Sharyn Gaskin

Rhizoremediation of hydrocarbon contaminated soil using Australian native grasses

Rhizoremediation involves the breakdown of contaminants in soil resulting from microbial activity that is enhanced in the plant root zone. The objective of this study was to assess Australian native grasses for their ability to stimulate removal of aliphatic hydrocarbons from a mine site soil. Time-course pot experiments were conducted in a greenhouse with three grass species (Cymbopogon ambiguus, Brachiaria decumbens, and Microlaena stipoides) in a mine site soil experimentally contaminated with a 60:40 diesel:oil mixture at 1% (w/w) concentration. Plants were cultivated for 100days with periodic evaluation of changes in soil total petroleum hydrocarbon (TPH) concentration, soil lipase activity, and abundance of hydrocarbon-degrading microorganisms. Results were compared to unplanted control treatments. Significantly lower endpoint TPH concentrations were recorded in planted soil compared to unplanted soil (p=0.01). Final TPH concentrations and rates of TPH removal varied between grass species, with total TPH removal of between 50% and 88% achieved in planted treatments. The presence of grasses significantly increased the abundance of hydrocarbon-degrading microorganisms and soil lipase activity relative to unplanted soil (p<0.05). Residual TPH concentration was found to be closely (negatively) correlated with abundance of hydrocarbon-degrading microorganisms and to a lesser extent with soil lipase activity. Australian native grass species were identified that effectively enhance the remediation of diesel/oil contaminated soil, without any requirement for nutrient supplementation. Results may have extensive application to the nationwide problems associated with hydrocarbon contaminated sites.

Screening of Australian native grasses for rhizoremediation of aliphatic hydrocarbon-contaminated soil

Rhizoremediation involves the breakdown of contaminants in soil resulting from microbial activity that is enhanced in the plant root zone. The objective of this study was to identify Australian native grass species as suitable candidates for rhizoremediation application. Seeds of nine perennial Australian native grasses were sown in soil from a mine site and artificially contaminated with a 60:40 diesel/oil mixture at concentrations of 1% (w/w), 0.5% (w/w), and 0% (control). Seedling emergence was not adversely affected by the presence of hydrocarbon contamination for all but one grass species. Three promising species (Brachiaria decumbens, Cymbopogon ambiguus, and Microlaena stipoides var. Griffin) were assessed for growth characterization in contaminated and uncontaminated soils. The evaluated species survived for 120 days in the contaminated soil and, in some instances, produced considerably more root biomass in the presence of contamination. C. ambiguus showed growth stimulation in the presence of contamination (1% and 0.5% w/w) with significantly increased root biomass production compared with the control (p = 0.0001). B. decumbens and M. stipoides showed tolerance, without adverse growth effects in the presence of diesel/oil at the exposed concentrations. Stimulation of the rhizosphere microbial population that is capable of degrading diesel/oil was found for all of the species tested, using a most probable number method for enumeration. This investigation has identified suitable candidates for further investigation of their rhizoremediation potential.

Application of skin contamination studies of ammonia gas for management of hazardous material incidents

In an atmospheric HAZMAT release unprotected public dermal exposure is often of short duration, but with potential secondary exposure if not decontaminated promptly. Mass decontamination is resource intensive and needs to be justified. For many HAZMAT agents there is no evidence-base on which to provide guidance on decontamination, particularly for non-symptomatic worried well. It is important to understand the influence of street clothing and environmental and other factors. Ammonia is a common HAZMAT agent and was selected for in vitro human skin studies of absorption, penetration and off-gassing at test concentrations up to 2000 ppm, incorporating primary and secondary exposure combinations up to 60 min. Intact skin provided a good barrier to ammonia penetration. Heavy street clothing such as denim was found to act as an initial barrier to skin absorption but subsequently as a reservoir for secondary exposure, under variable temperature and humidity conditions. Rapid off-gassing was observed for lighter fabrics including polyester and cotton. The findings here have been summarized as a set of practical guidelines for emergency responders who are required to make decisions about ammonia decontamination including for non-symptomatic individuals. This evidence-based diagrammatic approach allows for specific actions based on different atmospheric ammonia concentrations and other parameters.

