Biomarkers of exposure

Biological monitoring provides an insight into the exposure received by workers from all routes, including inhalation and skin contact. However, to obtain an insight into the relative contributions from these routes of exposure, it is necessary to have some data on inhalation exposure levels and dermal exposure levels. Biological monitoring can also provide information about the effectiveness of personal protective equipment.

Biomonitoring studies generally use one or two analytes to act as markers of exposure to the complex mixture of substances that make up the paint.

1.5.1 Benzene, toluene and xylene

In Poland, phenol and hippuric acids were measured in 51 urine samples from shipyard painters working in small spaces within the ship superstructure and in large holds. The average values of phenol in urine were 12.4–66.4 mg/L compared to 7.9 mg/L on average for a control group. Urinary phenol was attributed to benzene: the benzene concentration in air ranged from undetectable to 11 ppm (35 mg/m³). The average concentrations of hippuric acids in urine (sum of hippuric and methyl hippuric acids) were in the range of 1812–

5500 mg/L compared to 790 mg/L in a control group. Concentrations of toluene and xylene in air were 7 to 88 ppm (26–332 mg/m³) and 23–538 ppm (100–2335 mg/m³), respectively (Mikulski et al., 1972). Elevated values of hippuric acid (up to 6700 mg/L) and methyl hippuric acid (up to 7100 mg/L) were also measured in the urine of shipyard workers in Japan (Ogata et al., 1971).

OCCUPATIONAL EXPOSURE AS A PAINTER 151 Several biomonitoring studies among painters have focused on exposure to toluene.

Apostoli et al. (1982) measured the exposure of 20 workers employed in painting and hand-finishing in an art furniture factory. Inhalation exposure concentrations of toluene were in the range of 10–200 mg/m³. Alveolar toluene concentrations were significantly correlated with environmental toluene concentrations (r = 0.62). Duydu et al. (1999) studied furniture workers involved with painting. They measured urinary hippuric acid and compared the data with inhalation exposure levels. The 8h-TWA air toluene concentration in the two painting areas were 44 and 66 ppm, and the corresponding urinary hippuric acid concentrations were 0.79 and 1.1 g/g creatinine.

Katsuyama et al. (1998) studied the exposure of shipyard painters to toluene and xylene while working in very confined spaces. Air concentrations were high in six of the 14 workplaces where monitoring was undertaken, i.e. the exposure to the total mixture of solvents in air exceeded the combined occupational exposure limit. Urinary excretion of hippuric acid and methyl hippuric acid in the highly exposed painters varied at the end of the shift from 0.07 to 0.92 (geometric mean, 0.22) g/g creatinine and from 0.02 to 0.42 (geometric mean, 0.11) g/g creatinine, respectively. Based on the study by Loizou et al.

(1999), exposure to 50 ppm xylene would be expected to result in the excretion of about 1.25 g/g creatinine of methyl hippuric acid at the end of the exposure period. Concentrations of toluene and xylene in the end-of-exhale air varied from <0.1 to 5.0 ppm and <0.1 to 10.6 ppm, respectively. The biological monitoring data were lower than that expected from inhaling the high concentrations prevalent in these workplaces, which was because the workers wore either a chemical cartridge respirator or a “body-mounted gas mask”

(breathing apparatus).

Krämer et al. (1999) measured exposure levels to inhaled xylene plus concentrations of blood xylene and urinary methyl hippuric acid in a group of paint manufacturers and a group of paint sprayers. Average xylene air concentrations for sprayers were 8 ppm (3 to 21 ppm) and the corresponding average concentrations of xylenes in blood were 130 μg/L (49 to 308 μg/L). They also excreted on average 485 mg/L (range 65–1633 mg/L) methyl hippuric acid in their urine.

1.5.2 Isocyanates

Several researchers have used biological monitoring to evaluate exposure to isocyanates from spray painting. Williams et al. (1999) developed a method for measuring HDI in the urine of exposed workers, based on an analysis of hexamethylene diamine by gas chromatography-mass spectrometry (GC-MS). They measured exposure in 22 workers associated with paint spraying in automobile repair: 11 sprayers who wore respiratory protection, three bystanders and eight unexposed people. Hexamethylene diamine was detected in four sprayers and one bystander. No hexamethylene diamine was detected in the urine of the unexposed subjects. The detectable levels were in the range of 1 to 12 μmol/mol creatinine.

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Pronk et al. (2006b) also analysed urinary hexamethylene diamine levels in autobody workshop workers and industrial painters. A total of 36% of the autobody workshop workers and 10% of the industrial painters had detectable levels of hexamethylene diamine in their urine. Positive samples were found in all groups of workers present in the autobody workshops, including welders, bystanders and office workers. Workers spraying paint wore respiratory protection but less consistently wore gloves (40% in autobody repair shops and 75% in industrial painting companies). For the autobody workshop workers, wearing gloves significantly decreased the odds ratio for having a urine sample positive for hexamethylene diamine (OR, 0.22; 95% CI: 0.09–0.57).

