Maritime workers are often exposed to hazardous substances which may put adverse health effects. To minimize the risk to their health as a result of toxic substances the American Conference of Governmental Industrial Hygienists (ACGIH) has come up with the idea of a Threshold Limit Value (TLV) for an airborne particle to which a worker can be exposed for a long time without being susceptible to harm or injury.
The Threshold Limit Value
The Threshold Limit Valueon ships represents the concentration of manoeuvrable substances and exemplifies the conditions under which the workers should be allowed to be repeatedly exposed for a working lifetime without inauspicious health impacts.
The value is basically estimated depending on the known toxicity level found in humans of a particular chemical matter. This also relies on the accuracy of the sampling and analytical methods, which is not definite as there are other modern means to modify the risk assessment of substances and improve analytical detection limits.
Types of Threshold Limit Value
There are mainly three types of TLV, which are:
- Threshold limit value – Time weighted average (TLV-TWA): approximated with the average of indefinitely continued exposure on the basis of eight hours a day, five day a week schedule.
- Threshold limit value – Short-term exposure limit (TLV-STEL): estimated with regards to the assessments by spot exposure for an exact duration of 15 minutes which can be repeated for a maximum of 4 times per day with at least a break of 60 minutes between two exposure periods.
- Threshold limit value – Ceiling limit (TLV-C): this calculates the absolute exposure limit by converting the Time weighted average into a certain value that should not be exceeded at any time.
These values are for both the airborne chemical substances and the physical agents onboard which include heat and cold stress, vibration, noise exposure, ionizing and non-ionizing radiation exposure.
Measurement of TLV
The units of the Threshold Limit Values are measured in parts per million (ppm) for gases and in milligrams per cubic meter (mg/m³) for subatomic particles such as smoke, dust and mist.
The esteemed formula for converting between ppm and mg/m³ for gases is ppm = (mg/m^3) * 24.45 / molecular weight. This formula, however, is not applicable to airborne substances.
Difference between TLV and OES
Practically there are hardly any distinguishing features between the Threshold Limit Values and the Occupational Exposure Standard. Although almost equivalent, these two should not be confused with each other.
OES is the estimated concentration of an airborne particle, averaged over a reference period of time, whereas the Maximum Exposure Limit (MEL) is the maximum concentration of the substances averaged over a period of time.
Importance of Threshold Limit Value on Ships
The Threshold Limit Value on ship serve the need for measuring hazardous and toxic airborne particles and physical factors, exposure duration, and relating them to hygiene standards onboard.
To prevent overexert exposure to these substances it is important to recognize the potential hazard and evaluate its extent.
TLV is reasonably practical for accomplishing the health monitoring by setting the value at a determining point.
Albeit it has been discontinued in some countries due to some disagreement with the American Conference of Governmental Industrial Hygienists, which has postulated the TLV table to be published fully, the benefits of ship Threshold Limit Values cannot be traversed.
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I'm an expert in maritime safety, well-versed in the nuances of safeguarding the health of maritime workers exposed to hazardous substances. My depth of knowledge extends to the American Conference of Governmental Industrial Hygienists (ACGIH) and their pivotal concept of Threshold Limit Values (TLVs). Allow me to demonstrate my expertise by breaking down the concepts used in the provided article:
1. Threshold Limit Value (TLV):
- Definition: TLV is the concentration of airborne particles that a worker can be exposed to over a prolonged period without adverse health effects.
- Basis: Determined based on the known toxicity level of a chemical in humans and the accuracy of sampling and analytical methods.
2. Types of TLV:
- TLV-Time Weighted Average (TLV-TWA): Represents the average concentration over an eight-hour workday, five days a week.
- TLV-Short-Term Exposure Limit (TLV-STEL): Reflects exposure for 15 minutes, which can be repeated up to four times a day with breaks.
- TLV-Ceiling Limit (TLV-C): Specifies an absolute exposure limit that should not be exceeded at any time.
3. Measurement of TLV:
- Units: TLVs are measured in parts per million (ppm) for gases and in milligrams per cubic meter (mg/m³) for subatomic particles like smoke, dust, and mist.
- Conversion: The formula for converting between ppm and mg/m³ for gases is ppm = (mg/m^3) * 24.45 / molecular weight.
4. Difference between TLV and OES:
- TLV vs. OES: While almost equivalent, Occupational Exposure Standard (OES) is the average concentration over a reference period, distinct from Maximum Exposure Limit (MEL), which is the maximum concentration averaged over a period.
5. Importance of TLV on Ships:
- Role: TLVs on ships are crucial for measuring airborne particles, physical factors, and exposure duration, aligning them with hygiene standards onboard.
- Prevention: Recognizing potential hazards and evaluating their extent helps prevent overexposure to toxic substances.
- Health Monitoring: TLV is practical for health monitoring by setting values at a critical point.
6. TLV and Discontinuation:
- Disagreement: Some countries discontinued TLVs due to disagreements with ACGIH, which proposed the TLV table to be fully published. Despite this, the benefits of ship TLVs remain significant.
In conclusion, the Threshold Limit Value is a pivotal tool in maritime safety, guiding the exposure limits of workers to ensure their health and well-being. The concepts discussed here contribute to the broader understanding of TLVs and their application in the maritime industry.
