How Sub-limit Hydrocarbon Exposure Impacts Eye and Respiratory Irritation

Abstract

In an industrial environment today, many employees experience discomfort due to the chemical exposure. This is a result of following some outdated permissible exposure limits set forth by the Occupational Safety and Health Administration (OSHA), and the application of some obsolete sensory irritation models (United States Department of labor, 2014, para.1). Organic compounds such as hydrocarbons are inadequately characterized, this further complicates the issue. Existing sensory irritation models for organic compounds make use of animal models and exposure periods are not comparable to the actual workplace (Blaszkewicz, Kiesswetter, Schaper, Seeber, & van Thriel, 2005). This further signifies the importance of developing new and modified models capable of handling present day situations well. In order to create more developed and realistic models the existing ones need to consider individual variability into theory as well. The proposed experimental study will investigate how sub-limit Hydrocarbon exposure impacts eye and respiratory irritation in participants at Bayway oil refinery located in New Jersey, through the use of objective and subjective measures. Data analysis will be conducted based on descriptive and inferential statistics, as well as linear regression. The study will provide further insight and understanding into the relationship between hydrocarbon exposure, objective and subjective responses, and health hazards due to prolonged exposure. The results can be utilized to propose and develop enhanced sensory irritation models to advise an appropriate chemical sub-limit exposure in an industrial environment.

Table of Contents

Click to expand Table of Contents

Introduction

Research Problem

Review of Literature and Deficiencies

Significance of the Study

Purpose Statement

Theoretical Perspective

Research Questions

Literature Review

Permissible Exposure Limits

Sensory Irritation and Health Impacts

Current Models

Importance of Objective Measurements

Importance of Subjective Measurements

Proposed Methodologies

Methodology

Participants

Measurement Instruments

Procedure

Limitations

Data Analysis

Conclusion

References

Introduction

Research Problem

In the midst of resurgence of quality and safety control in manufacturing industries in the United States, employees are troubled with sensory irritation on a daily basis. This is the case for most workers in the production sector who are reporting adverse symptoms due to chemical exposure at sub-limit levels which are considered to be harmless by safety experts. Sensory irritation is the irritation of the eyes, nose, and throat in the presence of airborne chemicals, and it represents an endpoint in occupational toxicology (Matovinovic, Salmon, & Shusterman, 2006).

Although the Occupational Safety and Health Administration (OSHA) sets regulatory limits and aims to provide protection for workers from experiencing negative health effects, about 95% of these limits are set for less than 500 chemicals and they “are dangerously out of date and do not adequately protect workers” (United States Department of Labor, 2014, para. 3). In addition to these derelictions, today there are thousands of potentially health hazardous chemicals commercially available and they lack any sort of regulatory limits. A substantial number of chemical compounds that cause sensory irritation fall in these categories (Gaffney & Paustenbach, 2007).

Moreover, organic compounds such as hydrocarbon in particular are inadequately characterized due to the application of obsolete models for sensory irritation which are irrelevant in an industrial environment (Blaszkewicz, Kiesswetter, Schaper, Seeber, & van Thriel, 2005). Prolonged exposure to petroleum products containing various forms of hydrocarbons may even cause chronic obstructive pulmonary diseases in extreme conditions. As a result of the deficiencies mentioned, there is an urgent need to update the current sensory irritation models and assess occupational exposure limits and its subsequent consequences.

Review of Literature and Deficiencies

In 2002, The American Industrial Hygiene Association (AIHA) issued a white paper calling for the updating of the permissible exposure limits. This paper requested for a peer-reviewed guideline on the derivation of exposure limits using the best scientific information available in order to establish process consistency (AIHA, 2002). However, further review of the literature suggested that more accurate models need to be developed first for this to happen.

Researchers who are working on the existing literature have agreed upon the deficiencies it faces and now attempt to remedy the situation by understanding the factors and components necessary to develop a robust model. Animal models that were used in the past to optimize the permissible exposure limits are now undergoing simulations to verify whether it satisfies the present day conditions for dealing hydrocarbons. And from these simulations, it has been determined that potential extrapolation issues occur when using animal models.

