Human exposure limits to hypergolic fuels

Over the past four decades, many studies have been conducted on the toxicities of the rocket propellants hydrazine (HZ) and monomethylhydrazine (MH). Numerous technical challenges have made it difficult to unambiguously interpret the results of these studies, and there is considerable divergence between results obtained by different investigators on the inhalation concentrations (MAC's) for each toxic effect inducible by exposure to hypergolic fuels in spacecraft atmospheres, NASA undertook a critical review of published and unpublished investigations on the toxicities of these compounds. The current state of the art practices for similar studies. While many questions remain unanswered, MAC's were determined using the best available data for a variety of toxic endpoints for potential continuous exposure durations ranging from 1 hour to 180 days. Spacecraft MAC's (SMAC's) were set for each compound based on the most sensitive toxic endpoint at each exposure duration

Human exposure in low Earth orbit

Human exposure to trapped electrons and protons in low Earth orbit (LEO) is evaluated on a basis of a simple approximation of the human geometry for spherical shell shields of varying thickness. A data base is presented that may be used to make preliminary assessment of the impact of radiation exposure constraints on human performance. Detailed shielding studies should be performed before final design considerations. A sample impact assessment is discussed on the basis of presently accepted allowable exposure limits. A brief discussion is given on the anticipated impact of an ongoing reassessment of allowable exposure limits

Risk management policies and practices regarding radio frequency electromagnetic fields: results from a WHO survey

This study aims to describe current risk management practices and policies across the world in relation to personal exposures from devices emitting radiofrequency fields, environmental exposures from fixed installations and exposures in the work environment. Data from 86 countries representing all WHO regions were collected through a survey. The majority of countries (76.8 %) had set exposure limits for mobile devices, almost all (90.7 %) had set public exposure limits for fixed installations and 76.5 % had specified exposure limits for personnel in occupational settings. A number of other policies had been implemented at the national level, ranging from information provisions on how to reduce personal exposures and restrictions of usage for certain populations, such as children or pregnant women to prevention of access around base stations. This study suggests that countries with higher mobile subscriptions tend to have set radiofrequency exposure limits for mobile devices and to have provisions on exposure measurements about fixed installation

Radiation environment and shielding for early manned Mars missions

The problem of shielding a crew during early manned Mars missions is discussed. Requirements for shielding are presented in the context of current astronaut exposure limits, natural ionizing radiation sources, and shielding inherent in a particular Mars vehicle configuration. An estimated range for shielding weight is presented based on the worst solar flare dose, mission duration, and inherent vehicle shielding

Occupational exposure limits for manufactured nanomaterials, a systematic review

The toxicological properties of manufactured nanomaterials (MNMs) can be different from their bulk-material and uncertainty remains about the adverse health effects they may have on humans. Proposals for OELs have been put forward which can be useful for risk management and workers' protection. We performed a systematic review of proposals for OELs for MNMs to better understand the extent of such proposals, as well as their derivation methods. We searched PubMed and Embase with an extensive search string and also assessed the references in the included studies. Two authors extracted the data independently. We identified 20 studies that proposed in total 56 OEL values. Of these, two proposed a generic level for all MNMs, 14 proposed a generic OEL for a category of MNMs and 40 proposed an OEL for a specific nanomaterial. For specific fibers, four studies proposed a similar value but for carbon nanotubes (CNTs) the values differed with a factor ranging from 30 to 50 and for metals with a factor from 100 to 300. The studies did not provide explanations for this variation. We found that exposure to MNMs measured at selected workplaces may exceed even the highest proposed OEL. This indicates that the application and use of OELs may be useful for exposure reduction. OELs can provide a valuable reference point for exposure reduction measures in workplaces. There is a need for more and better supported OELs based on a more systematic approach to OEL derivation

The INDEX Project - Critical Appraisal of the Setting and Implementation of Indoor Exposure Limits in the EU

