Species-specific inhalable exposures in the nickel industry: A new approach for deriving inhalation occupational exposure limits

Exposure, assessment and health hazards of particulate matter in metal additive manufacturing: A review

Metal additive manufacturing (AM), also known as metal three-dimensional (3D) printing, is a new technology offering design freedom to create complex structures that has found increasing applications in industrial processes. However, due to the fine metal powders and high temperatures involved, the printing process is likely to generate particulate matter (PM) that has a detrimental impact on the environment and human health. Therefore, comprehensive assessement of the exposure and health hazards of PM pollution related to this technique is urgently required. This review provides general knowledge of metal AM and its possible particle release. The health issues of metal PM are described considering the exposure routes, adverse human health outcomes and influencing factors. Methods of evaluating PM exposure and risk assessment techniques are also summarized. Lastly, future research needs are suggested. The information and knowledge presented in this review will contribute to the understanding, assessment, and control of possible risks in metal AM and benefit the wider metal 3D printing community, which includes machine operators, consumers, R&D scientists, and policymakers.

Particle size and metal composition of gouging and lancing fumes

Metal gouging and lancing liberate particles of an unknown size and composition. Fumes are formed when vaporized materials condense in air, creating fine and ultrafine particles which can agglomerate. Particle sizes may be <1 µm in diameter. Inhalation of this mixture of metal fumes can lead to adverse health effects. This study characterized fumes by particle size fractions and metal composition. As particles may be in the submicron range, the nano-size fraction was included. Randomized, side-by-side area samples of fumes liberated during gouging and lancing were collected. Samplers included the conductive plastic Institute of Occupational Medicine (IOM) samplers (inhalable fraction), GK2.69 stainless steel thoracic cyclones (thoracic fraction), aluminum respirable cyclones (respirable fraction), Nanoparticle Respiratory Deposition (NRD) samplers (nano-size fraction), and open-face filter cassettes (particle size distribution-PSD). Samplers were mounted at a height of between 1.3 m and 1.7 m, in the worst-case scenario area (down-wind). Forty-six samples were collected during gouging and 26 during lancing. Mass concentrations per fraction ranges (excluding nano-size) were found to be 1.27-17.27 mg/m³ (inhalable), 1.83-13.96 mg/m³ (thoracic) and 0.88-15.82 mg/m³ (respirable) for gouging; and 2.34-5.60 mg/m³ (inhalable), 2.82-4.01 mg/m³ (thoracic), and 1.89-3.24 mg/m³ (respirable) for lancing. PSD analysis confirmed the presence of nano-size particles with a mean size of 171.76 (±56.27) nm during gouging and 32.33 (±7.17) nm during lancing. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis of samples indicated the presence of chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), nickel (Ni), and tin (Sn) in the respective particle size fractions (including nano-size) of both processes. Negative health effects associated with metal inhalation are well known, while nanoparticles' unique properties enable them to cause further detrimental health effects. The nano-size fraction should be included in personal exposure assessments and control measures.

Development of a New Sequential Extraction Procedure of Nickel Species on Workplace Airborne Particulate Matter: Assessing the Occupational Exposure to Carcinogenic Metal Species

Nickel (Ni) compounds and metallic Ni have many industrial and commercial applications, including their use in the manufacturing of stainless steel. Due to the specific toxicological properties of the different Ni species, there is a growing interest about the availability of analytical methods that allow specific risk assessment, particularly related to exposure to the Ni species classified as carcinogenic. In this paper, we described a speciation method of inorganic Ni compounds in airborne particulate matter, based on selective sequential extractions. The analytical method described in this paper allows the determination of soluble, sulfidic, metallic, and oxide Ni by a simple sequential extraction procedure and determination by Atomic Absorption Spectroscopy using small volumes of solutions and without long evaporation phases. The method has been initially set up on standard laboratory mixtures of known concentrations of different Ni salts. Then it has then been tested on airborne particulate matter (powder and filters) collected in different workstations of a large stainless steel production facility. The method has occurred effectively in the comparison of the obtained results with occupational exposure limit values set by the main international scientific and regulatory agencies for occupational safety and health, in order to prevent both toxic and carcinogenic effects in humans.

