We observed previously that polymorphisms in glutathione S-transferase (GST) genes modified allergic responses to diisocyanate exposure. Here, we extended the study to examine the possible role of N-acetyltransferase (NAT) genotypes in the development of diisocyanate-induced ill effects, both separately and in combination with the previously examined GSTM1, GSTM3, GSTP1 and GSTT1 genotypes. The study population comprised 182 diisocyanate-exposed workers, 109 of whom were diagnosed with diisocyanate-induced asthma and 73 of whom had no symptoms of asthma. The diisocyanates to which the workers had been exposed to were diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI) and toluene diisocyanate (TDI). The NAT2 genotype did not have any significant effect on the risk of developing asthma, but the putative slow acetylator NAT1 genotypes posed a 2.54-fold risk of diisocyanate-induced asthma (95% confidence interval [CI] 1.32 to 4.91). The effect of the NAT1 genotype was especially marked for workers exposed to TDI, among whom the NAT1 slow acetylator genotypes posed a 7.77-fold risk of asthma (95% CI 1.18 to 51.6). Statistically significant increases in asthma risk were also observed among the whole study population for the concurrent presence of the GSTM1 null genotype and either NAT1 (odds ratio [OR] 4.53, 95% CI 1.76 to 11.6) or NAT2 (OR 3.12, 95% CI 1.11 to 8.78) slow acetylator genotypes, and of NAT1 and NAT2 slow acetylator genotypes (OR 4.20, 95% CI 1.51 to 11.6). The results suggest for the first time that in addition to GSTs, the NATs play an important role in inception of asthmatic reactions related to occupational exposure to diisocyanates.

Exposure to diisocyanates was assessed by biological monitoring among workers exposed to the thermal degradation products of polyurethanes (PURs) in five PUR-processing environments. The processes included grinding and welding in car repair shops, milling and turning of PUR-coated metal cylinders, injection moulding of thermoplastic PUR, welding and cutting of PUR-insulated district heating pipes during installation and joint welding, and heat-flexing of PUR floor covering. Isocyanate-derived amines in acid-hydrolysed urine samples were analysed as perfluoroacylated derivatives by gas chromatography mass spectrometry in negative chemical ionisation mode. The limits of quantification (LOQs) for the aromatic diamines 2,4- and 2,6-toluenediamine (2,4- and 2,6-TDA) and 4,4'-methylenedianiline (4,4'-MDA) were 0.25 nmol l(-1), 0.25 nmol l(-1) and 0.15 nmol l(-1), respectively. The LOQ for the aliphatic diamines hexamethylenediamine (HDA), isophoronediamine (IpDA) and 4,4'-diaminodicyclohexyl methane (4,4'-DDHM) was 5 nmol l(-1). TDA and MDA were detected in urine samples from workers in car repair shops and MDA in samples from workers welding district heating pipes. The 2,4-TDA isomer accounted for about 80% of the total TDA detected. No 2.6-TDA was found in the urine of non-exposed workers. The highest measured urinary TDA and MDA concentrations were 0.79 nmol mmol(-1) creatinine and 3.1 nmol mmol(-1) creatinine, respectively. The concentrations found among non-exposed workers were 0.08 nmol mmol(-1) creatinine for TDA and 0.05 nmol mmol(-1) creatinine for MDA (arithmetic means). Exposure to diisocyanates originating from the thermal degradation of PURs are often intermittent and of short duration. Nevertheless, exposure to aromatic diisocyanates can be identified by monitoring diisocyanate-derived amines in acid-hydrolysed urine samples.

The psbC gene encodes the intrinsic chlorophyll protein CP 43, a component of photosystem II in higher plants, green algae, and cyanobacteria. Oligonucleotide-directed mutagenesis was used to introduce mutations into the portion of psbC that encodes the large extrinsic loop E of CP 43 in the cyanobacterium Synechocystis 6803. Three mutations, E293Q, E339Q, and E352Q, each produced a strain with impaired photosystem II activity. The E293Q mutant strain grew photoautotrophically at rates comparable to the control strain. Immunological analyses of several PS II components indicated that this mutant accumulated normal quantities of PS II proteins. However, this mutant evolved oxygen to only 56% of control rates at saturating light intensities. Measurements of total variable fluorescence yield indicated that this mutant assembled approximately 60% of the fully functional PS II centers found in the control strain. The E339Q mutant grew photoautotrophically at a severely reduced rate. Both immunological analysis and variable fluorescence yield experiments indicated that E339Q assembled a normal complement of PS II centers. However, this mutant was capable of evolving oxygen to only 20% of control rates. Variable fluorescence yield experiments demonstrated that this mutant was inefficient at using water as an electron donor. Both E293Q and E339Q strains exhibited an increased (approximately 2-fold) sensitivity to photoinactivation. The E352Q mutant was the most severely affected. This mutant failed to grow photoautotrophically and exhibited essentially no capacity for oxygen evolution. Measurements of total variable fluorescence yield indicated that this mutant assembled no functional PS II centers. Immunological analysis of isolated thylakoid membranes from E352Q revealed a complete absence of CP 43 and reduced levels of both the D1 and manganese-stabilizing proteins. These results suggest that the mutations E293Q and E339Q each produce a defect associated with the oxygen-evolving complex of photosystem II. The E352Q mutation appears to affect the stability of the PS II complex. This is the first report showing that alteration of negatively charged residues in the CP 43 large extrinsic loop results in mutations affecting PS II assembly/function.

The aim of this work was to establish whether workers at sawmills where chlorophenol-containing anti-stain agents had been previously used were still exposed to chlorophenols. A gas chromatographic-mass spectrometric (GC-MS) procedure for the determination of chlorophenols in urine was developed. Chlorophenols were determined from hydrolysed urine as acetylated derivatives and determined by GC-MS using selected ion monitoring (SIM). Isolation of the chlorophenols with toluene gave the best extraction efficiencies (65-119%). Stability tests at -20 degrees C showed no degradation of the chlorophenols studied during 6 months. The limit of quantification was 3.6 ng mg-1 creatinine for 2,4,6-trichlorophenol, 5.5 ng mg-1 for 2,3,4,6-tetrachlorophenol and 3.6 ng mg-1 for pentachlorophenol. Traces of 2,4,6-trichlorophenol, 2,3,4,6-tetrachlorophenol and pentachlorophenol were found both in previously exposed workers and in non-exposed controls, the urinary concentrations ranging from 1.1 to 15.9 ng mg-1 creatinine. The concentrations of urinary chlorophenols in previously exposed workers were of the same magnitude as those found in non-exposed controls and in the general population. The results show that it is unlikely that sawmill workers would be currently occupationally exposed to chlorophenols or polychlorinated dibenzo-p-dioxins and dibenzofurans via a contaminated work environment.