Greg Kennedy

Occupational and Environmental Exposure of Garage Workers and Taxi Drivers to Airborne Manganese Arising from the Use of Methylcyclopentadienyl Manganese Tricarbonyl in Unleaded Gasoline

Occupational and environmental exposure to airborne manganese has been measured for two groups of workers in Montreal, taxi drivers and garage mechanics. In Canada methylcyclopentadienyl manganese tricarbonyl (MMT) has replaced lead as an anti-knock agent in gasoline and represents a potentially important source of manganese contamination for the population in general and for the two chosen groups of workers in particular. Twenty workers (10 taxi drivers and 10 garage mechanics) wore a personal air sampler for five consecutive working days and two off-work periods. The amount of total Mn on each filter was determined by neutron activation analysis and then converted to atmospheric Mn concentrations. The values obtained varied from 0.004 microgram m-3 to 2.067 micrograms m-3. At work the garage mechanics were exposed to an average of 0.250 microgram m-3 and the taxi drivers to 0.024 microgram m-3. Off-work, the two groups were exposed respectively to an average of 0.007 microgram m-3 and 0.011 microgram m-3. In the garages there was twice as much Mn in the air on days when the doors were closed compared to days when they were left opened (0.314 micrograms m-3/0.152 microgram m-3). The levels found in this study remain well below the established limits for occupational and environmental airborne exposure. These results will lead to further studies to positively identify the source of Mn as MMT and to explore other pathways leading to the contamination of the general population.

Bioaccumulation and locomotor effects of manganese phosphate/sulfate mixture in Sprague-Dawley rats following subchronic (90 days) inhalation exposure

Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic manganese (Mn) compound added to unleaded gasoline in Canada. The primary combustion products of MMT are Mn phosphate, Mn sulfate, and a Mn phosphate/Mn sulfate mixture. Concerns have been raised that the combustion products of MMT containing Mn could be neurotoxic, even at low levels of exposure. The objective of this study is to investigate exposure-response relationships for bioaccumulation and locomotor effects following subchronic inhalation exposure to a mixture of manganese phosphates/sulfate mixture. A control group and three groups of 30 male Sprague-Dawley rats were exposed in inhalation chambers for a period of 13 weeks, 5 days per week, 6 h a day. Exposure concentrations were 3000, 300, and 30 microg/m(3). At the end of the exposure period, locomotor activity and resting time tests were conducted for 36 h using a computerized autotrack system. Rats were then euthanized by exsanguination and Mn concentrations in different tissues (liver, lung, testis, and kidney) and blood and brain (caudate putamen, globus pallidus, olfactory bulb, frontal cortex, and cerebellum) were determined by neutron activation analysis. Increased manganese concentrations were observed in blood, kidney, lung, testis, and in all brain sections in the highest exposure group. Mn in the lung and in the olfactory bulb were dose dependent. Our data indicate that the olfactory bulb accumulated more Mn than other brain regions following inhalation exposure. Locomotor activity was increased at 3000 microg/m(3), but no difference was observed in resting time among the exposed groups. At the end of the experiment, rats exposed to 300 and 3000 microg/m(3) exhibited significantly decreased body weight in comparison with the control group. Biochemical profiles also revealed some significant differences in certain parameters, specifically alkaline phospatase, urea, and chlorate.

Human Exposure to Respirable Manganese in Outdoor and Indoor Air in Urban and Rural Areas

Methylcyclopentadienyl manganese tricarbonyl (MMT) is used as an additive in gasoline, and its combustion leads to the emission of Mn particles, which increase atmospheric metal con-centrations. The objective of this study was to determine the level of outdoor and indoor respirable Mn (MnR) in Montreal, Canada, where MMT has been used since 1976. Ten women were involved in this study: five living in an urban area, near an expressway with high traffic density, and five residing in a rural area characterized by low traffic density. Outdoor and indoor air samples were collected each week (5 in total) during 3 consecutive days; blood sam-ples were collected at the end of the air sampling period. The average concentration of out-door MnR in the urban area was 0.025 μg/m3, which is significantly different from the average of 0.005 μg/m3 found in the rural area. The average indoor MnR concentration was also signif-icantly different between the urban area (0.017 μg/m3) and the rural area (0.007 μg/m3). The average outdoor MnR concentrations were not significantly different from the average MnR indoor concentrations within both areas. The mean blood Mn concentrations were not signifi-cantly different between the two groups. Data suggest that a high outdoor atmospheric MnR leads to a high indoor MnR, but not to an increase in blood Mn levels.

