Characterization of chemical contaminants generated by a desktop fused deposition modeling 3-dimensional Printer

Printing devices are known to emit chemicals into the indoor atmosphere. Understanding factors that influence release of chemical contaminants from printers is necessary to develop effective exposure assessment and control strategies. In this study, a desktop fused deposition modeling (FDM) 3-dimensional (3-D) printer using acrylonitrile butadiene styrene (ABS) or polylactic acid (PLA) filaments and two monochrome laser printers were evaluated in a 0.5 m³ chamber. During printing, chamber air was monitored for vapors using a real-time photoionization detector (results expressed as isobutylene equivalents) to measure total volatile organic compound (TVOC) concentrations, evacuated canisters to identify specific VOCs by off-line gas chromatography-mass spectrometry (GC-MS) analysis, and liquid bubblers to identify carbonyl compounds by GC-MS. Airborne particles were collected on filters for off-line analysis using scanning electron microscopy with an energy dispersive x-ray detector to identify elemental constituents. For 3-D printing, TVOC emission rates were influenced by a printer malfunction, filament type, and to a lesser extent, by filament color; however, rates were not influenced by the number of printer nozzles used or the manufacturer's provided cover. TVOC emission rates were significantly lower for the 3-D printer (49–3552 µg h^?1) compared to the laser printers (5782–7735 µg h^?1). A total of 14 VOCs were identified during 3-D printing that were not present during laser printing. 3-D printed objects continued to off-gas styrene, indicating potential for continued exposure after the print job is completed. Carbonyl reaction products were likely formed from emissions of the 3-D printer, including 4-oxopentanal. Ultrafine particles generated by the 3-D printer using ABS and a laser printer contained chromium. Consideration of the factors that influenced the release of chemical contaminants (including known and suspected asthmagens such as styrene and 4-oxopentanal) from a FDM 3-D printer should be made when designing exposure assessment and control strategies.     

An evaluation of employee exposure to volatile organic compounds in three photocopy centers

Personal and area samples from three copy centres were collected in thermal desorption tubes and analyzed using gas chromatography-mass spectrometry. Real-time personal total volatile organic compounds (TVOC) were measured using a data-logging photoionization detector. Fifty-four different VOCs were detected in the area samples. The maximum concentration measured was 1132.0 ppb (toluene, copy center 3, day 1). Thirty-eight VOCs were detected in the personal samples and concentrations ranged from 0.1 ppb (1,1-biphenyl, p-dichlorobenzene, propylbenzene, styrene, and tetrachloroethylene) to 689.6 ppb (toluene). Real-time TVOC measurements indicated daily fluctuations in exposure, ranging from <71 to 21,300 ppb. The time-weighted average exposures for the photocopier operators on days 1 and 2 were 235 and 266 ppb and 6155 and 3683 ppb, in copy centers 2 and 3, respectively. Personal exposure measurements of individual VOCs were below accepted occupational standards and guidelines. For example, the maximum concentration was 0.3% of the permissible exposure limits (toluene, copy center 3). Exposures were highest in copy center 3; this is likely due to the presence of offset printing presses. It is concluded that photocopiers contribute a wide variety of VOCs to the indoor air of photocopy centers; however, exposures are at least 100 times below established standards.     