Moreover, many of the existing models cannot be applied in an industrial environment due to practical difficulties (Blaszkewicz et al., 2005). The current literature also faces the shortage of human studies, and Dalton (2002) suggests how significant the human data is to understand responses to irritants. Another factor that influences the model is the subjective measures. According to studies subjective measures originating from factors such as odor perception and personality traits play an important role in deciding how an individual responds to chemical exposure. This implies that the individual variability needs to be included too in order to develop a more effective model. Dalton (2002) again stresses on the fact that quantifying the effects of this bias on sensory irritation can be a key ingredient in making a suitable model.

Many methodologies have been worked on so far to address the situation at hand. One such methodology is a chemosensory model which suggests to categorize industrial chemicals into three or more groups depending on their chemical properties such as odor, texture that causes sensory irritation (Gaffney and Paustenbach, 2007). And the data obtained from this test can be utilized to set certain criteria to determine exposure limits. Since the study takes into account objective and subjective measures, certain equations to determine sensory irritation thresholds need to be included as well. The literature also utilizes specific electrodes and tape recorders with microphones to quantify objective measures and various Likert scales for subjective measures. The current literature also takes into account the adverse health hazards caused due to exposure to harmful hydrocarbons.

Although most of the symptoms caused by exposure appear to be generally transitory and reversible, clinical examinations show that in extreme situations it might lead to fatal conditions. These symptoms seems to be caused due to concentration peaks rather than long exposure durations. Some of these symptoms include cyanosis, persistent cough and other obstructive pulmonary ailments. Hydrocarbon ingestion and inhalation in extreme conditions might also cause neurologic symptoms, including drowsiness, poor coordination, stupor or coma and even seizure (Holtz, Tschopp, Soderstrom, Boillat, & Gutzwiller, 1992).

Although efforts have been made to create a satisfactory model that measure sensory irritation, deficiencies still exist in understanding the relationship between objective and subjective measures with the concentration levels (Dalton, 2002). Additional research needs to be conducted in order to determine the linkage between these factors.

Moreover, additional attention needs to be given to characterize organic compounds such as hydrocarbons that are commercially available. The current composition of these organic compounds may differ from the ones used to set permissible exposure limits in the past (Daughtrey, McKee, & Medeiros, 2005). Although timely updates are carried out to input the symptoms caused by exposure to hydrocarbons, deficiencies still exist in understanding the full scope of health impacts. Therefore, there is still room for additional research to quantify the relationship between objective and subjective measures with concentration levels exposed to and plot its correlation with the occurrence of hazardous respiratory ailments and allergies.

Significance of the Study

This study will further investigate the relationship between objective and subjective measures with hydrocarbon concentration levels and develop a better understanding of the human response to sensory irritation. Improved sensory irritation thresholds can be generated from the information gathered in this study. Moreover, by applying various methodologies assessment of permissible exposure limits for organic compounds such as hydrocarbons can be carried out as requested by OSHA. In addition, hydrocarbons that were not classified in the previous list of exposure limits can be included and this information can be utilized in industries where these compounds are used widely.

Purpose Statement

The purpose of this study is to quantify the relationship between the hydrocarbon concentration levels at which the participants are exposed to and their objective and subjective responses at Bayway Refinery in New Jersey. This study also dives into the topic of hazardous health conditions caused due to prolonged exposure to hydrocarbon. The independent variable will be defined as the concentration of hydrocarbon exposed to. The dependent variable will be defined as the participants’ objective and subjective responses to various concentration levels.

Theoretical Perspective

Dalton and Smeets (2005) proposes a theory which contains two approaches that invokes a response in human beings. This theory is founded on cognitive-perceptual methodologies and examines how ones perception is affected by internal and psychological processes (Dalton & Smeets, 2005). The two approaches are commonly known as top-down and bottom-up approaches. A stimulus within the environment causes bottom-up processing. Trigeminal nerves located in the eye, nose, upper respiratory tract and mouth when stimulated by a sensory irritation, such as burning or tingling initiates this form of processing. Whereas, prior beliefs, knowledge, or past experiences initiates top-down processing.

According to Dalton and Smeets bottom-up processing occurs only at high level exposure to organic compounds, while sensory irritations can occur even at low levels as a result of top-down processing. This theory stresses on the significance of using both approaches and as a result both forms of processing needs to be taken into consideration when developing sensory irritation models that defines permissible exposure limits.

