Description of the processes is given. The chemical agents used in the different processes include lead and lead alloys with tin and antimony for type; steel, copper, aluminum, zinc, magnesium, chromium, and brass for plates; mineral acids and salts for etching, carbon black and pigments for inks, organic and petroleum solvents for thinning, oils and greases for ink thickening; polymers, gelatin, and cellulosic esters for photographic films and materials; photographic emulsions; glues, varnishes, resins, and paints.

Many of these substances are toxic, flammable, and potential hazards, and may contaminate the workers' skin, clothing, and surroundings while washing, handling, and during accidental spilling. Carbon black may enter the respiratory system and other parts of the workers' bodies. Excessive noise commonly occurs and can cause permanent hearing damage. Press rooms and other printing plant operations develop noise at 90 decibels (A) levels. Other safety and health hazards are also discussed. (Contract No. 210-77-0120)

This major group includes establishments engaged in printing by one or more common processes, such as letterpress; lithography (including offset), gravure, or screen; and those establishments which perform services for the printing trade, such as bookbinding and platemaking. This major group also includes establishments engaged in publishing newspapers, books, and periodicals, regardless of whether or not they do their own printing. News syndicates are classified in Services, Industry 7383. Establishments primarily engaged in textile printing and finishing fabrics are classified in Major Group 22, and those engaged in printing and stamping on fabric articles are classified in Industry 2396. Establishments that manufacture products that contain incidental printing, such as advertising or instructions, are classified according to the nature of the products for example, as cartons, bags, plastics film, or paper.

Establishments that are primarily engaged in publishing newspapers or in publishing and printing newspapers. These establishments carry on the various operations necessary for issuing newspapers, including the gathering of news and the preparation of editorials and advertisements but may or may not perform their own printing. Commercial printing is frequently carried on by establishments engaged in publishing and printing newspapers, but even though commercial printing may be of major importance, such establishments are included in this industry. Establishments not engaged in publishing newspapers but that print newspapers for publishers are classified in SIC 2759: Commercial Printing, Not Elsewhere Classified. News syndicates are classified in SIC 7383: News Syndicates.

Other establishments are engaged in publishing periodicals or in publishing and printing periodicals. These establishments carry on the various operations necessary for issuing periodicals but may or may not perform their own printing. Establishments not engaged in publishing periodicals but which print periodicals for publishers are classified in commercial printing industries. Another category includes establishments primarily engaged in publishing, or in publishing and printing, books and pamphlets. Establishments primarily engaged in printing or in printing and binding (but not publishing) books and pamphlets are classified in SIC 2732: Book Printing. Book printing includes establishments primarily engaged in printing or in printing and binding books and pamphlets, but not publishing. Here is a brief description of some of the major types of printing done to make magazines, books, and other publications.

Offset printing is an indirect printing method that is widely used for printing on polymer substrates. It is characterized by the fact that selective ink adsorption in the printing process is achieved by the opposite physical-chemical properties of printing and nonprinting areas on the printing plate.

They mainly differ in printing plate construction, ink characteristics, and, most importantly, usage of dampening solutions. In the wet offset printing process, it is inevitable to use a dampening solution to define printing and nonprinting areas on the printing plate. Waterless offset printing is a process that eliminates this. However, both technologies can be successfully used for printing on polymer substrates and offer certain advantages depending on the end use of the final printed product. Printing on polymer materials is influenced by certain, specific requirements that will direct the choice of the offset printing process (wet or waterless), printing plate, inks, etc.

Offset printing has been a market leader for a long time, in terms of the highest speed of printing and quality of printed products. This advantage may be because of the properties of printing elements on the offset plate (oleophilic—ink-friendly) and nonprinting elements (hydrophilic-dampening-fountain solution-friendly) and of the offset printing process itself.

Among the routine applications of radioisotope gauges in the printing and publishing industry is the measurement of the thickness of metal coatings on bi-metallic casts for offset printing, stereotypes and printing plates, and the determination of the thickness of ink and coatings on paper. Experiments have also been made to measure the thickness of ink films on rollers.

