INDICE DE TABLAS

The saturated hydrocarbons are used in industry as fuels, lubricants, and solvents. After undergoing processes of alkylation, isomerization, and dehydrogenation, they also act as starting materials for the synthesis of paints, protective coatings, plastics, synthetic rubber, resins, pesticides, synthetic detergents, and a wide variety of petro- chemicals. The fuels, lubricants, and solvents are mixtures that may contain many different hydrocarbons

The array of chemical substances usually termed solvents is many. Solvents are substances that are capable of dissolving or dispersing one or more other sub- stances. Organic solvents are carbon-based solvents—that is, they contain carbon in their molecular structure. Millions and millions of people come in close contact with organic solvents through the use of household and industrial products. The end products include but are not limited to paints, varnishes, lacquers, adhesives, glues, cleaning agents, and products to remove oils, greases, and like substances. Many organic solvents are recognized for their neurotoxicity (e.g., n-hexane, tetrachloro- ethylene, toluene), as carcinogens (i.e., benzene, carbon tetrachloride, trichloroethyl- ene), and as reproductive hazards (e.g., 2-ethoxyethanol, 2-methoxyethanol, methyl chloride). Global industrialization has been very closely associated with the exten- sive use of a large variety of solvents. The numbers and groups of industrial solvents are very large. Industrial solvents have been classified under many names. In brief, these include:

aliphatic hydrocarbons; alicyclic hydrocarbons; alcohols;

glycols and derivatives; ethers and epoxy compounds; esters;

arboxylic acids and anhydrides; aldehydes and ketones;

aliphatic halogenated hydrocarbons; aliphatic amines;

cyanides and nitriles; aromatic hydrocarbons;

phenols and phenolic compounds; aromatic halogenated hydrocarbons; aromatic amines;

Industrial Solvents 33

organic nitrogen compounds; organic chemicals; and halogens.

Each group includes a very large number of chemical substances that have been used extensively in chemical laboratories, multiple industries, and homes. In fact, the list is very large. The following pages provide brief information on the uses, manner of exposure, toxicity, and health effects of some of the solvents. More information on different solvents is available in the literature.1–5,16–18

4.2.1 FlaMMableand CoMbustIble solvents

For purposes of safety, it is necessary that the worker, manager, and related groups managing industrial solvents should know and understand the requirements of the Occupational Safety and Health Administration (OSHA) in the management of safe storage of flammable and combustible liquids. The worker should know the differ- ence between a flammable liquid and a combustible substance. A flammable liquid is one that has a flash point below 100°F (37.8°C), except for any mixture having components with flash points of 100°F (37.8°C) or higher, the total of which make up 99% or more of the mixture) (1910.106(a)(19)). There are three categories of flam- mable liquids:

class 1A: liquids having flashpoints below 73°F (22.8°C) and having boiling points below 100°F (37.8°C) (1910.106(a)(19)(i)) (e.g., acetaldehyde, ethyl ether, and cyclohexane);

class 1B: liquids having flash points below 73°F (22.8°C) and having boiling points at or above 100°F (37.8°C) (1910.106(a)(19)(ii)) (e.g., acetone, ben- zene, and toluene); and

class 1C: liquids having flash points at or above 73°F (22.8°C) and having boiling points below 100°F (37.8°C) (1910.106(a)(19)(iii)) (e.g., hydrazine, styrene, and turpentine).

In contrast, a combustible liquid has a flash point at or above 100°F (37.8°C) (1910.106(a)(18)). The combustible liquids are divided into two classes:

class 2: liquids having flash points at or above 100°F (37.8°C) and below 140°F (60°C), except any mixture having components with flash points of 200°F (93.3°C) or higher, the volume of which makes up 99% or more of the total volume of the mixture (1910.106(a)(18)(i)) (e.g., acetic acid, naphtha, and standard solvent); and

class 3: liquids having flash points at or above 140°F (60°C) (1910.106(a)(18)(ii)). Class 3 liquids are subdivided into two subclasses:

class 3A: liquids having flash points at or above 140°F (60°C) and below 200°F, except any mixture having components with flash points of 200°F (93.3°C)

or higher, the total volume of which makes up 99% or more of the total vol- ume of the mixture (1910.106(a)(18)(ii)(a) (e.g., cyclohexanol, formic acid, and nitrobenzene); and

class 3B: liquids having flash points at or above 200°F (93.3°C) (1910.106(a) (18)(ii)(b)) (e.g., formalin and picric acid).

According to 1910.106(a)(18)(ii)(b), class 3B liquids include those with flash points at or above 200°F (93.3°C). This section does not cover class 3B liquids. Where the term “class 3 liquids” is used in the section, it means only class 3A liq- uids. (Class 3B is used in this document for reference purposes only.)

It should be noted that whenever a combustible liquid is heated for use to within 30°F (16.7°C) of its flash point, it should be handled in accordance with the require- ments for the next lower class of liquids (1910.106(a)(18)(iii)).

The flash point and boiling point determine the class of a liquid. However, these should not be the only criteria used to determine the hazards of a liquid. Many other factors should also be considered for the proper use and storage of hazardous liquids. These factors include ignition temperature, lower explosive limit (LEL) or upper explosive limit (UEL), vapor pressure, specific gravity, and vapor density.

Exposure to solvents and other organic liquids is one of the most common chem- ical health risks at workplaces. Most of the organic solvents are combustible and often highly volatile and extremely flammable; they require care and precaution dur- ing use. Some solvents produce vapors that are heavier than air. These may move on the floor or ground to a distant ignition source, a spark point from welding, or static electricity and result in disaster. Smoking could also cause the vapors to explode. Vapors of solvents are also known to accumulate in confined places and to cause risks to health and the workplace.