BIOACCUMULATION AND LOCOMOTOR EFFECT OF MANGANESE DUST IN RATS

The primary goal of this study is to determine the effects of Mn exposure via inhalation. The bioaccumulation of Mn in different organs and tissues, the alteration of biochemical parameters, and the locomotor activity were assessed. A group of 26 male Sprague-Dawley rats (E) were exposed to 3750 µg/m3 of Mn dust for 6 h/day, 5 days/wk for 13 consecutive weeks and compared to a control group of 12 rats (C) exposed to 4 µg/m3. After exposure, neurological evaluation was carried out for 36 h (a night-day-night cycle) using a computerized autotrack system. Rats were then sacrificed by exsanguination, and Mn content in organs and tissues was determined by neutron activation analysis. Mn concentrations in lung, putamen, and cerebellum were significantly higher in E than in C (0.30 vs. 0.17, 0.89 vs. 0.44, 0.63 vs. 0.48 ppm; p < .01), as well as in the kidney, frontal cortex, and globus pallidus (1.15 vs. 0.96, 0.84 vs. 0.47, 1.28 vs. 0.55 ppm; p < .05). Potassium concentration was significantly lower in E than in C (5.11 vs. 5.79 mmol/L; p < .05), as was alkaline phosphatase (106.9 vs. 129.6 U/L; p < .01). Locomotor activity indicated higher distance covered in the first 12-h period for E (45 383 vs. 36 098 cm; p < .05) and lower resting time in the last 12-h period for E (36 326 vs. 37 393 s; p < .05). This study is the first of several ongoing studies in our laboratory that address health concerns associated with inhalation exposure to different Mn species and to different levels of exposure.

Occupational and Environmental Exposure of Automobile Mechanics and Nonautomotive Workers to Airborne Manganese Arising from the Combustion of Methylcyclopentadienyl Manganese Tricarbonyl (MMT)

Inhalation exposure to manganese (Mn) was measured for a group of garage mechanics and a control group of nonautomotive workers. The airborne Mn exposure of 35 garage mechanics suspected of being relatively highly exposed to Mn from MMT was measured at the workplace over one-week period. It also was measured for 30 nonautomotive workers at the University of Montreal. The environmental exposure also was measured for the two groups, as was the exposure to three other metals, aluminum (Al), iron (Fe), and zinc (Zn). At work the mechanics were exposed to Mn concentrations varying from 0.010 to 6.673 micrograms m-3 with a mean of 0.45 microgram m-5, while the control group was exposed to concentrations varying from 0.011 to 1.862 microgram m-3 with a mean of 0.04 microgram m-3. The mean environmental exposure for the two groups was similar to the Mn concentrations gathered in Montreal in 1992. Workplace concentrations of Al, Fe, and Zn also were higher for the garage mechanics. The results suggest that less than 10% of the Mn exposure of the garage mechanics was due to MMT. The levels of the metals measured were below the established limits for industrial and even environmental exposure.

Variations of trace element concentrations in red spruce tree rings

The potential of coniferous trees as biological indicators of heavy metal atmospheric pollution was investigated. In 31 municipalities of an industrialized region, samples of wood from the trunks of red spruce (Picea rubens) were taken to determine the spatial distribution of accumulated metals. Using the annual rings, these core samples were divided into 5-yr sections to determine temporal variations. The concentrations of Mg, Al, Ca, Mn, Fe, Cu, and Zn were measured by neutron activation analysis. All metals showed the highest concentrations in the most recent wood and the bark. For the wood older than 5 yr, Mn and Zn are stable with time, Mg and Ca decrease, while Al, Fe, and Cu appear to increase. A statistical analysis showed the municipalities with the highest variations in metal concentrations; it also revealed correlations in the fluctuations of several of the metals. As expected, trees in towns near metal refineries contain higher amounts of Mn, Fe, and Al. Large variations in metal concentrations, due to factors not totally understood, were observed. Thus, red spruce is not a sensitive bio-indicator of atmospheric metal pollution.