In preparing bi-metallic casts for offset printing, a copper cylinder is first plated with a copper layer 100–200 μm thick and then with a layer of chromium 2–4 μm thick. In order to obtain a satisfactory quality of printing, a uniform thickness of chromium is required and a β-backscatter instrument to check the thickness routinely has been developed which uses a 100 mCi 204Tl source and has an accuracy within ±5%. The thickness of electroplated copper on iron lithographic printing plates has been measured using an X-ray fluorescence technique by exciting and measuring the Fe K X-rays, the intensity of which decreases with increasing copper thickness. The exciting source was 3H/Zr bremsstrahlung and a filter of iron foil was used to remove unwanted copper K X-rays which are also excited. With this method coating thicknesses of about 0.002 mm can be measured to an accuracy within ±2% in 3 min. The X-ray fluorescence method has also been used to determine the thickness of ink on paper during an investigation into the ability of different papers to accept print.(1) Using an iron-based ink (Prussian blue) and a 3H/Zr bremsstrahlung source, only the Fe K X-ray is excited appreciably and its intensity is proportional to the ink thickness.

Screen printing as a technique uses a woven mesh to support an ink-blocking stencil. The attached stencil is forming open areas of mesh that transfer ink as a sharp-edged image onto the substrate (PNEAC 1995). A wide range of ink formulations used in screen-printing processes is available, depending on the substrate and the requirements for the printed product. The screen-printing industry uses liquid materials (organic solvents, inks, varnishes, and cleaning agents) that generate numerous hazardous substances of organic origin, especially contaminants from the group of volatile organic compounds (VOCs) (Kiurski et al. 2013c). Isophorone is the most widely used screen-printing ink solvent (comprising 75 % of the total solvent), followed by cyclohexanone, petroleum distillates, butyl acetate, diacetone alcohol, 2-ethoxy ethyl acetate, and xylene isomers. These substances are pollutants in screen printing wastewater and increase the chemical oxygen demand (COD) and biological oxygen demand (BOD) values. A particularly environmentally unfavorable situation is the use of oxidants that can react with other components and thereby provide an organic halide adsorbent in a concentration of 6 mg/L.

Screen press operators are exposed to organic vapors during ink mixing, printing, screen washing, and drying of final products. The major exposure determinant is the proximity of the solvent evaporating surfaces to the workers' breathing zone (Kamyshny et al. 2011).

Pad printing is a printing process, which enables printing on substrates where other printing techniques show limitations or cannot be used at all. This printing technique enables transferring 2D images onto 3D objects. It allows for quality printing on irregular shapes and uneven surfaces, thus lending printers enormous versatility. Pad printing process has three key elements: the printing pad, the printing form, and the printing ink. During printing, an image is transferred from a printing form onto the printing substrate via the pad. The flexibility of this technology enables printing on flat and/or round surfaces, regardless of the type of substrate. Various substrates and products such as plastic, glass, ceramics, wood, medical devices, foods, and so on can be used. The only limitation of the pad printing technology is the image size; usually, largest designed images are made in the size of 50–100 mm.

Some of the occupational health exposures related to solvent-based inks used in pad printing like naphtha, 2-methoxy-1-1-methylethyl acetate, butyl glycol acetate, 4-hydroxy-4-methylpentan-2-one, ethylbenzene, isotridecanol, cyclohexanone, butyl glycol, and xylene isomers.

Offset printing is the most widespread printing process, which relies on the fact that water and oil do not mix and that the printing and non-printing elements are in the same plane. During the printing process, a fountain solution wets the non-image areas on the printing plate, and the printing ink adheres to the image areas (EPA 2015).

Offset printing ink is a very viscous mixture that consists of pigment, binder resin, and additives. The fountain solution usually contains plate preservative agents, wetting agents, isopropyl alcohol (IPA), buffer substances, and anti-microbial additives. Because of its flammability, volatility, and toxicity, the usage of IPA has been of considerable concern. IPA added to the fountain solution evaporates into the ambient air and contributes to the release of pollutants from the group of volatile organic compounds (Svendsen and Rognes 2010; Kiurski et al. 2013a). Further, VOCs can contribute to the formation of new oxidation products and secondary aerosols that can cause sensory irritation symptoms (Dhada et al. 2015). Odorous emissions are released during the heating and cooling of the varnish.

