Occupational Exposure to Ultrafine Particles in Metal Additive Manufacturing: A Qualitative and Quantitative Risk Assessment
Abstract
:1. Introduction
2. Materials and Methods
2.1. Operation Conditions and Materials
2.2. Quantitative Assessment
- A condensation particle counter (CPC), TSI®® Model 3007, to measure particle number concentration, with a particle size range of 10 nm to >1 µm in 1 s time resolution;
- A thermo-hygrometer, TSI®® Model 9545, to measure air velocity, room temperature, and relative humidity;
- A personal air sampling pump (SKC AirChek®® TOUCH) to collect samples for subsequent scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analysis. The samples were collected using mixed cellulose ester (MCE) membrane filters (0.8 μm pore) that met NIOSH specifications for analysis of airborne metals. Additionally, these filters can collect particles with high efficiency, including particles much smaller than their nominal pore size [19].
2.3. Qualitative Assessment
- surface chemistry (points: high = 10; medium = 5; low = 0; unknown = 7.5);
- particle shape (points: tubular/fibrous = 10; anisotropic = 5; compact/spherical = 0; unknown = 7.5);
- particle diameter (points: 1–10 nm = 10; 11–40 nm = 5; >40 nm = 0; unknown = 7.5);
- solubility (points: insoluble = 10; soluble = 5; unknown = 7.5);
- carcinogenicity (points: yes = 6; no = 0; unknown = 4.5);
- reproductive toxicity (points: yes = 6; no = 0; unknown = 4.5);
- mutagenicity (points: yes = 6; no = 0; unknown = 4.5);
- dermal toxicity (points: yes = 6; no = 0; unknown = 4.5);
- asthmagen (points: yes = 6; no = 0; unknown = 4.5).
- occupational exposure limits (OELs) (points: <10 µg/m3 = 10; 10–100 µg/m3 = 5; 101–1000 µg/m3 = 2.5; unknown = 7.5; >1000 µg/m3 = 0);
- carcinogenicity (points: yes = 4; no = 0; unknown = 3);
- reproductive toxicity (points: yes = 4; no = 0; unknown = 3);
- mutagenicity (points: yes = 4; no = 0; unknown = 3);
- dermal toxicity (points: yes = 4; no = 0; unknown = 3);
- asthmagen (points: yes = 4; no = 0; unknown = 3).
- estimated amount of material used (points: >100 mg = 25; 11–100 mg = 12.5; 0–10 mg = 6.25; unknown = 18.75);
- dustiness/mistiness (points: high = 30; medium = 15; low = 7.5; unknown = 22.5);
- number of employees with similar exposure (points: >15 = 15; 11–15 = 10; 6–10 = 5; 1–5 = 0; unknown = 11.25);
- frequency of operation (points: daily = 15; weekly = 10; monthly = 5; >monthly = 0; unknown =11.25);
- duration of operation (points: >4 h = 15; 1–4 h = 10; 30–60 min = 5; <30 min = 0; unknown = 11.25).