Lipid peroxidation and its toxicological implications

Lipid peroxidation is a free radical oxidation of polyunsaturated fatty acids such as linoleic acid or arachidonic acid. This process has been related with various pathologies and disease status mainly because of the oxidation products formed during the process. The oxidation products include reactive aldehydes such as malondialdehyde and 4-hydroxynonenal. These reactive aldehydes can form adducts with DNAs and proteins, leading to the alterations in their functions to cause various diseases. This review will provide a short summary on the implication of lipid peroxidation on cancer, atherosclerosis, and neurodegeneration as well as chemical and biochemical mechanisms by which these adducts affect the pathological conditions. In addition, select examples will be presented where antioxidants were used to counteract oxidative damage caused by lipid peroxidation. At the end, isoprostanes are discussed as a gold standard for the assessment of oxidative damages.

The use of low-cost adsorbents for wastewater purification in mining industries

Recently, great attention has been paid to the environmental problems in mining industry. At present there are different ways of mineral processing, as well as various methods of wastewater treatment, most of them are expensive. Work is ongoing to find low-cost treatments. In this article, low-cost adsorbents, potentially useful for wastewater treatment on mining and metallurgical plants, are reviewed; their characteristics, advantages, and disadvantages of their application are compared. Also adsorption of different metals and radioactive compounds from acidic environment similar to composition of mining and metallurgical wastewaters is considered.

Assessment of fine particulate matter and gaseous pollutants in workplace atmosphere of metallic industry

In the present study, we measured the concentrations of fine particulate matter (PM(2.5)), carbon dioxide (CO(2)), carbon monoxide (CO) and volatile organic carbon (VOC) in the indoor air of the manufacturing department of a metal factory. The daily average PM(2.5) concentration ranged between 86.3 and 404.9 μg/m(3). The isolation of the manufacturing machines reduced. PM(2.5) concentration between 2.5 and 8.8 fold. At the seven measurement points, daily concentrations ranged from 576.7 to 623.4 ppm for CO(2), 0.8 to 15.8 ppm for CO, and 0 to 0.58 ppm for VOC, respectively.

Inhalation exposure to nickel hydroxide nanoparticles induces systemic acute phase response in mice

It has been proposed that acute phase response can be a mechanism by which inhaled particles exert adverse effects on the cardiovascular system. Although some of the human acute phase proteins have been widely studied as biomarkers of systemic inflammation or cardiovascular diseases, there are only a few studies that investigated the role of serum amyloid P (SAP) , a major acute phase protein in mice. In this study, we investigated the changes in SAP, following inhalation exposure to nickel hydroxide nanoparticles (nano-NH) . We conducted 1) acute (4 h) exposure to nano-NH at 100, 500, and 1000 μg/m³ and 2) sub-acute (4h/d for 3d) exposure at 1000 μg/m³, then measured serum SAP protein levels along with hepatic Sap mRNA levels. The results show that inhaled nano-NH can induce systemic acute phase response indicated by increased serum SAP levels and hepatic Sap mRNA levels. To the best of our knowledge, this is the first study showing induction of SAP in response to repeated particle exposure, and the results suggest that SAP can be used as a biomarker for systemic inflammation induced by inhaled particles.

Long-term inhalation exposure to nickel nanoparticles exacerbated atherosclerosis in a susceptible mouse model

BACKGROUND

Because associations have been reported between inhaled ambient ultrafine particles and increased risk of cardiopulmonary disease, it has been suggested that inhaled engineered nanoparticles (NPs) may also induce adverse effects on the cardiovascular system.

OBJECTIVE

We examined the long-term cardiovascular effects of inhaled nickel hydroxide NPs (nano-NH) using a sensitive mouse model.

METHODS

Hyperlipidemic, apoprotein E-deficient (ApoE-/-) mice were exposed to nano-NH at either 0 or 79 μg Ni/m3, via a whole-body inhalation system, for 5 hr/day, 5 days/week, for either 1 week or 5 months. We measured various indicators of oxidative stress and inflammation in the lung and cardiovascular tissue, and we determined plaque formation on the ascending aorta.

RESULTS

Inhaled nano-NH induced significant oxidative stress and inflammation in the pulmonary and extrapulmonary organs, indicated by up-regulated mRNA levels of certain antioxidant enzyme and inflammatory cytokine genes; increased mitochondrial DNA damage in the aorta; significant signs of inflammation in bronchoalveolar lavage fluid; changes in lung histopathology; and induction of acute-phase response. In addition, after 5-month exposures, nano-NH exacerbated the progression of atherosclerosis in ApoE-/- mice.

CONCLUSIONS

This is the first study to report long-term cardiovascular toxicity of an inhaled nanomaterial. Our results clearly demonstrate that long-term exposure to inhaled nano-NH can induce oxidative stress and inflammation, not only in the lung but also in the cardiovascular system, and that this stress and inflammation can ultimately contribute to progression of atherosclerosis in ApoE-/- mice.