Aluminum printing plates are widely used in offset printing, and therefore, aluminum is the most common pollutant. Its presence may cause an increase in pH values of wastewater. However, a larger problem may occur after discharges of spent photochemical baths during the manual platemaking (Kiurski 2010).

Lithographic printing was invented by Alois Senefelder at the end of the eighteenth century, with a stone as a printing form, which is the base of today's well-known offset printing. Since then, this printing technique has rapidly grown over the past decades. Although today's offset uses a metal-based printing plate as a form for printing, some of the physical-chemical properties are responsible for the quality of printing. The word offset comes from the phrase set-off, which symbolically shows the way of getting the printed sample on the substrate (e.g., paper)—indirectly from a rubber blanket. Printed images are previously directly transferred from the printing plate to a rubber blanket (Figure 1).

Figure 1 - Components of the basic principle—offset printing unit.
Source: Quality of Printing, Science Direct
https://www.sciencedirect.com/topics/engineering/quality-of-printing

Lithographic offset printing is a widely used printing technique in which the image on a printing plate is printed on a rubber cylinder and then transferred to the printing material. The rubber cylinder gives great flexibility, clarity of image, and speed when compared with other printing techniques. The term "offset lithography" was coined to describe the process by which an image is transferred from a lithographic plate onto a rubber blanket cylinder and then pressed from the cylinder onto paper or other substrates. About 50 percent of all the printing done in the United States is lithographic.

Flexographic printing is a common printing method in the packaging field. The printing method is characterized primarily on the flexible rubber relief printing plate and the low viscosity inks that make it suitable for use on almost any substrate, and the formulation of the inks depends on the process and printed matter. Generally, the solvent-based and water-borne inks are dried by solvent evaporation, or they are absorbed in the substrate. The basic elements in flexographic inks are colorants, binders, and solvents (Johnson 2008). Health hazards associated with solvent based inks used in flexographic printing include ethyl alcohol, ethoxypropanol, methoxypropanol, ethyl acetate, methyl ethyl ketone, methoxypropyl acetate, and isopropyl acetate.

Three basic types of materials used in flexographic printing plate production are rubber plates, liquid photopolymer media, and solid-sheet photopolymers. The major components in the photo-sensitive layer are binders, monomers, and photo-initiators. The washout solvents are frequently chlorinated solvents, such as perchloroethylene (Andrade et al. 2012). Because of the environmental hazards of chlorinated solvents, substitutes are being sought. A negative feature of the rinse solution is its organic origin, and, if it reaches the aquifer, it will consume oxygen and make it scarce. Additionally, it increases the COD and BOD values of wastewaters (Kiurski 2010).

Gravure printing is a form of intaglio printing. "Intaglio" comes from an Italian word meaning "to engrave;" the word "gravure" is taken from the French and has the same meaning. Intaglio printing methods were developed by carving or engraving an image in stone or metal. In contemporary commercial gravure printing, a reversed image is cut into a thick metal plate wrapped around a cylinder. Ink, applied to the plate and wiped off the surface with a blade, remains in the incised image cells so that when the paper is placed against the plate it absorbs the ink and produces a crisp copy of the image. Gravure is also used for packaging designs, such as the printed plastic wrapping around many perishable foods or around beverage containers. Fifteen percent of the gravure's printing market in the late 1990s was devoted to printing labels and wrappers.

Reports indicate the presence of irritant dermatitis and other skin conditions in employees in the printing and publishing industry; this is linked to the frequent use of solvents as well as exposure to printing ink mist, diesel oil, and paper dust. Employees also reported pulmonary symptoms such as chronic bronchitis. Here is an overview of the printing, publishing, and allied industries.

Figure 2 – Rotogravure printing and laminating
Source: Quality Roto Packaging Pvt. Ltd.