3. Results
3.1. Quantitative Assessment Results
3.1.1. On-Site Measurements Results
3.1.2. SEM and EDS Results
3.2. Qualitative Assessment Results
4. Discussion
4.1. Quantitative Assessment
4.2. Qualitative Assessment
4.3. Comparision between Qualitative and Quantitative Assessments
5. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Acknowledgments
Conflicts of Interest
References
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Task 1 | Manual handling of the powder to fill the machine container with raw powder |
Task 2 | Removing and cleaning the final part from the machine after the coating process is completed (inside the machine operating area) |
Task 3 | Removing the remains of the powder and cleaning the powder container |
Assessed Parameters | Background (Before Coating Operations) | Near the Machine Powder Tank | Inside the Chamber (Machine) |
---|---|---|---|
Temperature [°C] | 22.5 | 23.1 | 22.6 |
Relative Humidity [%] | 44.7 | 45.2 | 45.0 |
Air Velocity [m/s] | <0.01 | <0.01 | <0.01 |
Task 1 | Task 2 | Task 3 | Background | |
---|---|---|---|---|
Trial 1—Mean Particle number concentration [particles/cm3] | 16,421.69 | 28,895.80 | 18,279.44 | 13,358.94 |
Trial 2—Mean Particle number concentration [particles/cm3] | 16,716.12 | 37,568.52 | 22,708.98 |
CB Factors | Task 1 | Task 2 | Task 3 |
PM OEL | 20 µg/m3 1 | 20 µg/m3 1 | 20 µg/m3 1 |
PM Carcinogenicity | No | No | No |
PM Reproductive | Yes 2 | Yes 2 | Yes 2 |
PM Mutagenicity | No | No | No |
PM Dermal Toxicity | Yes 3 | Yes 3 | Yes 3 |
PM Asthmagen | Yes 4 | Yes 4 | Yes 4 |
NM Surface Chemistry | unknown | unknown | unknown |
NM Particle Shape | unknown | unknown | unknown |
NM Particle Diameter | unknown | unknown | unknown |
NM Solubility | unknown | unknown | unknown |
NM Carcinogenicity | unknown | unknown | unknown |
NM Reproductive Toxicity | unknown | unknown | unknown |
NM Mutagenicity | unknown | unknown | unknown |
NM Dermal Toxicity | unknown | unknown | unknown |
NM Asthmagen | unknown | unknown | unknown |
Severity Score|Band | 72|High | 72|High | 72|High |
Estimated amount of material used | >100 mg | >100 mg | >100 mg |
Dustiness/mistiness | High | High | High |
Number of employees with similar exposure | 1–5 | 1–5 | 1–5 |
Frequency of operation | Daily | Daily | Daily |
Duration of operation | <30 min | 1–4 h | 30–60 min |
Probability Score|Band | 70|Likely | 80|Probable | 75|Likely |
Overall Risk Level Without Controls | RL 3—Containment | RL 4—Seek Specialist Advice | RL 3—Containment |
CB Factors | Task 1 | Task 2 | Task 3 |
PM OEL | 200 µg/m3 1 | 200 µg/m3 1 | 200 µg/m3 1 |
PM Carcinogenicity | Yes 2 | Yes 2 | Yes 2 |
PM Reproductive | No | No | No |
PM Mutagenicity | No | No | No |
PM Dermal Toxicity | Yes 3 | Yes 3 | Yes 3 |
PM Asthmagen | No | No | No |
NM Surface Chemistry | unknown | unknown | unknown |
NM Particle Shape | unknown | unknown | unknown |
NM Particle Diameter | unknown | unknown | unknown |
NM Solubility | unknown | unknown | unknown |
NM Carcinogenicity | unknown | unknown | unknown |
NM Reproductive Toxicity | unknown | unknown | unknown |
NM Mutagenicity | unknown | unknown | unknown |
NM Dermal Toxicity | unknown | unknown | unknown |
NM Asthmagen | unknown | unknown | unknown |
Severity Score|Band | 63|High | 63|High | 63|High |
Estimated amount of material used | >100 mg | >100 mg | >100 mg |
Dustiness/mistiness | High | High | High |
Number of employees with similar exposure | 1–5 | 1–5 | 1–5 |
Frequency of operation | Daily | Daily | Daily |
Duration of operation | <30 min | 1–4 h | 30–60 min |
Probability Score|Band | 70|Likely | 80|Probable | 75|Likely |
Overall Risk Level Without Controls | RL 3—Containment | RL 4—Seek Specialist Advice | RL 3—Containment |
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Sousa, M.; Arezes, P.; Silva, F. Occupational Exposure to Ultrafine Particles in Metal Additive Manufacturing: A Qualitative and Quantitative Risk Assessment. Int. J. Environ. Res. Public Health 2021, 18, 9788. https://doi.org/10.3390/ijerph18189788
Sousa M, Arezes P, Silva F. Occupational Exposure to Ultrafine Particles in Metal Additive Manufacturing: A Qualitative and Quantitative Risk Assessment. International Journal of Environmental Research and Public Health. 2021; 18(18):9788. https://doi.org/10.3390/ijerph18189788
Chicago/Turabian StyleSousa, Marta, Pedro Arezes, and Francisco Silva. 2021. "Occupational Exposure to Ultrafine Particles in Metal Additive Manufacturing: A Qualitative and Quantitative Risk Assessment" International Journal of Environmental Research and Public Health 18, no. 18: 9788. https://doi.org/10.3390/ijerph18189788