Assessment of the indoor air quality in copy centres at Aveiro,Portugal

This study presents continuous measurements of size-segregated particulate matter, total volatile organic compounds, ozone, formaldehyde, comfort parameters (temperature and relative humidity), CO and CO₂ at two copy centres (A and B) in Aveiro, Portugal. PM₁₀ samples collected with low-volume samplers were used to determine the carbonaceous content (organic and elemental carbon) by a thermo-optical technique. Mean PM₁₀ levels of 55.8?±?7.50 μg m^?3 and 51.3?±?9.35 μg m^?3 were obtained in copy centres A and B, respectively. The 24-h indoor PM₁₀ concentration at both copy centres exceeded the protection limit established by the Portuguese legislation. Around 60 % of the PM₁₀ were composed of particles with sizes below 2.5 μm. On average, organic carbon accounted for 27.6 % (copy centre A) and 18.6 % (copy centre B) of the PM₁₀ mass indoors, whereas a lower mass fraction of 11.5 % was found for both outdoor spaces. The much higher indoor levels of organic carbon suggest significant contribution by indoor sources. The ozone level increased in both copy centres when the photocopiers started to work. Mean ozone levels (0.055?±?0.005 and 0.048?±?0.006 ppm in copy centres A and B, respectively) during business hours may exceed the standard recommended for workplaces (0.05 ppm), representing a cause of possible adverse health effects on employees. The indoor-to-outdoor ozone concentration ratios were greater than 1 in both centres, indicating an important contribution of indoor sources. Formaldehyde levels remained always below the World Health Organisation guideline for indoor air (0.1 mg m^?3). Total concentrations of volatile organic compounds were also relatively low, in general ranging from around 190 to 300 ppb. The indoor-to-outdoor concentration ratios were in the range between 0.70 and 0.76. Results showed that operation of laser printers can lead to high particulate matter and ozone concentration indoors. Pollutants associated with printing equipment have potential to cause adverse health effects if exposures are sufficiently high. Precautions should be taken to minimise the risks of exposed workers.     

Proposed maximum permissible exposure limits for ultrashort laser pulses

Recent studies have provided considerable ED50 data for both visible and near infrared wavelengths from single laser pulses below one nanosecond of exposure. The current ANSI Z136.1 standard does not offer an approved maximum permissible exposure limit for subnanosecond single laser pulses and the current suggested maximum permissible exposure limit may be overly conservative. Lacking an approved standard industrial, medical, educational, and military uses of these types of laser systems may be limited or prohibited. A new set of laser maximum permissible exposure limits for subnanosecond visible and near infrared single laser pulses is recommended, along with the steps taken to develop the proposed standard.     

Is 3D printing safe? Analysis of the thermal treatment of thermoplastics: ABS,PLA, PET,and nylon

The fast development of low-cost desktop three-dimensional (3D) printers has made those devices widely accessible for goods manufacturing at home. However, is it safe? Users may belittle the effects or influences of pollutants (organic compounds and ultrafine particles) generated by the devices in question. Within the scope of this study, the authors attempt to investigate thermal decomposition of the following commonly used, commercially available thermoplastic filaments: acrylonitrile-butadiene-styrene (ABS), polylactic acid (PLA), polyethylene terephthalate (PET), and nylon. Thermogravimetric analysis has shown the detailed thermal patterns of their behavior upon increasing temperature in neutral atmosphere, while GC analysis of organic vapors emitted during the process of heating thermoplastics have made it possible to obtain crucial pieces of information about the toxicity of 3D printing process. The conducted study has shown that ABS is significantly more toxic than PLA. The emission of volatile organic compounds (VOC) has been in the range of 0.50 µmol/h. Styrene has accounted for more than 30% of total VOC emitted from ABS, while for PLA, methyl methacrylate has been detected as the predominant compound (44% of total VOCs emission). Moreover, the authors have summarized available or applicable methods that can eliminate formed pollutants and protect the users of 3D printers. This article summarizes theoretical knowledge on thermal degradation of polymers used for 3D printers and shows results of authors’ investigation, as well as presents forward-looking solutions that may increase the safety of utilization of 3D printers.     

Antipyrine clearance during experimental and occupational exposure to toluene.

