RESUMEN
Glyphosate, aminomethylphosphonic acid (AMPA), imazapyr, sulfometuron methyl (SMM), and metsulfuron methyl (MSM) were measured in streamwater collected during and after a routine application of herbicides to a forestry site in Oregon's Coast Range. Samples were collected at 3 stations: HIGH at the fish-no-fish interface in the middle of the harvest and spray unit, MID at the bottom of the unit, and LOW downstream of the unit. All herbicides were applied by helicopter in a single tank mix. AMPA, imazapyr, SMM, and MSM were not detected (ND) in any sample at 15, 600, 500, and 1000 ng/L, respectively. A pulse of glyphosate peaking at approximately equal to 62 ng/L manifested at HIGH during the application. Glyphosate pulses peaking at 115 ng/L (MID) and 42 ng/L (HIGH) were found during the first 2 postapplication storm events 8 and 10 days after treatment (DAT), respectively: glyphosate was less than 20 ng/L (ND) at all stations during all subsequent storm events. All glyphosate pulses were short-lived (4-12 h). Glyphosate in baseflow was approximately equal to 25 ng/L at all stations 3 DAT and was still approximately equal to 25 ng/L at HIGH, but ND at the other stations, 8 DAT: subsequently, glyphosate was ND in baseflow at all stations. Aquatic organisms were subjected to multiple short-duration, low-concentration glyphosate pulses corresponding to a cumulative time-weighted average (TWA) exposure of 6634 ng/L × h. Comparisons to TWA exposures associated with a range of toxicological endpoints for sensitive aquatic organisms suggests a margin of safety exceeding 100 at the experimental site, with the only potential exception resulting from the ability of fish to detect glyphosate via olfaction. For imazapyr, SMM, and MSM the NDs were at concentrations low enough to rule out effects on all organisms other than aquatic plants, and the low concentration and (assumed) pulsed nature of any exposure should mitigate this potential. Integr Environ Assess Manag 2017;13:396-409. © 2016 SETAC.
Asunto(s)
Organismos Acuáticos/fisiología , Herbicidas/toxicidad , Contaminantes Químicos del Agua/toxicidad , Animales , Oregon , Medición de Riesgo/métodosRESUMEN
Under the terms of the Clean Water Act, criteria for the protection of human health (Human Health Ambient Water Quality Criteria [HHWQC]) are traditionally derived using equations recommended by the US Environmental Protection Agency (USEPA) that include parameters for exposure assessment. To derive "adequately protective" HHWQC, USEPA proposes the use of default values for these parameters that are a combination of medians, means, and percentile estimates targeting the high end (90th percentile) of the general population. However, in practice, in nearly all cases, USEPA's recommended default assumptions represent upper percentiles. This article considers the adequacy of the exposure assessment component of USEPA-recommended equations to yield criteria that are consistent with corresponding health protection targets established in USEPA recommendations or state policies, and concludes that conservative selections for exposure parameters can result in criteria that are substantially more protective than the health protection goals for HHWQC recommended by USEPA, due in large part to the compounding effect that occurs when multiple conservative factors are combined. This situation may be mitigated by thoughtful selection of exposure parameter values when using a deterministic approach, or by using a probabilistic approach based on data distributions for many of these parameters.
Asunto(s)
Exposición a Riesgos Ambientales , Monitoreo del Ambiente , Contaminantes Químicos del Agua/análisis , Calidad del Agua , Humanos , Medición de Riesgo , Estados Unidos , United States Environmental Protection Agency , Calidad del Agua/normasRESUMEN
Because many herbicides selectively control specific species or types of vegetation, they are often applied as mixtures to achieve better control over undesirable vegetation. When herbicides are applied in forest ecosystems, streams, ponds, and other bodies of water are typically protected by buffer zones in which no herbicide is applied. However, in some landscapes, small wetlands and streams are difficult to see and avoid, thus the potential acute toxicity of herbicide mixtures to aquatic organisms is of interest, yet it has not been well-studied. We examined the acute toxicity of 23 different herbicide mixtures to Ceriodaphnia dubia and fathead minnows (Pimephales promelas) at environmentally relevant concentrations, and, where possible, characterized mixture interactions using Marking's Additive Index. Maximum exposure concentrations were equivalent to applying the maximum allowable rate for each component directly to the surface of a 6-in. deep pond with no dissipation following application. Under the conditions of this study, herbicide formulations containing Accord Concentrate (glyphosate), Arsenal AC (imazapyr), Chopper (imazapyr), Escort (metsulfuron methyl), Oust XP (sulfometuron methyl), and Velpar L (hexazinone) were not associated with appreciable acute toxicity to fathead minnows or C. dubia when used alone or in mixtures with each other and various surfactants and adjuvants. Herbicide mixtures for which Additive Indexes could be calculated exhibited primarily antagonistic or simple additive toxicity. In the few cases where synergistic toxicity was observed, the degree of synergism was slight, never exceeding approximately twice the effect estimated based on additive toxicity. Based on the results of this study, neither acute toxicity nor enhanced acute aquatic toxicity due to synergistic mixture effects appears to be a significant concern for applications of the herbicide mixtures most commonly used in forestry.
