Industrial hygiene and safety
Fifteen minutes at 100 dBA use up the entire noise dose of an eight-hour working day. Every additional 3 dB cuts the permitted time in half.
01Two complementary disciplines
Safety at work deals with accidents: sudden events that cause injury, such as a fall, being caught in machinery or an electric shock. Hygiene deals with occupational diseases: harm that sets in slowly through repeated exposure to an agent, such as deafness from noise or lead poisoning from soldering. Both share the goal of anticipating, recognizing, evaluating and controlling risks before they cause harm.
The Italian physician Bernardino Ramazzini published in 1700 the first systematic treatise on the diseases of trades, and proposed asking every patient what work they did. In Argentina, the legal basis is Law 19,587 on Hygiene and Safety at Work and its regulatory decree 351/79, which are covered in the legal framework unit. The presentation for technicians is in health and safety, in the Electronics Technician program.
02Risk agents
| Type | Examples | In electronics |
|---|---|---|
| Physical | Noise, vibration, lighting, heat load, radiation | Radio frequency in antenna tests, lasers, inspection X-rays |
| Chemical | Gases, vapors, fumes, dusts, liquids | Solder flux fumes, lead, cleaning solvents, etching acids |
| Biological | Bacteria, viruses, fungi | Equipment maintenance in hospitals |
| Ergonomic | Postures, repetitive movements, loads | Manual assembly, prolonged work under a microscope |
| Psychosocial | Mental load, shifts, deadline pressure | On-call duty for critical systems |
For each agent, hygiene defines a measurable quantity and a reference value: the concentration in the air for a chemical contaminant, the sound level for noise, the illuminance for light. The evaluation compares the measured exposure with that value.
03Noise: level, dose and equivalent level
Noise is the most widespread physical agent in industry, and the deafness it causes is irreversible. The sound level is measured with A-weighting, in dBA, which imitates the sensitivity of the ear. SRT (Superintendency of Occupational Risks) Resolution 295/03 adopted as its criterion 85 dBA for 8 hours, with a 3 dB exchange rate: for every 3 dB more, which is twice the energy, the permitted time is cut in half:
A working day with three tasks at different sound levels. Each bar is the fraction of the daily dose contributed by one task; the red line is 100%. If the hours add up to more than 8, the last task is adjusted.
04The hierarchy of controls
Once a risk has been evaluated, the measures are chosen in order of decreasing effectiveness. The first ones act on the hazard; the last ones depend on each person doing the right thing every time:
| Level | Measure | Example with noise |
|---|---|---|
| 1 | Elimination | Replace a riveting process with a bonding one |
| 2 | Substitution | A compressor with a lower sound level |
| 3 | Engineering controls | Acoustic enclosure, anti-vibration mounts |
| 4 | Administrative controls | Task rotation to lower the dose, signage |
| 5 | Personal protective equipment | Hearing protectors |
Personal protective equipment is the last resort, not the first: it protects only if it is worn properly and all the time, and it does not reduce the risk for anyone else.
05In the laboratory
Using a sound level meter, measure the sound level at different stations in a workshop and draw up a plan with the values. Estimate the dose received by a person according to their route through the day.
Compare the exposure to flux fumes at a soldering station with and without local extraction, observing the plume with a lamp placed at the side.
Walk through an electronics laboratory and list the risk agents at each station, with the control measure that applies according to the hierarchy.
06Common mistakes
- Adding decibels as plain numbers. Two 85 dBA sources give 88 dBA, not 170.
- Believing that a slightly higher level is only slightly riskier. With a 3 dB exchange rate, 91 dBA allows only 2 hours.
- Starting with hearing protectors. They are the last step of the hierarchy of controls.
- Confusing an accident with an occupational disease. The disease appears years later and is harder to attribute.
07Self-assessment
How much time per day is allowed at 94 dBA?
1 hour: 9 dB above 85 is three halvings.
A person spends 4 hours at 88 dBA and 4 hours at 80 dBA. What dose do they receive?
\( 4/4 + 4/25.4 \approx 1.16 \): 116%, excessive.
What 8-hour equivalent level corresponds to a dose of 200%?
\( 85 + 10\log_{10} 2 = 88 \) dBA.
Why are soldering fumes a chemical agent and not a physical one?
Because the harm is caused by the substances that are inhaled: the flux compounds and the metals.
08Further reading
- International Labour Organization. Encyclopaedia of Occupational Health and Safety. Spanish edition: “Enciclopedia de salud y seguridad en el trabajo”, Ministerio de Trabajo y Asuntos Sociales de España, 2001. The reference work, with chapters by risk agent and by industry.
- Barry S. Levy, David H. Wegman, Sherry L. Baron and Rosemary K. Sokas (eds.). Occupational and Environmental Health. 7th ed., Oxford University Press, 2017. Occupational hygiene from the public health perspective, with exposure assessment.
- Superintendency of Occupational Risks (SRT). Resolutions 295/2003 and 85/2012. Boletín Oficial de la República Argentina (in Spanish). The reference values for physical and chemical agents, and the noise measurement protocol.