Digital printing refers to methods of printing from a digital-based image directly to a variety of media. The application of digital printing has increased recently, because this technique offers a variety of benefits, such as speed, flexibility, cleanliness, competitiveness, and eco-friendliness (Zori and Soleimani-Gorgani 2012). Inks for digital printing are usually classified into two categories, dye and pigment inks. Pigmented inks dry more slowly than dyes, but they are more suitable for printing on matt or plain paper surfaces, producing sharper details and deeper colors (Zhang et al. 2012).

Water-based inks contain 30–80 % water. From the standpoint of environmental protection, given that the water content is up to 80 %, the harmful indoor emissions are minimal. The waste ink cannot be discharged directly into the recipient due to the presence of dyes and other ingredients. Thus, ink manufacturers recommend disposing of their water-based inks as hazardous waste. (Karanikas, et al. 2013).

Bookbinding falls into several categories: edition (large runs), job binding (short runs), library, pamphlet, manifold (business forms or ledgers), and blank book binding. Highly specialized preservation bookbinders usually attempt to restore the original bindings of old books. Bookbinders are generally also involved in post-press work, including collating, perforating, folding, gluing, die-cutting, stamping, and other operations. These peripheral activities generated about $550.1 million in revenues for bookbinders in 1997.

Some of the other related operations include establishments primarily engaged in typesetting for the trade, including advertising typesetting, hand or machine composition, photocomposition, phototypesetting, computer-controlled typesetting, and typographic composition. Other establishments primarily engaged in making plates for printing purposes and in related services. Also included are establishments primarily engaged in making positives or negatives from which offset lithographic plates are made.

Printing inks are mixtures of three main types of ingredients: pigments, vehicles, and additives. Pigments used in printing inks include both inorganic pigments such as carbon black and titanium dioxide and organic pigments, which are frequently dyes rendered insoluble by complexing with a metal ion. Most organic pigments are prepared from azo, anthraquinone and triarylmethane dyes, and phthalocyanines.

There five main printing processes are discussed above, and inks are designed for the specific process. Lithography and letterpress are collectively known as the 'paste ink' processes and use inks that are essentially non-volatile at normal temperatures. Flexography and gravure are known as the 'liquid ink' processes and are based upon volatile solvents that evaporate readily at room temperatures. Screen printing uses inks that fall between the other two groups.

The choice of the vehicle (solvent with resins) for a printing ink depends on the printing process, how the ink will be dried, and the substrate on which the image is to be printed. In lithography and letterpress, where inks are dried by absorption and oxidation, vehicles are generally mixtures of mineral and vegetable oils and resins. Flexographic inks, which are designed to dry quickly by evaporation, can be either water-based or based on organic solvents (such as ethanol, ethyl acetate, n-propanol, or isopropanol) with a wide variety of resins. Vehicles for gravure inks, which are also dry by evaporation, may also contain aromatic or aliphatic hydrocarbons and ketones as solvents. Inks for screen printing use organic solvents that are somewhat less volatile than those used for flexography or gravure (higher glycol ethers and aromatic and aliphatic hydrocarbons). Additives in inks include driers, waxes, and plasticizers.

The manufacture of inks consists of dissolving or dispersing resins in organic solvents or oils to produce the vehicle (varnish), mixing and dispersing the pigment or dye into the vehicle, the introduction of any additives, and packaging. Some or all of these stages may be done manually or automatically in a batch process or as a continuous process.

During the manufacture of printing inks, exposure to pigments, vehicles, and additives can occur through inhalation or skin contact during mixing and dispersion and during the clean-up of mixers. Exposures are higher with liquid inks than with paste inks. During newspaper printing by letterpress or lithography, the major exposure is to ink mist. Rotary letterpress was the dominant process for the production of newspapers until the 1970s. It has now been largely replaced by web offset lithograph, in which exposures to ink mist are considerably lower than for letterpress. In other lithographic and letterpress printing, the major exposure is to hydrocarbon-based cleaning solvents and isopropanol from damping solutions. In flexographic, gravure, and screen printing, exposures are mainly to organic solvents. Historically, some workers in both ink manufacture and printing were exposed to much higher levels of lead, polycyclic aromatic hydrocarbons, and benzene than today, and the development and use of modern control technologies have made possible the marked reduction in solvent and ink mist exposures.