Evidence of carcinogenicity in humans of water-soluble nickel salts

BACKGROUND

Increased risks of nasal cancer and lung cancer in nickel refiners have been investigated scientifically and discussed since they were detected in the 1930s. Nickel compounds are considered to be the main cause of the cancer excess. Parts of the nickel producing industry and their consultants oppose the classification of water-soluble nickel salts as human carcinogens, and argue that the risk in exposed workers should be ascribed to other occupational exposures and smoking.

DISCUSSION

Respiratory cancer risks in Welsh, Finnish, and Norwegian nickel refiners add to the evidence of carcinogenicity of water-soluble nickel. In Norwegian refiners, the first epidemiological study in 1973 identified high risks of lung cancer and nasal cancer among long-term electrolysis workers. Risk analyses based on exposure estimates developed in the 1980s supported the view that water-soluble nickel compounds were central in the development of cancer. Recently, new exposure estimates were worked out for the same cohort based on personal monitoring of total nickel and chemical determination of four forms of nickel. Additional data have been collected on life-time smoking habits, and on exposure to arsenic, asbestos, sulphuric acid mists, cobalt, and occupational lung carcinogens outside the refinery. After adjustment for these potential confounding exposures in case-control analyses, the risk pattern added to the evidence of an important role of water-soluble nickel compounds as causes of lung cancer. These Norwegian cancer studies rely on national Cancer Registry data, considered close to complete from 1953 onwards; and on National Population Register data continuously updated with mortality and emigration. Canadian mortality studies--perceived to offer the strongest support to the industry position not to recognise carcinogenicity of water-soluble nickel--appear to suffer from limitations in follow-up time, loss to follow-up, absence of risk analysis with individual exposure estimates, no confounder control, and a likely underestimation of cancer mortality.

CONCLUSIONS

Rejection to recognise water-soluble nickel as a human carcinogen seems to contradict material epidemiological evidence that demonstrates a strong association between water-soluble nickel compounds and risks of lung cancer and nasal cancer. Independent international scientific bodies have classified nickel compounds as carcinogenic to humans, inclusive of water-soluble nickel.

Carcinogenicity assessment of water-soluble nickel compounds

IARC is reassessing the human carcinogenicity of nickel compounds in 2009. To address the inconsistencies among results from studies of water-soluble nickel compounds, we conducted a weight-of-evidence analysis of the relevant epidemiological, toxicological, and carcinogenic mode-of-action data. We found the epidemiological evidence to be limited, in that some, but not all, data suggest that exposure to soluble nickel compounds leads to increased cancer risk in the presence of certain forms of insoluble nickel. Although there is no evidence that soluble nickel acts as a complete carcinogen in animals, there is limited evidence that suggests it may act as a tumor promoter. The mode-of-action data suggest that soluble nickel compounds will not be able to cause genotoxic effects in vivo because they cannot deliver sufficient nickel ions to nuclear sites of target cells. Although the mode-of-action data suggest several possible non-genotoxic effects of the nickel ion, it is unclear whether soluble nickel compounds can elicit these effects in vivo or whether these effects, if elicited, would result in tumor promotion. The mode-of-action data equally support soluble nickel as a promoter or as not being a causal factor in carcinogenesis at all. The weight of evidence does not indicate that soluble nickel compounds are complete carcinogens, and there is only limited evidence that they could act as tumor promoters.

A review of effects of particulate matter-associated nickel and vanadium species on cardiovascular and respiratory systems

Many epidemiological investigations indicate that excess risks of mortality and morbidity may vary among specific PM(2.5) components. Nickel (Ni) and vanadium (V) particulate metal species may potentially be related to increasing respiratory and cardiovascular mortality and morbidity. This review focuses on exposure concentrations of these two species in various settings, their health effects based on epidemiological and toxicological studies and the underlying mechanisms. The evidence shows that environmental exposure concentrations of Ni and V in general setting are lower than the World Health Organization standard (V, 1 microg/m(3)/day) in 2000, or the European Environment Agency standard (Ni, 1 microg/m(3)/day) in 2003, but their associations with cardiopulmonary diseases can still be found. The toxicological mechanism can be explained by laboratory-based studies. Updated safe guidelines on environmental and human exposure of Ni and V are necessary in order to clarify the associations between them and cardiopulmonary diseases and provide environmental intervention policies.