Exposure to toluene vapour enhances hepatic microsomal enzyme function in animals as assessed by the metabolism of the test drug antipyrine. Thirty six printing trade workers with long term occupational exposure to a mixture of organic solvents and 39 matched controls were randomly allocated into four groups. Eighteen printers and 21 controls were exposed to 100 ppm of toluene during 6.5 hours in an exposure chamber. The remaining 18 printers and 18 controls were exposed to 0 ppm of toluene under similar conditions. The salivary clearance of antipyrine was measured immediately after the stay in the exposure chamber to investigate a possible acute change in liver function and was repeated two weeks later, shortly before the summer vacation. Antipyrine clearance was measured again at the end of the summer vacation-four weeks after exposure. To study a possible effect of chronic exposure on antipyrine clearance 12 printing trade workers with 17 years (median) of occupational exposure to toluene vapour at concentrations of about 100 ppm were investigated before and four weeks after cessation of exposure. No difference in antipyrine clearance was found either within the groups or between the groups at any of the measurements.     

Fume emissions from a low-cost 3-D printer with various filaments

3-D printing is an additive manufacturing process involving the injection of melted thermoplastic polymers, which are then laid down in layers to achieve a pre-designed shape. The heated deposition process raises concerns of potential aerosol and volatile organic compounds (VOC) emission and exposure. The decreasing cost of desktop 3-D printers has made the use of 3-D printers more acceptable in non-industrial workplaces lacking sufficient ventilation. Meanwhile, little is known about the characteristics of 3-D printing fume emission. The objective of this study was to characterize aerosols and VOC emissions generated from various filaments used with a low-cost 3-D printer in an environmental testing chamber. A pre-designed object was printed in 1.25 hours using eight types of filaments. A scanning mobility particle sizer and an aerodynamic particle sizer were employed to measure the particle size distribution in sub-half-micron fraction (<0.5 µm) and super-half-micron fraction (0.5–20 µm), respectively. VOC concentration was monitored real-time by a photoionization detector and sampled with a tri-sorbent thermal desorption tube, and analyzed by thermal desorption gas chromatography mass spectrometry (TD-GC/MS). Results showed high levels of fume particles emission rate (1.0 × 10⁷ to 1.2 × 10¹⁰ #/min) in the sub-half-micron range with mode sizes of 41–83 nm. Particle concentrations peaked during the heat-up and solid layer printing periods. Total VOC concentration in the chamber followed a first-order buildup, with predominant VOC species in the chamber were breakdown and reaction products of the filaments, such as styrene from ABS filaments. These findings and exposure scenario estimation suggest that although the VOC concentrations were much lower than occupational exposure limits, particles with size less than micron might be a concern for users of low-cost 3-D printers due to high respirablity, especially if used in settings without proper guidance and engineering control.     

Measurement of secondary products during oxidation reactions of terpenes and ozone based on the PTR-MS analysis: effects of coexistent carbonyl compounds

Continuous measurements using proton transfer reaction mass spectrometry (PTR-MS) can be used to describe the production processes of secondary products during ozone induced oxidation of terpenes. Terpenes are emitted from woody building materials, and ozone is generated from ozone air purifiers and copy machines in indoor environments. Carbonyl compounds (CCs) are emitted by human activities such as smoking and drinking alcohol. Moreover, CCs are generated during ozone oxidation of terpenes. Therefore, coexistent CCs should affect the ozone oxidation. This study has focused on the measurement of secondary products during the ozone oxidation of terpenes based on the use of PTR-MS analysis and effects of coexistent CCs on oxidized products. Experiments were performed in a fluoroplastic bag containing α-pinene or limonene as terpenes, ozone and acetaldehyde or formaldehyde as coexistent CCs adjusted to predetermined concentrations. Continuous measurements by PTR-MS were conducted after mixing of terpenes, ozone and CCs, and time changes of volatile organic compounds (VOCs) concentrations were monitored. Results showed that, high-molecular weight intermediates disappeared gradually with elapsed time, though the production of high-molecular weight intermediates was observed at the beginning. This phenomenon suggested that the ozone oxidation of terpenes generated ultrafine particles. Coexistent CCs affected the ozone oxidation of α-pinene more than limonene.     