In-vitro methods for testing dermal absorption and penetration of toxic gases

Abstract This technical note provides details of an experimental technique for in-vitro skin studies with atmospheric chemical challenge. There appear to be major evidence gaps in relation to dermal exposure of gases. We describe a modification of standard OECD protocols for an atmospheric delivery system which can be used to understand interaction of toxic gases and the skin. The system can be used to examine the mechanisms by which skin uptake occurs. Auxiliary components which allow for parameter variation such as temperature and relative humidity are also described. Methodology presented in this technical note uses examples of gas challenges (ammonia, chlorine) to illustrate its application to gases of differing physicochemical properties. This adapted protocol can be applied in the context of HAZMAT scenarios involving atmospheric toxic chemical release and dermal absorption potential under variable exposure conditions.

Isolation and Identification of Pyrene Mineralizing Mycobacterium spp. from Contaminated and Uncontaminated Sources

Mycobacterium isolates obtained from PAH-contaminated and uncontaminated matrices were evaluated for their ability to degrade three-, four- and five-ring PAHs. PAH enrichment studies were prepared using pyrene and inocula obtained from manufacturing gas plant (MGP) soil, uncontaminated agricultural soil, and faeces from Macropus fuliginosus (Western Grey Kangaroo). Three pyrene-degrading microorganisms isolated from the corresponding enrichment cultures had broad substrate ranges, however, isolates could be differentiated based on surfactant, phenol, hydrocarbon and PAH utilisation. 16S rRNA analysis identified all three isolates as Mycobacterium sp. The Mycobacterium spp. could rapidly degrade phenanthrene and pyrene, however, no strain had the capacity to utilise fluorene or benzo[a]pyrene. When pyrene mineralisation experiments were performed, 70–79% of added 14C was evolved as 14CO2 after 10 days. The present study demonstrates that PAH degrading microorganisms may be isolated from a diverse range of environmental matrices. The present study demonstrates that prior exposure to PAHs was not a prerequisite for PAH catabolic activity for two of these Mycobacterium isolates.

Chlorine and hydrogen cyanide gas interactions with human skin: in vitro studies to inform skin permeation and decontamination in HAZMAT incidents.

Accidental or intentional toxic gas releases may result in significant public health and psychological consequences. Management of exposed individuals during HAZMAT incidents should be risk-based and supported by a suitable scientific evidence base. There appear to be large evidence gaps in relation to dermal absorption of gases, as well as management advice for potentially exposed individuals. Chlorine and hydrogen cyanide are two common HAZMAT gases and this paper addresses the need for experimental data tailored to HAZMAT scenarios and first responders. In addition to time variations of gas concentration, the modifying effects of clothing, temperature, and oil-based sunscreen on epidermal absorption and penetration are assessed. Results for chlorine show little penetration up to 500 ppm but with small enhancing effects due to heavy cotton and oil-based sunscreen. Hydrogen cyanide up to 800 ppm shows minor penetration consistent with previous studies, with little variability in the presence of sunscreen and clothing. Practical guidelines to support the decision-making of emergency responders with regard to personal decontamination have been derived.

An Evaluation of Antifungal Agents for the Treatment of Fungal Contamination in Indoor Air Environments

Fungal contamination in indoor environments has been associated with adverse health effects for the inhabitants. Remediation of fungal contamination requires removal of the fungi present and modifying the indoor environment to become less favourable to growth. This may include treatment of indoor environments with an antifungal agent to prevent future growth. However there are limited published data or advice on chemical agents suitable for indoor fungal remediation. The aim of this study was to assess the relative efficacies of five commercially available cleaning agents with published or anecdotal use for indoor fungal remediation. The five agents included two common multi-purpose industrial disinfectants (Cavicide® and Virkon®), 70% ethanol, vinegar (4.0%−4.2% acetic acid), and a plant-derived compound (tea tree (Melaleuca alternifolia) oil) tested in both a liquid and vapour form. Tea tree oil has recently generated interest for its antimicrobial efficacy in clinical settings, but has not been widely employed for fungal remediation. Each antifungal agent was assessed for fungal growth inhibition using a disc diffusion method against a representative species from two common fungal genera, (Aspergillus fumigatus and Penicillium chrysogenum), which were isolated from air samples and are commonly found in indoor air. Tea tree oil demonstrated the greatest inhibitory effect on the growth of both fungi, applied in either a liquid or vapour form. Cavicide® and Virkon® demonstrated similar, although less, growth inhibition of both genera. Vinegar (4.0%–4.2% acetic acid) was found to only inhibit the growth of P. chrysogenum, while 70% ethanol was found to have no inhibitory effect on the growth of either fungi. There was a notable inhibition in sporulation, distinct from growth inhibition after exposure to tea tree oil, Virkon®, Cavicide® and vinegar. Results demonstrate that common cleaning and antifungal agents differ in their capacity to inhibit the growth of fungal genera found in the indoor air environment. The results indicate that tea tree oil was the most effective antifungal agent tested, and may have industrial application for the remediation of fungal contamination in residential and occupational buildings.