Creely et al. (2006b) measured inhalation exposure and all urinary isocyanate metabolites (methylenedianiline; 2,4-toluene diamine; 2,6-toluene diamine; 1,6-hexamethylene diamine; and isophorone diamine) in a wide range of work situations, including spray painting and roller application of paints. Overall, the geometric mean total isocyanate metabolite level for the data set was 0.29 mmol/mol creatinine (range 0.05–12.64 mmol/mol creatinine). Hexamethylene diamine was the most commonly detected metabolite in the urine samples. The geometric mean total isocyanate metabolite level for roller painting was 0.39 mmol/mol creatinine, and for spray painting, 0.29 mmol/mol creatinine. Inhalation exposure concentrations were low (geometric mean of 1 μg/m³ for both painting operations), and the spray painting workers wore respiratory protection and gloves. The authors suggested that dermal exposure, and possibly ingestion, were important contributors to total exposure.

1.5.3 Other solvents

Kawai et al. (2003) investigated unmetabolized methyl isobutyl ketone and methyl ethyl ketone in the urine of workers in a furniture factory where spray painting and gluing were performed. The correlation between inhalation exposure concentration and the concentration of the corresponding solvent in the end-of-shift urine sample was significant both for methyl isobutyl ketone and for methyl ethyl ketone (r = 0.98 and 0.79, respectively). The authors calculated that approximately 0.12% of methyl isobutyl ketone inhaled would be excreted into the urine, and approximately 0.19% of the inhaled methyl ethyl ketone.

Exposure to ethylene glycol monoethyl ether acetate was assessed in two groups of shipyard painters: a “low” exposure group mostly involved with brush painting and other duties (n = 27), and a “high” exposure group involved with spraying or assisting with the spraying (n = 30), along with an unexposed control group (n = 41) (Kim et al., 1999).

Workers in the high-exposure group wore half-mask respirators while the other workers only occasionally wore respiratory protection. Urinary ethoxyacetic acid and methyl hippuric acid was measured for all subjects. The mean and range of inhalation ethylene glycol monoethyl ether acetate exposure concentrations were 3.03 ppm (not detectable to 18 ppm) and 1.76 ppm (not detectable to 8.1 ppm) for the high and low groups, respectively. The geometric mean concentrations of methyl hippuric acid in the three

OCCUPATIONAL EXPOSURE AS A PAINTER 153 exposure groups were 0.08, 0.03, and 0.01 g/g creatinine; the corresponding values for ethoxyacetic acid were 9.2, 0.6, and 0.1 mg/g creatinine. The authors noted that the levels of ethoxyacetic acid that they had measured were lower than in another study of shipyard painters, which they suggested may be due to the wearing of respiratory protection and percutaneous absorption.

Laitinen & Pulkkinen (2005) measured the inhalation exposure to 2-(2-alkoxy)ethoxy ethanols and urinary 2-(2-alkoxyethoxy)acetic acids in a group of floor lacquerers (n = 22).

The 8-hour average inhalation exposures of floor lacquerers to 2-(2-methoxyethoxy)ethanol, 2-(2-ethoxyethoxy)ethanol and 2-(2-butoxyethoxy)ethanol were on average 0.23 ppm, 0.08 ppm, and 0.05 ppm, respectively. The excretion levels of the corresponding metabolites 2-(2-methoxyethoxy)acetic acid, 2-(2-ethoxyethoxy)acetic acid and 2-(2-butoxyethoxy)acetic acid were on average 4.9 mmol/mol creatinine, 9.3 mmol/mol creatinine, and 9.2 mmol/mol creatinine, respectively. A linear relationship was found between the urinary alkoxyethoxy)acetic acid concentrations and the inhalation exposure to 2-(2-alkoxyethoxy)ethanol.

1.5.4 Polycyclic aromatic hydrocarbons

Paints containing coal tar are used in shipyards, for example in the Republic of Korea, and they account for 13% of all shipyard paints used. Lee et al. (2003) used urinary 1-hydroxypyrene glucuronide as a marker of exposure to polycyclic aromatic hydrocarbons (PAHs) in three groups: 111 painters using coal-tar paints, 70 painters using general paints, and 27 on-site controls who used no paint. Average urinary 1-hydroxypyrene glucuronide levels for the group exposed to coal-tar paints was 2.24 μmol/mol creatinine, for general painters 1.38 μmol/mol creatinine, and for the controls 0.62 μmol/mol creatinine. The elevated 1-hydroxypyrene glucuronide in general painters was attributed to bystander exposure from working alongside coal-tar painters and from low levels of PAHs in general paints.

1.5.5 Metals

Higher blood lead levels have been measured in painters involved in paint removal using sand blasting or other mechanical means (Jarrett, 2003). Blood lead levels in 21 workers in two autobody workshops were in the range of 2–38 μg/dL (Enander et al., 2004). The highest levels were found in workers who were involved in sanding painted surfaces and who ate, drank or smoked cigarettes in areas contaminated with lead dust.

Saito et al. (2006) reported results of blood lead monitoring carried out between 1990 and 2000 from more than 7500 workers in 259 lead-handling facilities in Japan. The mean concentration for 82 people painting or baking was 5.4 μg/dL (range 1.4–21.1 μg/dL), which was one of the lowest for the groups of workers studied.

Kiilunen (1994) reported the results from a large database of urinary metal concentrations made by the Finnish Institute of Occupational Health between 1980 and

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1989; 9377 urinary chromium and 3172 urinary nickel analyses were made. The mean end-shift urinary chromium level among the 265 painters in the database was 0.04 μmol/L with 95% of the results being less than 0.12 μmol/L. The corresponding values for urinary nickel were 0.3 and 0.61 μmol/L, although in this case there were only 10 workers for whom data were available.