Indoor air pollutants in office environments: Assessment of comfort,health, and performance

Concentrations of volatile organic compounds (VOCs) in office environments are generally too low to cause sensory irritation in the eyes and airways on the basis of estimated thresholds for sensory irritation. Furthermore, effects in the lungs, e.g. inflammatory effects, have not been substantiated at indoor relevant concentrations. Some VOCs, including formaldehyde, in combination may under certain environmental and occupational conditions result in reported sensory irritation. The odour thresholds of several VOCs are low enough to influence the perceived air quality that result in a number of acute effects from reported sensory irritation in eyes and airways and deterioration of performance. The odour perception (air quality) depends on a number of factors that may influence the odour impact. There is neither clear indication that office dust particles may cause sensory effects, even not particles spiked with glucans, aldehydes or phthalates, nor lung effects; some inflammatory effects may be observed among asthmatics. Ozone-initiated terpene reaction products may be of concern in ozone-enriched environments (≥0.1 mg/m³) and elevated limonene concentrations, partly due to the production of formaldehyde. Ambient particles may cause cardio-pulmonary effects, especially in susceptible people (e.g. elderly and sick people); even, short-term effects, e.g. from traffic emission and candle smoke may possibly have modulating and delayed effects on the heart, but otherwise adverse effects in the airways and lung functions have not been observed. Secondary organic aerosols generated in indoor ozone-initiated terpene reactions appear not to cause adverse effects in the airways; rather the gaseous products are relevant. Combined exposure to particles and ozone may evoke effects in subgroups of asthmatics.     

Study of the genotoxicity of toluene

Chromosome analysis was conducted for peripheral lymphocytes of 23 printers exposed to toluene concentrations of 590 mg/m3 in a rotary machine workshop and to rotogravure printing inks. The percentages of aberrant cells were 2.30 in the printers and 1.46 in the control group (n = 22) (p < .05). The concentration of hippuric acid in printers was significantly higher than in the control group (p < .01), and the level of blood toluene at the end of the workshift was 0.500 mg/l. The authors also examined rotogravure printing inks-considered a potential source of genotoxic polycyclic aromatic hydrocarbons because they contained carbon black-their use in printing plants, and previous documentation of increased chromosomal aberrations in rotogravure printers. Only milligrams of fluorene and phenanthrene per gram of the printing inks were found; no polycyclic aromatic hydrocarbons with carcinogenic properties were discovered in the inks. The authors used Salmonella typhimurium indicator strains TA 98, TA 100, TA 1537, and YG 1041 in spot tests and indicator strains TA 98 and TA 100 in plate-incorporation assays to determine that there was no bacterial mutagenicity of all four colors of rotogravure inks. Urinary mutagenicity, which was evaluated with a microsuspension assay containing YG 1041 indicator strain both in the presence and absence of metabolic activation, was also studied. No significant difference in bacterial mutagenicity was found between the exposed and control groups. The increased percentage of aberrant cells in printers can be explained by exposure to genotoxicants that are not excreted in urine. Toluene was the most likely cause of the aberration.     

装修后办公大楼空气中有机物污染状况及健康效应研究

目的了解装修竣工后不同时期办公大楼空气中主要挥发性有机物的污染状况及对人群健康的影响,为制定相应的防制对策提供依据。方法选择25幢装修竣工后不同时期的办公大楼,分别于装修竣工后30 d、1年、2年,测定室内空气中甲醛、苯、甲苯、二甲苯、TVOC的浓度,同时对办公人员健康状况进行调查。结果甲醛在装修后1年的浓度最高,均值为(0.220±0.050)mg/m3,装修后2年的甲醛平均浓度仍显著地高于对照组(P<0.01)。而苯系物和TVOC的浓度在装修后30 d最高,以后逐渐降低。甲苯、二甲苯平均浓度严重超标,分别超出我国《室内空气质量标准》最高容许浓度的16.2、13.1倍,苯和TVOC浓度超标相对较少。装修竣工时间越短,皮肤和上呼吸道刺激的发生率就越高,但眼部刺激症状的最高发生率却出现在装修后1年的时段里,而且在1年以上的发生率仍显著地高于对照组。结论办公大楼装修能造成室内严重挥发性有机物污染,对办公人员健康危害较大。     

