Data Useful for Health Identification (MSDS) Threshold Limit Values (TLV) Odor threshold for vapor Physical state Vapor pressure of liquid Sensitivity.

Data Useful for Health Identification (MSDS)

• Threshold Limit Values (TLV)

• Odor threshold for vapor

• Physical state

• Vapor pressure of liquid

• Sensitivity to chemical or impact

• Rates and heats of reaction

• Hazardous by-products

• Reactivity with other chemicals

• LEL and UEL

• Noise level of equipment

• Types and degree of radiation

MSDS at ITRI

http://www.iosh.gov.tw/msds.htm

Evaluation

The evaluation phase determines the extent and degree of employee exposure to toxicants and physical hazards in the workplace environment.

To establish the effectiveness of existing controls, samples are taken to determine the worker’s exposure to conditions that may be harmful.

After obtaining the exposure data, it is necessary to compare them with standards such as TLVs, PELs and IDLHs.

Evaluating Exposures to Volatile Toxicants (1)

For continuous concentration data, the time-weighted average concentration (TWA) is

where C(t) is the measured concentration in ppm or mg/m^3 of the chemical in air and tw is the worker shift time in hours.

wtdttCTWA

0)(

8

1

Evaluating Exposures to Volatile Toxicants (2)

For intermittent samples obtained at fixed points in time

where Ci is the measured concentration value in the ith period of time Ti.

81

n

iiiTC

TWA

Evaluating Exposures to Volatile Toxicants (3)

If more than one chemical is present in the workplace, one approach is to assume that the effects of toxicants are additive. Let

where Ci is the concentration of chemical i; n is the total number of toxicants; (TLV-TWA)i is the TLV-TWA for chemical i. If A exceeds unity, then the workers are over-exposed.

n

i i

i

TWATLV

CA

1 )(

Evaluating Exposures to Volatile Toxicants (4)

The mixture TLV-TWA can be computed by

If the sum of the concentration of the toxicants in the mixture exceeds this amount, then the workers are over-exposed.

n

i i

i

n

ii

mix

TWATLVC

CTWATLV

1

1

)(

)(

Evaluating Exposures to Dusts

• Toxicological theory teaches that dust particles which present the greatest hazard to the lungs are normally in the particle size range of 0.2 to 0.5 microns.

• Dust evaluation calculations are done in an identical manner to volatile vapor.

Noise

• Noise levels are measured in decibels. A decibel is a relative logarithmic scale used to compare the intensity of two sounds.

• For convenience, the hearing threshold is set at 0 dBA. (Table 2-5, Table 2-6)

I

I010log10(dB)Intensity Noise

Evaluating Exposures to Noise

Noise evaluation calculations are performed identically to calculations for vapors except that dBA is used instead of ppm and exposure hours is used instead of TLV-TWA.