Asunto(s)
Cladóceros/efectos de los fármacos , Cyprinidae , Herbicidas/toxicidad , Contaminantes Químicos del Agua/toxicidad , Animales , Ecosistema , Agricultura Forestal , Tensoactivos/toxicidad , Pruebas de Toxicidad AgudaRESUMEN
Managed forests are a primary land use within the Coastal Plain of the southern United States. These forests are generally managed under standards, guidelines, or regulations to conserve ecosystem functions and services. Economic value of commercial forests provides incentives for landowners to maintain forests rather than convert them to other uses that have substantially reduced environmental benefits. In this review, we describe the historical context of commercial forest management in the southern United States Coastal Plain, describe how working forests are managed today, and examine relationships between commercial forest management and maintenance of functional aquatic and wetland systems and conservation of biological diversity. Significant challenges for the region include increasing human population and urbanization and concomitant changes in forest area and structure, invasive species, and increased interest in forest biomass as an energy feedstock. Research needs include better information about management of rare species and communities and quantification of relationships between ecosystem attributes and forest management, including biomass production and harvest. Incentives and better information may help commercial forest managers in the Coastal Plain more efficiently contribute to landscape-scale conservation goals.
Asunto(s)
Conservación de los Recursos Naturales , Agricultura Forestal , Agricultura Forestal/historia , Historia del Siglo XX , Sudeste de Estados UnidosRESUMEN
Six different brands of passive card monitors representing three different types of card monitor were evaluated for their effectiveness in testing for hydrogen sulfide in workplace atmospheres. The cards were evaluated both in the laboratory and in a kraft pulp mill according to a protocol that closely follows that recommended by the National Institute for Occupational Safety and Health and other researchers for passive samplers. The performances of the Envirometrics Air-Chem Technologies and the Gilian ChemAir quantitative cards, the Gilian ChromAir and VICI Metronics Colortec semiquantitative cards, and the American Gas & Chemical Co. Leak-Tec and Gilian SafeAir indicator cards were evaluated. The detection limits of the cards were determined, and the cards were exposed to a range of hydrogen sulfide concentrations (1, 5, 10, 20 ppm), face velocities (0, 50 ft/min), and temperature/humidity combinations (95 degrees F/90% humidity, 77 degrees F/50% humidity, 40 degrees F/20% humidity). The cards' responses to short-term and variable concentration exposures as well as to the potential interferents methyl mercaptan, dimethyl sulfide, dimethyl disulfide, sulfur dioxide, and carbon monoxide were assessed. Each of the cards tested demonstrated a usefulness for the detection and/or quantification of hydrogen sulfide at concentrations and under conditions relevant to kraft pulp mill workplace atmospheres. Which card is best depends on the application, sampling conditions, and level of confidence necessary in the results. The Gilian ChemAir quantitative card performed well under most conditions with acceptable accuracy (13% lab, 26% field), and no response to potential interferents or to changes in face velocity, temperature, and humidity. The Envirometrics ACT quantitative cards did not perform as well, with an accuracy level of only 46% in the lab. They also seemed to be more affected by changes in face velocity, temperature, and humidity. Both semiquantitative cards (Gillian ChromAir, VICI Metronics Colortec) provided reasonable approximations of hydrogen sulfide levels in the range of the hydrogen sulfide occupational exposure levels although the VICI card had a much lower detection limit. Neither performed well at high temperature and humidity. The response of VICI card was more affected by changes in face velocity, whereas the Gilian ChromAir showed some response to reduced sulfur gas interferents. Both indicator cards (Leak-Tec, Gilian SafeAir) performed well, responding to 20 ppm hydrogen sulfide within 1 min and to 5 ppm within 5 min. Neither was significantly affected by extremes of temperature and humidity.
Asunto(s)
Contaminantes Atmosféricos/análisis , Monitoreo del Ambiente/instrumentación , Sulfuro de Hidrógeno/análisis , Exposición Profesional , Lugar de Trabajo , Movimientos del Aire , Humanos , Humedad , Industrias , Papel , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , TemperaturaRESUMEN
The RespiCon is a multistage virtual impactor that can be used as either a personal or an area sampler. Particles collected on the first stage of the RespiCon represent the respirable fraction of airborne particulate matter. Particles collected on the first and second stages represent the thoracic fraction, and particles collected on the first, second, and third stages represent the inhalable fraction. The RespiCon is available in two versions, one with photometric aerosol detection and a gravimetric version. In this study, the performance of the gravimetric version was examined in various forest products industry facilities. The precision of the RespiCon was assessed and its performance was compared with that of both a respirable cyclone and an inhalable dust sampler. In addition, some RespiCon samples were examined using scanning electron microscopy to determine physical particle size distribution. Under the conditions of this testing, the RespiCon appeared to be reasonably precise. For most sampling locations there was a close correspondence between measurements made with the RespiCon and the CIS personal inhalable sampler or the BGI-4 respirable cyclone. The results of microscopic examination of filters from the RespiCon were consistent with expected performance characteristics. The RespiCon is a useful sampling device for those situations in which it is important to simultaneously collect either personal or area samples of the respirable, thoracic, and inhalable fractions of airborne particulate matter.