A large volume of epidemiological data deals with potential cancer risks in printing processes. Because of the presence of a fairly large number of adequate cohort and case-control studies, it was considered that there was no marginal benefit in considering further the descriptive studies based on simple tabulations of death certificate causes of death and mentions of occupation. In any case, these latter studies did not provide clear patterns of results.

The evaluation of results of case-control and cohort studies, in particular those regarding relatively rare neoplasms, was hampered by the possibility of reporting or publication bias. A second problem was the poor specificity of exposure information. While most studies were based on crude designations of the exposure variable, a few, most notably some of the cohort studies, did describe risks for subgroups of the printing industry that are more homogenous in exposure circumstances. The International Agency for Research on Cancer (IARC) Working Group tried to identify such subgroup studies with presumably more well-defined common exposure circumstances. In a small number of studies, there was an explicit attempt to identify a group of workers exposed to printing inks. This, like the designation of exposure on the basis of the job or industry title, is of poor specificity. Further, most of these were in the context of community-based case-control studies, and the attribution of exposure was based on job-exposure matrices, which do not discriminate among subsectors of the printing industry.

A third problem was that most of the cohort and record-linkage studies had no information on some important confounders, notably cigarette smoking. It has previously been shown that confounding by smoking is unlikely to distort the relative risk estimate between occupation titles and lung cancer by more than 30%. For other sites that are affected by smoking, the maximal bias is likely to be even lower. The Working Group considered these possible biases when interpreting results. Apart from cancers of the lung, oropharynx, urinary bladder, and kidney, and leukemia, the IARC Working Group considered that the findings are not strong or consistent enough to be evaluated. Here is a link to more detailed health and cancer information from the Working Group: http://www.inchem.org/documents/iarc/vol65/printing.html

Washout solvents are the cleaning and maintenance of printing machines are important for quality printing production, but the health risks of employees must not be forgotten. Most cleaning solutions are obtained from petroleum, a highly volatile and flammable substance. These substances represent health and safety risks in the working environment (flammability) (Kiurski 2010). In the atmosphere, they participate in chemical reactions producing the group of photo-oxidants and lead to smog formation. However, the observed properties are not in accordance with good technological conditions (Bernd Schwegmann GmbH & Co 2015). Conventional detergents are mixtures of hydrocarbons with an ignition temperature of 55 C. This is the lowest temperature at which the steam is developed to such an extent that a spark can be created above the liquid, yielding a combustible mixture.

Other potential health effects of chemicals used in printing include:

Solvents and inks can irritate the skin leading to dermatitis
Some products can cause skin allergy and asthma (e.g. UV inks, laminating adhesives)
Some solvent vapors can make you dizzy, drowsy and affect the central nervous system
Some solvents can damage internal organs (e.g. liver /kidney) if exposure is over a long period
Corrosive acids and alkalis cause skin burns and eye damage (e.g. plate developers)
Some inks cured by UV can cause cancer and harm to the unborn child (Products supplied in Europe by members of the British Coatings Federation (BCF) and/or European Printing Ink Association (EuPIA) should not fall into this category)

More information can be found at: https://www.hse.gov.uk/printing/coshhessentials/printing-process-chemicals.pdf

Note: The following table represents only the potential occupational health concerns related to the entire paper and allied products industries based on a job task or work activity, and any related OSHA standards for regulatory compliance. The information presented does not indicate or suggest a relative risk of exposure based on the location within the table nor provides any exposure information. Health risks associated with fatigue, working long hours, and other psychosocial disorders are not addressed.

The focus of this information is to provide guidance to understand the occupational health hazards from chemical substances, physical and biological agents, radiological, ergonomic, and environmental hazards from exposure to plants and animals. Potential occupational health exposures in this industry were derived from the OSHA Integrated Management Information System database between 1984 to 2020. Additional information was obtained from the National Institute for Occupational Safety and Health (NIOSH) Health Hazard Evaluations performed by request of employee representatives and organizations from 1978 to 2020.

Photos courtesy of Getty Images.