4.2.2 usesoF solvents

The most common uses for organic solvents are chemical synthesis, dry cleaning of cloth, paint thinners, removers of nail polish and glue, detergents, and waste spots. Examples of different solvents include but are not restricted to tetra chloroethylene, toluene, turpentine, acetone, ethanol, methyl acetate, and ethyl acetate. Because of the multiple activities and prolonged use of solvents, the hazard to human health has increased extensively. Also, solvents find use in different phases of the electronics industry and primarily as removers of grease, inks, paints, waxes, and glues, as well as in total cleaning processes. There is a wide range of organic solvents, some very toxic and others only mildly toxic. The subgroups should be considered to have a better idea of specific hazard risks and uses. The aromatic compounds and the chlo- rinated hydrocarbons are perhaps the most dangerous groups of solvents because many of them are known to cause cancer and other serious diseases. The organic solvents are widely used in the manufacturing, transportation, and other industrial sectors. These compounds are used in the manufacture of paints, dyes, agricultural products, and many other products. Because organic solvents are ingredients of many products, such as paints and cleaning agents, they are also found in nonmanufactur- ing workplaces and nonwork settings.

Industrial Solvents 35

4.2.3 exposureto solvents

Industrial workers and the general public become exposed to industrial solvents in a variety of ways—for instance, during the fabrication and manufacturing processes of different industrial products. These include but are not limited to products in engineering, textiles, paints, house building and construction, footwear, the food industry, woodworking, rubber, dry cleaning, plastics, manufacture of lacquers and varnishes, adhesives, printing inks and ink removers, pesticides, toiletries, drugs and pharmaceuticals, polymer, dyes and pigments, detergents, soaps and cleaning agents, hospital equipment, and many other associated activities.

Human exposure to a variety of industrial solvents and the subsequent health effects are modulated with the concentration of the solvent (as vapor, mist, or other) in the ambient air, poor ventilation in the workplace, and presence of higher vapor concentration. During prolonged periods of exposure (through inhalation), industrial solvents cause health disorders in workers. Organic solvents are lipid soluble and enter the body rapidly through skin absorption and blood; they cause skin irritation, central nervous system (CNS) depression, and other deleterious effects. High con- centrations of benzene, for instance, are known to cause CNS depression or cardiac arrhythmias and fatal injury. Exposure through skin absorption produces dermatitis, while inhalation of high concentrations leads to bronchial irritation or pulmonary edema. Thus, if or when workers become negligent and do not practice proper safety regulations during handling of industrial solvents, they become the victims and suf- fer chronic health disorders.

Industrial workers and the general public are exposed to solvents through one route or a number of routes simultaneously, depending on the properties of the candidate solvent, the worker’s capability, and duration of use. Most solvents are “volatile”—that is, they evaporate into the air very quickly. The fumes, dusts, gases, and vapors that result can then be breathed in and easily passed through the lungs into the bloodstream. Another route of entry into the body is by ingestion, where fine droplets of solvents enter the body through swallowing. Oral or mouth contact with contaminated hands, food, and cigarettes also leads to the ingestion of solvents. Yet another entry route of solvents to the human body is through skin absorption. Direct skin contact of solvents allows them to enter the bloodstream. Thus, the rapid man- ner of exposure to different industrial solvents in humans is by inhalation (respira- tory), ingestion (oral), and skin (dermal) absorption at workplaces, as well as from a polluted atmosphere. The health effects of solvents on humans are modulated by several factors, for instance:

how easily and quickly a solvent evaporates at the ambient temperature; •

characteristics of the solvent—namely, its solubility in water or fat; •

concentration of the solvent in the air at the work environment; •

nature of work associated with the solvent; and •

duration or exposure period of the worker to the solvent. •

Contamination affecting community water supplies, food additives, or household chemicals is an important source of solvent exposure. Well-water sampling, both in

the United States and abroad, has revealed quantities of chlorinated hydrocarbons and other solvents. As discussed earlier, most of the organic solvents, depending on their volatility, are flammable or highly flammable. However, there are certain exceptions, like chlorinated solvents such as dichloromethane and chloroform. Mix- tures of solvent vapors are very hazardous and can cause explosions. Solvent vapors are heavier than air; they sink to the bottom and can travel long distances. Solvent vapors found in empty drums, containers, and cans often pose hazards of flash fires; hence, empty containers of volatile solvents should be stored in open spaces upside down. For instance, ethers, diethyl ethers, and tetra hydrofuran (THF) form highly explosive organic peroxides on exposure to light and oxygen in the air. Ethers need to be stored in the dark and in closed canisters in the presence of stabilizers such as sodium hydroxide and BHT (butylated hydroxytoluene).

One potential hazard of solvents is flammability. It is therefore very important to take adequate precautions and timely care to contain fires and consequent fire haz- ards. In fact, hazardous liquids need special precautions during storage, handling, and transportation. Industrial workers and managers should be well aware of the rules and regulations of the National Fire Protection Agency (NFPA) and the Inter- national Fire Code Institute (IFCI). These organizations have developed uniform fire codes and guidelines for the safe storage and use of flammable and combustible liquids. These guidelines are not mandatory unless a federal, state, or local authority chooses to use them. In contrast, OSHA has developed mandatory regulations for the general industry (29 CFR 1910.106), construction industry (29 CFR 1926.152), and shipyard industry (29 CFR 1915.36).

4.3 drugS, PharmaCeutiCal ProduCtS,