Лако-красочные материалы — производство

It is evident that many solvents present considerable health hazards and hence have been subject to restriction through regulation. Even when using solvents of low toxicity, their odor may be undesirable in both the working environment and in the area around manuf­acturing facilities. The common modes of entry of these volatile substances in the body are inhalation, skin contact and ingestion. The toxic effects of solvents depend on the amount of solvent and the exposure time, based on which degree of toxicity is represented, as follows.

Acute toxicity represents the acute damage that may occur under short-term exposure to high solvent doses, which can be particu­larly important in cases of accidental ingestion or spills.

Chronic toxicity represents the chronic damage and sensitization that may occur as a result of the absorption of smaller amounts over a longer period of time. Chronic effects are more dangerous since they are often not detected early enough and may lead to health risks such as cancer.

The risk to human health can be minimized by proper personal safety precautions and the use of protective clothing and equip­ment, such as gloves, goggles, organic vapor masks, or even com­plete air-fed suits with visors for spray application in enclosed areas that are also ventilated to prevent build-up of vapor.

Lethal dosage values (LD50 based on oral administration to rats) of solvents are used to represent their toxicities. Lethal concentration values (LC50) are also being used because, in most cases, solvent poisoning is caused by inhalation of solvent vapor.

Most solvents have a characteristic odor, which may be undesirable in many cases. Human perceptibility and sensitivity to the odor of solvent vapors depends on habituation, which varies from person to person, and therefore, it is impossible to give objective rules for determining when an odor becomes objectionable. As a practical perceptive approach, odor intensity is subdivided into four levels — imperceptible, weakly perceptible, moderately perceptible and highly perceptible. The odor threshold is the vapor concen­tration in a cubic meter of air (in ppm) that is just perceptible.

To eliminate the hazards associated with inhalation, limits of solvent vapor in air have been developed separately by different countries. In Germany, the maximum allowable concentration

(Maximale Arbeitsplatzkonzentration) or MAK value was used, which is the maximum concentration of a substance in the atmos­phere at the workplace that is generally not injurious to the health of the employees and is not regarded as intolerable by the latter, even after repeated and long-term exposure. After the new German Ordinance on Hazardous Substances („Gefahrstoffverordnung/ GefStoffV) came into force in 2005, the maximum workplace con­centration of a substance in the air has been reassessed. The new concept regulates the occupational health limit value (Arbeits — platzgrenzwert (AWG)) and the biological limit value (biologischer Grenzwert (BGW)).

In the United States, the equivalent of the MAK value is the threshold limit value (TLV), which is the concentration of a sub­stance in the air to which virtually all workers can be exposed daily without any harmful effects. This value is subdivided into

TLV-TWA (time-weighted average concentration), TLV-STEL (short­term exposure limit) and TLV-C (ceiling limit).