Comparison between urinary o-cresol and toluene as biomarkers of toluene exposure

The characteristics of urinary o-cresol (o-C) and urinary toluene (TOL-U) as biomarkers of occupational exposure to toluene were comparatively evaluated. One hundred healthy male rotogravure printing workers and 161 male and female control subjects were studied. Personal exposure to airborne toluene (TOL-A) during the shift was determined as a time-weighted average. Simple analytical procedures based on solid phase microextraction followed by gas chromatography/mass spectometry analysis were applied to the determination of end-shift o-C and TOL-U. Median TOL-A was 48 (6.0-162.0) mg/m3 in printers and 0.021 (<0.003-0.137) mg/m3 in controls. o-C was 0.185 (0.032-0.948) mg/g creatinine in printers and 0.027 (<0.006-0.330) mg/g creatinine in the controls. TOL-U was 7.6 (1.8-23.9) microg/L in printers and 0.140 (0.094-0.593) microg/L in the controls. According to all indices, exposure to toluene was higher in printers than in the controls. Nevertheless, the distribution of o-C in the two groups partially overlapped, whereas such behavior was not found in TOL-U. Both o-C and TOL-U in printers were correlated with TOL-A (Pearson's on log10-transformed variables r = 0.704 and 0.844, respectively) and with each other (r = 0.683). Smoking habits significantly increased the excretion of o-C but not of TOL-U. From the point of view of sampling conditions and analytical requirements, TOL-U and o-C showed similar properties, but comparison of their intrinsic characteristics showed that TOL-U had higher specificity and sensitivity, lower background values, was better correlated with airborne exposure, and was not influenced by cigarette smoking. Therefore TOL-U may be considered superior to o-C as a biomarker of occupational exposure to toluene.     

Formation and transport of ozone and other photochemical oxidants

Photochemical oxidants (O3, PAN, HCHO) are the typical pollutants in photochemical Smog. They can be formed as the result of the sunlight induced oxidation of precursor pollutants emitted into the atmosphere (NOx, CxHy). Other important precursor substances and reactive intermediates are compounds of the organic hydroxyl group (-O-H, for instance the methoxy radical CH3O), hydroxyl radical .OH, hydroperoxy radical HO2, and singlet oxygen O. For the production of photochemical oxidants in smog, especially ozone, NOx primarily act as catalysator. But CxHy serve as "combustibles". The quantities of the several formed photooxidants are mainly dependent on intensity and duration of daily sunshine, temperature, oxidant concentrations at the beginning of a build-up period, and on emission rates and concentrations of primary pollutants (NO, CxHy). Maximum mixing ratios of secondary pollutants often occur at certain distances downwind of primary pollutant sources, dependent on meteorological conditions (wind velocity, rel. humidity, etc.) and on rate constants for oxidant formation cycles. During the period of July 5 to 11, 1984, for instance, 6 kilometers SW from Zürich we found maximum ground-level mixing ratios of about 150 ppbv ozone, 4 ppbv PAN and 9 ppbv formaldehyde, that is 5 (ozone) to 10 (PAN) times above the supposed oxidant concentrations of unpolluted continental air. The increase in ozone in the late morning and early afternoon is accompanied by an increase in PAN and HCHO and by a decrease in NOx. This shows that in this case HCHO originates from photochemical reactions rather than being emitted directly to the atmosphere from vehicles.(ABSTRACT TRUNCATED AT 250 WORDS)     

Occupational laryngitis caused by formaldehyde: A case report

Formaldehyde is commonly accepted to be an allergen and irritant. However, specifically diagnosed occupational respiratory diseases caused by formaldehyde are relatively rare. Occupational laryngitis was diagnosed in a 47-year-old dairy foreman. He had been exposed for 9 years to formaldehyde emitted from a milk-packing machine situated underneath his office. His exposure level varied considerably. Under normal process conditions, the measured formaldehyde level was 0.03 mg/m³. The patient was examined by different specialists over 1½ years. It was concluded that that he had psychogenic dysphonia. However, a specific laryngeal provocation test with formaldehyde carried out at the Finnish Institute of Occupational Health was positive. His laryngitis was so serious that he was pensioned. During the 3 years of follow-up his condition gradually worsened. He now reacts especially to tobacco smoke and other air impurities known to contain formaldehyde. © 1996 Wiley-Liss, Inc.     

