous, the exposure of workers may vary widely depending on the kind of job and of the type of metal industry. Metal workers are exposed to numerous exogenous factors and are more susceptible to the effects of exposure to contact irritants.

3 Metalworking Fluids

Metalworking fluids (MWFs) are complex mixture of chemicals and are used in diverse metalworking activities, for example, to lubricate, cool, and clean and protect machine used in the metal treatment. Two main types of MWF (synthetic cooling fluids, cutting fluids) should be distinguished: water-based MWF with a higher irritating and sensitizing potential and oil-based MWF (synthetic neat oils) with a significantly lower risk of irritation and sensitization (Park et al. 2009). The direct contact to these fluids has a health impact in metal workers. They are daily exposed to direct skin contact and inhalation of the aerosols. Metalworking fluids are most important for irritant hand dermatitis, even though nickel is regarded as the most frequent of all reported metal allergies (Fisher and Adams 1986). The risk of irritant contact dermatitis in metalworkers is closely linked to the contact to MWF exposure. In situations of high MWF exposure, the prevalence of hand dermatitis may reach 30% in the workforce. Since the potential of water-based MWF to induce acute irritation is rather low, the majority of MWF-associated cases of irritant contact dermatitis are of the cumulative or chronic type. Once cumulative irritant contact dermatitis (ICD) is established, healing may be very slow even if contact to irritants is avoided and recurrences are frequent. On the other hand, ICD helps all potential allergens to enter the protective shield of the epidermis resulting in allergic contact dermatitis (ACD), which may be superimposed upon ICD. Exposure by inhalation of MWFs is responsible for different diseases of the respiratory system like asthma, chronic bronchitis, and hypersensivity pneumonitis (Park et al. 2009). Increased risk of certain types of cancer, like breast and prostate cancer, has been also described (Thompson et al. 2005; Agalliu et al. 2005).

4 Other Exposures

Metalworkers in the tool machine industry are the group of workers with the third highest incidence of occupational dermatoses in some countries such as Switzerland. Their annual incidence rate reaches 600 cases per 100,000 person per year, with irritant reactions being the predominant diagnosis (Itschner et al. 1996a). In a population-based study, skin diseases accounted for 27% of all occupational diseases in Finnish, and 20% of all workers in a metalworking plant reported symptoms of contact dermatitis (Suuronen et al. 2007). In an earlier study from Italy, the prevalence was very similar with 18.6% (Papa et al. 2000).

Most frequently, based on the most extensive exposure, the hands are affected by contact dermatitis. While irritant contact dermatitis is mostly limited to the exposed areas, allergic contact dermatitis can spread all over the body (Iliev and Elsner 1997).

Other factors like metal dust, friction, pressure, heat, and humidity also contribute to the irritation of the skin (Hinnen and Elsner 1995).

For example, electroplating is a very specific part of the metal industry in which a specific metal salt is deposited onto a metallic object. The principle metals are nickel, chromium, and copper (Foussereau et al. 1982; Kanerva et al. 1997). Whereas copper is a relatively infrequent allergen, some nickel-sensitive patients also react to chromium or to cobalt. Cobalt exposure may also cause dermal effects such as allergic eczema (Fischer and Rystedt 1983). However, sensitivity to nickel-plated metal seems to be a more important problem for consumers than for manufacturers.

Furthermore, employees working on welding processes are constantly exposed to ultraviolet radiation. One study identified a high incidence of cataracts, keratoconjunctivitis, dermatitis, and erythema in steel industry welders (Zamanian et al. 2015).

5 Conclusions

Exposure toward risk factors for the development of contact dermatitis may vary widely depending on the kind of job and even more on the type of metal industry. Not only the multiplicity of exogenous factors but also the variability in the individual behavior makes the estimation of dermal exposure at work very difficult (Iliev et al. 1997). In all cases, the industrial physician examines the room ventilation and stresses the importance of protective gloves, as well as protective creams. However, also frequent washing of the hands to remove the irritant/allergen seems to be an important risk factor (Itschner et al. 1996b).

Besides metalworking fluids considered to be the most important irritants as well as sensitizers, metalworkers are also exposed to other chemical irritants such as cleaning detergents, solvents, and degreasers (Berndt et al. 2000).

Due to the high irritant and allergen exposure in the metalworking industry, the risk of occupational contact dermatitis is high. As the most relevant irritants and allergens do not vary from those in Chap. 172, “Machinists,” it is referred to that list.