Emission rates and physico-chemical characteristics of Mn particles emitted by vehicles using Methylcyclopentadienyl Manganese Tricarbonyl (MMT) as an octane improver

Since 1990, methylcyclopentadienyl manganese tricarbonyl (MMT) has been added to all gasoline in Canada as an antiknock agent. The objective of this study is to determine the percentage of manganese emitted by different types of automobiles and to evaluate the size and chemical characteristics of the Mn-containing particles. Nine vehicles with different mileage and engine capacity were tested using standard procedures for urban and highway driving cycles. One ran on gasoline without MMT and served as a control. The particles were collected using two separate systems: a trapping device consisting of a water tank connected to the tailpipe and a pumping device linked to a cassette containing Teflon filters. Water samples were analyzed by neutron activation to determine the amount of Mn emitted at the tailpipe for each test. Teflon filters were analyzed by electron microscopy to determine the size and the chemical characteristics of the particles. The amount of manganese emitted from the tailpipe varied from 4 to 41% of the manganese consumed, depending on the driving cycle and the vehicle. For the urban cycle, the emission rate was positively correlated with previous mileage. Almost all particles found on teflon filters had a size less than 5 μm. They appeared to be mainly Mn oxides but other elements could be masked by the gold and paladium peaks.

Trace metal contamination in and on Balsam fir (Abies balsamea (L) Mill.) foliage in southern Quebec, Canada

Atmospheric trace metal contamination in and on forest foliage in southern Quebec has been investigated. Washed and unwashed foliage of Balsam fir from seven sampling sites with different elevation were analyzed by NAA. Metal element concentrations in needles were generally well below the suggested levels of potential phytotoxicity, except for Mn. At three rural mountain sampling locations, Mn concentration exceed 600 μg/g in washed and unwashed needles. The variability of metal concentrations between individual trees at a given site showed the expected element-specific differences, with most CVs < 50%. The variation of metal deposits on needle surfaces (ng/cm2) with elevation and sampling site depended on the element concerned. The input of Al, As, Cr, La, Sb, Sc, Sm, and V, accompanying Fe in deposits on the foliage surface, may mainly come from atmospheric deposition in the form of soil dust and air pollution. Wet deposition samples from Roundtop Mountain suggest cloud immersion as a significant trace element deposition pathway in high elevation forest.

Uptake and translocation of 54Mn and 65Zn applied on foliage and bark surfaces of balsam fir [Abies balsamea (L.) Mill.] seedlings

Abstract Uptake and translocation of 54Mn and 65Zn in balsam fir [Abies balsamea (L.) Mill.] seedlings were studied with the radioisotopes applied directly on shoot or main-stem surfaces in a growth chamber. Concentration and distribution of the absorbed radioisotopes in different plant parts depended on distances between source (the application site) and sink (the rest of the seedling), as well as on tissue growth activity. Acidic wetness significantly enhanced radioisotope absorption. 54Mn and 65Zn were found to be concentrated primarily in 1-year old needles at the middle and top levels of the seedling crown. There were significant (P

Oral manganese intake estimated with dietary records and with direct chemical analysis.

The estimation of the daily oral intake of manganese (Mn) can vary significantly with the method used. This study aims to compare two different approaches: the use of dietary records along with tables of the Mn contents of different foods and the parallel collection of identical aliquots which are analyzed for Mn. Dietary samples and information were collected during a 3-day dietary assessment with five participants. The average daily oral intake of Mn estimated from the dietary records and tables of Mn contents was 3.52 mg/day (S.D. = 1.9), which corresponds to an exposure dose (ED) of 50.27 microg/kg body wt./day (S.D. = 26.2). With a parallel collection of identical aliquots and chemical analysis, the average intake was 2.88 mg/day (S.D. = 0.64) for an ED of 41.18 microg/kg body wt./day (S.D. = 8.9). Thus, the use of tables gives an estimated oral dose 22% higher than the more accurate direct chemical analysis.