Study of the Genotoxicity of Toluene

Chromosome analysis was conducted for peripheral lymphocytes of 23 printers exposed to toluene concentrations of 590 mg/m³ in a rotary machine workshop and to rotogravure printing inks. The percentages of aberrant cells were 2.30 in the printers and 1.46 in the control group (n = 22) (p < .05). The concentration of hippuric acid in printers was significantly higher than in the control group (p < .01), and the level of blood toluene at the end of the workshift was 0.500 mg/l. The authors also examined rotogravure printing inks—considered a potential source of genotoxic polycyclic aromatic hydrocarbons because they contained carbon black—their use in printing plants, and previous documentation of increased chromosomal aberrations in rotogravure printers. Only milligrams of fluorene and phenanthrene per gram of the printing inks were found; no polycyclic aromatic hydrocarbons with carcinogenic properties were discovered in the inks. The authors used Salmonella typhimurium indicator strains TA 98, TA 100, TA 1537, and YG 1041 in spot tests and indicator strains TA 98 and TA 100 in plate-incorporation assays to determine that there was no bacterial mutagenicity of all four colors of rotogravure inks. Urinary mutagenicity, which was evaluated with a microsuspension assay containing YG 1041 indicator strain both in the presence and absence of metabolic activation, was also studied. No significant difference in bacterial mutagenicity was found between the exposed and control groups. The increased percentage of aberrant cells in printers can be explained by exposure to genotoxicants that are not excreted in urine. Toluene was the most likely cause of the aberration.     

Occupational exposure to toluene: neurotoxic effects with special emphasis on drinking habits

Summary Neurotoxic effects of toluene were examined in 43 male rotogravure printers exposed to toluene (age 27–63, mean 41 years; duration of exposure 11–40, mean 22 years) and 31 male offset printers of the same age with slight exposure to aliphatic hydrocarbons. A neurological examination, tests for autonomic nervous function, electroencephalography, psychological tests and computerized tomography of the brain were carried out in addition to a standardized interview. Exposure levels were evaluated for each person separately on the basis of his work history and the results of an earlier study on exposure levels at the same printing shops. Besides a thorough history of alcohol consumption, information about the printers' drinking habits was obtained from the occupational health care centers of the printing shops. The examinations found only slight abnormalities, and there were no statistically significant group differences in the prevalences of abnormalities. No correlations between the abnormalities and the exposure indices were found either. One of the retired workers, however, who had been exposed to high toluene concentrations for over 40 years, had been diagnosed as having chronic organic solvent intoxication. Heavy drinkers of alcohol were clearly more common in the toluene-exposed group. This study detected no clinically significant abnormalities attributable to toluene alone among workers exposed to 68–185 ppm (mean 117) of toluene for over 10 years. The connection between alcohol consumption and toluene exposure is interesting and deserves further study.     

Organic solvents in the indoor air of two small factories and surrounding houses

Summary For a period of one week the presence of organic solvents, e.g. toluene, xylene and MEK, was investigated (environmental monitoring) in the indoor air of a car-body repair shop, an offset printing office and their surrounding houses. Concurrently the individual exposure of employees and residents was investigated by biological monitoring of the exhaled breath with additional personal air sampling of the employees. Both the car-body repair shop and the offset-printing office proved to be a source of organic solvents for the houses situated above. The concentrations in both factories were lower than 5% of the respective Dutch MAC-values. In the houses situated above the concentrations were distinctly higher than the concentrations in the referent houses. The dispersion of the organic solvents was predominantly vertical. Concentrations decreased with the increase of the distance from the source, but accummulation occurred in the top floor of the building. At the concentrations found, environmental monitoring provided the best method of obtaining reliable information about the exposure of employees and of the residents of adjacent houses.     