The INDEX project (Critical Appraisal of the Setting and Implementation of Indoor Exposure Limits in the EU), coordinated by the EU/JRC and funded by DG SANCO, has been finished in December 2004. The project was carried out in collaboration with a Steering Committee of leading European experts in the area of indoor air pollution. Scope of INDEX was to identify priorities and to assess the needs for a Community strategy and action plan in the area of indoor air pollution. The key issues that have been addressed within the project are: - the setting up of a list of compounds to be measured and regulated in indoor environments with priority, on the basis of health impact criteria - to provide suggestions and recommendations on potential exposure limits for these compounds and - to provide information on links with existing knowledge, ongoing studies, legislation etc. at world scale. Suggestions and recommendations on potential exposure limits or other exposure control actions were defined for five prioritised compounds; formaldehyde, nitrogen dioxide, carbon monoxide, benzene, and naphthalene.JRC.I.5-Physical and chemical exposure

Diathermy smoke: hazardous to health?

The heat used in electrocautery causes cells to boil and explode, or simply dry up, producing a gaseous by-product known as diathermy smoke. This smoke may have mutagenic and carcinogenic potential, similar to that of cigarette smoke (Spearman et al, 2007). A search of electronic databases was performed and selected articles were reviewed using the Critical Appraisal Skills Programme (CASP) tool to enable a review of relevant material to be undertaken. The findings of the review identified 45 compounds, 9 of these were found to be hazardous when cross referenced against the Control of Substances Hazardous to Health (COSHH) list of approved workplace exposure limits (Health and Safety Executive (HSE), 2011) and 4 were carcinogens. This research indicates that the use of an extraction device to remove smoke when using diathermy is best practice. However, until more conclusive evidence is available on the actual health risks of diathermy smoke, as opposed to the potential health risks, it will be difficult for organisations that govern health and safety at work to create legislation on the need to extract it from the operating theatre air

Accommodating the Allergic Employee in the Workplace

[Excerpt] Once an employer learns an applicant or employee is allergic, and in need of an accommodation, the employer may be required by the Americans with Disabilities Act to provide the needed accommodation. The allergic worker may be able to respond to low levels of exposure, levels which may be lower than the relevant occupational exposure limits set by OSHA or recommended by agencies such as NIOSH or organizations such as the ACGIH. Accommodating the allergic employee would therefore generally involve reducing exposure further by providing specific protection for the sensitive individual, such as additional protective equipment which the average (nonallergic) worker probably wouldn\u27t need. Protective equipment could involve the use of respirators for respiratory protection or protective clothing (such as gloves) or barrier creams for skin protection. The use of respirators would involve employer compliance with OSHA\u27s Respiratory Protection Standard (29 CFR 1910.134) including the use of a physical to determine whether a worker could wear a respirator. Battery-powered respirators may enable those with pulmonary or cardiovascular problems to still use a respirator. Respirators made of silicone may enable someone to wear a respirator who has a rubber allergy (such as an allergy to mercaptobenzothiazole)

Space radiation dose analysis for solar flare of August 1989

Potential dose and dose rate levels to astronauts in deep space are predicted for the solar flare event which occurred during the week of August 13, 1989. The Geostationary Operational Environmental Satellite (GOES-7) monitored the temporal development and energy characteristics of the protons emitted during this event. From these data, differential fluence as a function of energy was obtained in order to analyze the flare using the Langley baryon transport code, BRYNTRN, which describes the interactions of incident protons in matter. Dose equivalent estimates for the skin, ocular lens, and vital organs for 0.5 to 20 g/sq cm of aluminum shielding were predicted. For relatively light shielding (less than 2 g/sq cm), the skin and ocular lens 30-day exposure limits are exceeded within several hours of flare onset. The vital organ (5 cm depth) dose equivalent is exceeded only for the thinnest shield (0.5 g/sq cm). Dose rates (rem/hr) for the skin, ocular lens, and vital organs are also computed

A heuristic tool for exposure reduction in indoor wireless networks

A heuristic indoor network planner for exposure calculation and optimization in wireless networks is developed. The model for the electric-field strength in the vicinity of an access point is presented and the WiFi networks are optimized in order not to exceed a maximal electric-field strength at a certain separation from the access points. The influence of the maximally allowed field strength and the assumed minimal separation between the access point and the human is assessed for a typical office building