Skin Absorption of Ethylene Oxide Gas Following Exposures Relevant to HAZMAT Incidents

Ethylene oxide (EO) is a reactive gas used by numerous industries and medical facilities as a sterilant, a fumigant, and as a chemical intermediate in chemical manufacturing. Due to its common use, EO has been involved in a number of leaks and explosive incidents/accidents requiring HAZMAT response. However, the extent of skin absorption under short-term HAZMAT conditions has not been directly assessed. Such data would assist decision making by first responders regarding skin decontamination in EO HAZMAT incidents. An in vitro test protocol with human skin was used for EO exposures at 800 ppm and 3000 ppm. No evidence of dermal penetration was seen for 800 ppm EO during a 30-min challenge. For 3000 ppm, EO penetration was observed after 20 min and was greater under higher temperature/humidity conditions. Fabric (heavy cotton) on skin enhanced penetration 5-fold compared with naked skin. Off gassing from exposed fabric was rapid. The results show dermal uptake of EO vapour from exposure at 3000 ppm is small but clothing may contribute to further dermal absorption/penetration over time. For exposed, but asymptomatic, persons in EO HAZMAT incidents first responders should remove bulky clothing to prevent potential skin damage and further uptake.

Airborne fungal profiles in office buildings in metropolitan Adelaide, South Australia: Background levels, diversity and seasonal variation

The presence of bioaerosols in indoor non-industrial workplace environments has become an increasing concern to indoor air quality assessors and Occupational Health and Safety professionals. The paucity of workplace survey information and national standards limits the comparisons that can be made when investigating suspected indoor fungal contamination. Data are needed on typical non-problem conditions, thereby providing background survey information. This study examined viable fungi in 128 air samples (89 indoor: 39 outdoor) from office buildings in Adelaide, South Australia, which has an arid Mediterranean climate. Results across four consecutive seasons show that the viable airborne fungal concentrations in indoor air were on average 75% lower than those in outdoor air. A seasonal influence was noted with higher fungal levels in autumn and summer compared with winter and spring. The most common culturable airborne fungi, across all seasons and conditions, were Penicillium, Aspergillus, Cladosporium and Alternaria. A weak correlation between fungal spore concentration in indoor air and carbon dioxide was observed (r = 0.26). No other correlations with indoor air quality parameters were noted. This study provides a profile of airborne fungal diversity and abundance in non-problem indoor environments and practical guidance to indoor air quality assessors on the interpretation of indoor fungal monitoring data.

233 Use of mobile phones and light metre applications in the assessment of the occupational lighting environment

Introduction With a variety of built-in sensors, smartphone users can do many things with only one portable device. Light metre applications measure illuminance and are offered free or at low cost. Like noise metre apps, it is tempting to use such devices for preliminary lighting surveys. However, there are few reports of studies evaluating such use, and none which have explored their potential use for blue light hazards. This paper presents preliminary data on side by side measurements of illuminance and blue light hazard (BLHF) function-weighted illuminance with a range of smartphones, apps and light sources. Methods Phones with Android and Apple iOS operating systems and two phone apps were compared alongside a professional lux metre on a workstation desk in a mock office, set up in a dark room. A blue light filter (Hoya B440) was used directly over the sensors for the approximate BLHF weighted value. Results The values of the illuminance and blue-weighted illuminance differed depending on distances and the types of light sources. The illuminance values for Android and Apple devices using the same software were variable suggesting differences in sensor hardware or circuitry. There were major differences between forward and rear facing sensors. The use of the blue light filter significantly reduced illuminance readings, limiting practical application for some devices. Discussion The rationale for the use of BLHF filters on photometric instrumentation for blue light hazard assessment has been described in the literature. Calibration factors for both naked and filtered sensors need to be established for specific phones and software. The limitations and variances of particular combinations also need to be understood. However, in principle, the use of a smartphone in preliminary lighting surveys may be feasible, and if so, guidance for their use may be developed.