Hazardous waste operations and emergency response (HAZWOPER) sites throughout the United States confront airborne hazards daily. The same is true on construction sites. Many of these hazardous materials have distinctive odors, but when assessed to be well within their respective occupational exposure limits, they are referred to as nuisance odors (Fundamentals of Industrial Hygiene). According to OSHA’s HAZWOPER Standard, 29 CFR 1910.120, medical surveillance becomes a requirement when an employee is exposed to hazardous substances when there is evidence that there has been an exposure exceeding the material’s occupational exposure limit for 30 or more days within a 12-month period (OSHA). As such, nuisance odors, by themselves, are not typically considered as health hazards.

World’s largest cleanup site
Let’s consider nuisance odors in the context of the cleanup of the Hanford Department of Energy (DOE) site in Richland, Washington. Hanford is undergoing a concerted effort toward the remediation of legacy issues associated with the production of plutonium (PU-239) during the eras of World War II (Manhattan Project) and the Cold War (DOE-2008).

During the 1950s through the 1970s, studies were conducted to understand the biological effects due to intake and uptake of fissile material, such as strontium- 90. Experimentation involved animal test subjects where routes of exposure of ingestion, inhalation as well as intraperitoneal injection were studied. Upon death, a final assay was conducted, followed by discarding the carcass remains (including excreta products collected throughout the process) in trenches located within close proximity to the laboratory facilities (Dorian, Richards, 1978).

Hazard assessment
Due to environmental regulations, the animal remains needed to be retrieved and transported to a regulated transportation, storage and disposal (TSD) facility. Information pertaining to animal remains was reviewed. Because the material was buried 30 to 50 years ago, it was expected that biological decomposition should have resulted in negligible remains (bones, skin, etc). It was concluded health effects due to decomposition products would not be present to any substantial degree to cause adverse health effects (Brounstein, February, 2006). Nevertheless assessment methods were employed.

Strong odors stop work
Field remediation began in mid-January, 2006. Within the first hour of excavation, animal carcasses and bagged excrement were unearthed. Immediately, strong odors saturating the air resulted in a number of workers experiencing the classic symptoms nausea and headaches due to acute contaminant exposure due to inhalation. While the odors were prevalent throughout the remediation site, all direct-reading instrumentation indicated non-detect concentrations. At this point work stopped while hazard identification, assessment and controls were reviewed. The first step was to review potential health hazards. This required an in-depth look at the decomposition process to understand what health hazards should be considered.

The decomposition process
The decomposition process can be divided into six stages:

Stage 1: Still Living -While living, organisms are not outwardly decomposing. However the intestines contain a diversity of bacteria, protozoans and nematodes. Some of these micro-organisms are ready for a new life, should the host die.

Stage 2: Initial Decay -Although shortly after death the body appears fresh from the outside, the microorganisms described in Stage 1 begin to digest the intestine itself. They eventually break out of the intestine and start digesting the surrounding internal organs.

From the moment of death, flies are attracted to the corpse and begin to lay eggs around wounds and natural body openings (mouth, nose, eyes, anus, genitalia). These eggs hatch and move into the body, often within 24 hours.

Stage 3: Putrefaction -Bacteria break down tissues and cells, releasing fluids into body cavities. Through anaerobic respiration various gases including hydrogen sulfide and methane, are produced. They are very attractive to a variety of insects.

Young maggots move throughout the body, spreading bacteria, secreting digestive enzymes and tearing tissues with their mouth hooks.

The rate of decay increases, and the smells and body fluids that begin to emanate from the body attract more blowflies, flesh flies, beetles and mites.

Stage 4: Black Putrefaction - The bloated body eventually collapses, leaving a flattened body whose flesh has a creamy consistency. The exposed parts of the body are black in color and there is a very strong smell of decay.

By this stage, several generations of maggots are present on the body and some have become fully grown. They migrate from the body and bury themselves in the soil where they become pupae.

Stage 5: Butyric Fermentation - All the remaining flesh is removed over this period and the body dries out. It has a cheesy smell, caused by butyric acid, and this smell attracts a new suite of corpse organisms.

Predators and parasitoids are still present at this stage including numerous wasps and beetle larvae.

Stage 6: Dry Decay -The body is now dry and decays very slowly. Eventually all the hair disappears leaving the bones only.

Animals that can feed on hair include tineid moths, and micro-organisms like bacteria. Mites, in turn, feed on these micro-organisms.

They remain on the body as long as traces of hair remain, which depends on the amount of hair that covers the particular species. Humans and pigs have relatively little hair and this stage is short for these species. (Australian Museum, 2003)

Decomposition products and health effects
The NIOSH publication, “Criteria for Controlling Occupational Hazards in Animal Rendering Processes” has identified many potential health risks due to chemicals as well as biologic hazards due to carcasses. NIOSH notes that sanitation and personnel hygiene as well as medical pre-placement exams are necessary controls. While inhalation hazards due to work in rendering plants were not recognized as a primary concern, NIOSH does recognize that respiratory protection may be considered when specific chemicals are encountered. However, NIOSH does not mention the possibility of respirators within the context of biologic decomposition.

In another CDC publication, “Health Recommendations for Relief Workers Responding to Disasters,” it discusses immunizations for travel overseas, as well as precautions relating to weather conditions and psychological/emotional stressors. The CDC continues to discuss the importance of hand washing (with soap) to remove potentially infectious material from the skin to help prevent the transmission of both respiratory and enteric diseases. The CDC also mentions the use of waterless alcohol-based hand rubs. However respiratory protection is not discussed.

So, while literature has documented that adverse health effects should not be encountered, and that respiratory protection is not a consideration, the question needs to be asked, how can odors cause the health reactions experienced by the field employees during such work?

In conclusion
While evidence suggests that odorants do not cause direct toxicological effects to the various biologic systems, they can influence such systems to the point of causing observable health effects. While strong odors may exist at HAZWOPER work sites, the risk of pathogenic disease has yet to be established. Though decomposition products may result in health effect symptoms (i.e. headaches, nausea, etc), traditional industrial hygiene sampling is not designed (i.e. lacks the sensitivity) to determine if odor-causing chemicals are responsible for persons exhibiting the varied reactions. Such physical reactions may be the result of memory patterns created from prior experiences, which, in turn, have established chemical-electric pathways.

Until all the questions are satisfied, industrial hygienists must continue to communicate the hazards and controls to the workforce. Through such efforts, knowledge and understanding will follow, thus effecting worker anxiety toward a positive direction. This pertains to all safety and health hazards; not just airborne contaminants with low odor thresholds.

Editor's Note:Visit www.ishn.com, June 2010 issue feature articles, for the full listing of references for this article.