WORK IN AN OFFSET PRINTING PRESS AND EXPOSURE TO ORGANIC SOLVENTS

Offset printing presses are very busy workplaces. Different solvents are used for cleaning and moisturizing of the machines in such presses.For such purposes, mostly used chemicals are aliphatic hydrocarbons and some more complex solvents consisting of aromatic hydrocarbons. Long time exposure to these chemicals may lead to serious health effects, mainly related to central nervous system. The study was a part of research projects conducted during Masters Programme in Occupational Medicine in Bergen, Norway, 2000-2002.

Introduction:

The study was conducted in an Offset Printing Press in Norway. This offset printing press was a newly established printing press and no measurement of organic solvents has been performed there before. So the main purpose of this study was to document the conditions regarding the solvent exposure in this offset printing press, whether they do comply the Norwegian occupational exposure limit.

This offset printing press consisted of several type of printing machines, which vary from a single colour machine with all manual functions including cleaning (Heidelberg) to brand new four-colour to five-colour machines with automatic cleaning.

The solvents being used for cleaning and moisturizing of the machines in this press have been included in this study. For the purpose of cleaning and moisturizing of the machines were used mostly aliphatic hydrocarbons and some more complex solvents consisting of aromatic hydrocarbons. The list of chemical substances provided by the management revealed the use of Vann wash V120 and G205 for cleaning and Solvent1 for the moisturizing of the machines. All these solutions are mixture of different organic solvents.

Methods:

The study was performed in collaboration with the concerned Occupational Health Service. The measurements consist of three whole day personal exposures at three different printing machines on 12.01.2001, 15.01.2001 and 16.01.2001. For the convenience, workers of the morning shift were included in the study.

On the first two days of measurements, occupational hygienist from the concerned Occupational Health System did all measurements. On the last day of measurements three master students from the Section for occupational medicine, University of Bergen along with their supervisor Dr. Magne Bråtveit performed the measurements. At the beginning of the working shift, all measuring devices were fixed to the concerned study subjects and the time was noted.

The whole day personal measurements were sampled using pumps (no.9001, 9101,9401and 8906) and charcoal tubes (50/100 mg). The pump no. 8906 had the flow rate of 8, where as the rest had the flow rate of 4. All pumps were calibrated differently at the X-Lab and the values were given in the calibration sheet. At the end of shift, the time and other readings were noted and the pumps were switched off. All the samples (charcoal tubes) were analysed at the X-Lab according to the standard procedures. With the help of Gas Chromatography method the contents of the different organic solvents in the samples were noted and calculated using standard formulae.

There were no special inclusion criteria for the workers for study. Each day three workers working at the one of the three main operating machines were included in the study. So the operators of the Heidelberg, Lithrone28 and Lithrone28P were included in the study. The reason for excluding workers from the other part of the office was the potential exposure of these workers to different organic solvents.

The old Heidelberg machine was fully manual operating including cleaning of machine, rubberizing and cleaning of roll. Though other two machines Lithrone 28 and Lithrone 28P were fully automatic including cleaning, there was potential exposure to isopropanol used for continuous moisturizing of the machine. The study included only personal monitoring.

Results:

All samples of personal measurements of the organic solvents collected in three days were analysed by gas chromatography. Only the overall mean value of each solvent detected by the Gas Chromatography was calculated. The values are given in the Table 1.

Table 1:
Organic Solvents Results Norwegian occupational exposure limit
C9 1.715 ppm 25 ppm
C10 0.43 ppm 25 ppm
C11 0.26 ppm 25 ppm
C12 1.159 ppm 25 ppm
1,2,3-TMB(Trimethylbenzene) 2.33 ppm 25 ppm
1,2,4-TMB 0.45 ppm 25 ppm
1,3,5-TMB 0.25 ppm 25 ppm
Isopropanol 35.83 ppm 100 ppm

In the table no. 1, the values of all organic solvents are within the Norwegian occupational exposure limits.

The additive effect of all these organic solvents is calculated as follows:

Additive Factor = C1/T1 + C2/T2 +................+ Cn/Tn

I.E. Additive Factor = 1.715/25 + 0.43/25 + 0.26/25 + 1.159/25 + 2.33/25 +
0.45/25 + 0.25/25 + 35.83/100

= 0.98

The additive effect of all organic solvents is below unity, so the additive effect of all solvents is below the occupational exposure limit. As the study done by us was the first study of that type in that particular offset printing press, no comparison with the previous measurement could be performed.

Discussion:
The result of these measurements shows that the exposure to the organic solvents used in this offset printing press is with in the present Norwegian occupational exposure limits. Similarly, the additive factor is also below unity. It seems that all the solvents used for cleaning and moisturizing of the machines in this press at present give low levels of exposure to solvents.

Survey of the work place revealed the presence of only general exhaust system. Majority of the workers was working without any personal protective equipment. Some of them were using gloves while doing manual cleaning.

In the exposure at this level, there is no likelihood to have any health hazard effect. Nevertheless, the standard of the operation in this press should be maintained in this level with strict engineering and administrative control, follow up measurements and constant workers'' health check up.

Dr. Sunil Kumar Joshi
Occupational and Environmental Medicine Specialist
Asst. Professor of Community Medicine,
Kathmandu Medical College, Sinamangal