Acute and subacute symptoms among workers in the printing industry.

The study population comprised 52 male printers and 52 controls. Each person was interviewed about job history, general health, and work-related symptoms. Symptoms from eyes and airways, neurological symptoms, and general symptoms were recorded. A lung function test and a measurement of the sense of smell were also carried out. The printers had significantly more eye, airway, and neurological symptoms than the controls; the main complaints being irritation of eyes, nose, throat, and a reduced sense of taste. The neurological symptoms were disorders of vision, vertigo, feeling of intoxication, and headache. Furthermore, abdominal pain and flatulence occurred more often among the printers. The symptoms showed no relation to age or job seniority, but neurological and general symptoms were related to shift work. No difference in lung function was found between the two groups. The printers had a slightly lower threshold of smell than the controls. Although the total load due to organic solvents and dust in the air was far below legal limits, the number of magnitude of symptoms experienced by the printers exceeded what is supposed when norms for workroom exposure are set. It is suggested that either the irritative effects of solvents are underestimated or the assumption of additive effects when great numbers of solvents are found does not hold true. A reduction of the number of solvents by eliminating the most toxic solvents or by using dyes without solvents is suggested.     

成都市畜禽血制品中甲醛含量及膳食暴露评估

摘要:目的　分析成都市畜禽血制品中甲醛本底含量及污染状况,并对畜禽血制品中甲醛的风险进行初步评估。方法　对全市范围内畜禽血制品中甲醛含量进行测定,结合成都市居民膳食消费数据,计算成都市居民甲醛暴露量及安全限值（MOS）,采用点评估的方法开展成都市居民摄入畜禽血制品中甲醛的风险评估。结果　畜禽血制品及新鲜畜禽血中甲醛平均含量（中位数）分别为2.51 mg/kg、2.53 mg/kg,但是在畜禽血制品中明显存在个别甲醛含量极高的现象,最高值为3200.00 mg/kg。采用平均暴露量的点评估模型获得的畜禽血制品中甲醛急、慢性暴露的MOS分别是780、2500,而采用高端暴露量的点评估模型获得的甲醛急、慢性暴露的MOS分别是0.5、0.9。结论　成都市大部分畜禽血制品可能会有一个较低的本底含量,但不排除部分的畜禽血制品中甲醛含量极高,提示可能存在一个人为添加的过程。采用高端暴露量评估提示该物质对人体健康的风险超过了可以接受的限度,应当采取适当的风险管理措施。     

Wavelength dependence of ocular damage thresholds in the near-ir to far-ir transition region: proposed revisions to MPES

This report summarizes the results of a series of infrared (IR) laser-induced ocular damage studies conducted over the past decade. The studies examined retinal, lens, and corneal effects of laser exposures in the near-IR to far-IR transition region (wavelengths from 1.3-1.4 mum with exposure durations ranging from Q-switched to continuous wave). The corneal and retinal damage thresholds are tabulated for all pulsewidth regimes, and the wavelength dependence of the IR thresholds is discussed and contrasted to laser safety standard maximum permissible exposure limits. The analysis suggests that the current maximum permissible exposure limits could be beneficially revised to (1) relax the IR limits over wavelength ranges where unusually high safety margins may unintentionally hinder applications of recently developed military and telecommunications laser systems; (2) replace step-function discontinuities in the IR limits by continuously varying analytical functions of wavelength and pulsewidth which more closely follow the trends of the experimental retinal (for point-source laser exposures) and corneal ED50 threshold data; and (3) result in an overall simplification of the permissible exposure limits over the wavelength range from 1.2-2.6 mum. A specific proposal for amending the IR maximum permissible exposure limits over this wavelength range is presented.