Worldview

A post-positivist worldview is applied in this experimental study in order to determine how causes impact outcomes. The aim of this study is to determine the relationship between the concentration levels of hydrocarbons at which participants are exposed to and their objective and subjective responses. This study will help to identify the extent to which individual variability affects responses to such chemical compounds commercially available, and determine whether objective and subjective responses of the participants are consistent with each other at various concentration levels.

Research Questions

The study is aimed to observe the objective and subjective responses to chemical exposure and draw relationships to the various concentration levels at which participants are exposed to:

1. How does the exposure to sub-limit concentrations of hydrocarbons impact objective and subjective measurements of sensory irritation?
2. How does the variation in concentration levels of hydrocarbon exposed to impact participants’ response?
3. What are the long term health impacts caused due to the prolonged exposure to industrial hydrocarbons?

Literature Review

The literature and studies discussed in this section provides the foundation for the proposed research study. The following section will address the issues associated with the existing permissible exposure limits and sensory irritation models before introducing the proposed models and methodologies.

Permissible Exposure Limits

Nowadays quality and safety controls play a prominent role within any industries. However, a huge number of employees employed in the production sectors experience sensory irritations and other chemical exposure symptoms such as headaches, persistent cough and seizures at concentration levels considered to be non-toxic and sub-irritant. OSHA has played a significant role in providing safe working conditions for the employees and has arranged various meetings with stakeholders to prevent occupational illness related to chemical exposure in the workplace (United States Department of Labor, 2014, para. 1).

One of the arguments made in such a meeting was to update the exiting permissible exposure limits (PELs) due to the fact that most of these limits defined in the past are outdated and obsolete and moreover, many of the present day chemical compounds are not listed within them (United States Department of Labor, 2014, para. 2). As a result OSHA is committed to put forward innovative and modified strategies and approaches that are required to handle the issue at hand and provide a safe working environment for the employees (United States Department of Labor, 2014, para. 3).

The permissible exposure limits developed by OSHA assumes that all employees exposed to chemical concentration levels at or below the prescribed limit will not experience adverse health conditions. However, a study conducted provides evidence that workers suffer chemical exposure symptoms even at chemical concentration levels below the prescribed limits. One such example is the 2-ethylhexanol. According to the American Conference of Governmental Industrial Hygienists (ACGIH) The prescribed upper limit for 2-ethylhexanol was 50ppm. However, from re-evaluation it was found that workers suffered sensory irritations below this limit. Therefore, this study points out how dangerous the current situation is and that many of the permissible exposure limits regulated by OSHA fails to protect employees from hazardous health conditions.

Sensory Irritation and Health Impacts

Sensory irritation is caused when allergic or harmful chemical compounds come in contact with skin or when it is inhaled. It causes irritation and discomfort to the trigeminal nerves and senses present in the mucous membrane of eyes, nose and upper respiratory tract. Brüning et al. (2014) recommends to apply sensory irritation as an endpoint whenever applicable to develop suitable permissible exposure limits to prevent hazardous working conditions.

From further studies and compilation of toxicological profiles of commonly used chemicals researchers came to the conclusion that sensory irritation can be considered as an important and crucial factor to assess risk to occupational hazards (Brüning et al. 2014). However, only 40% of the existing permissible exposure limits are based on the sensory irritation factor (Gaffney and Paustenbach, 2007). And according to Gaffney and Paustenbach none of the regulatory bodies around the world set any permissible exposure limits at levels non-detectable by the senses.

In the existing scenario, permissible exposure limits are obtained from animal models rather than human models, due to the lack of data collected from human models. In a study conducted it was made clear that tissue irritation is considered as an endpoint rather than sensory irritation (Brüning et al., 2014). Tissue irritations occur at higher concentrations and at faster pace, whereas, sensory irritation takes place at lower levels of concentration and at a slow pace. The sensory irritations perceived in the trigeminal nerves causes burning and tingling feelings in the olfactory senses. These effects may seem to be mild and reversible in the initial stages, but they have the potential to “become an adverse health effect due to the cascade of physiological defense mechanisms and finally tissue damage” (Brüning et al., 2014, p. 1866). As a result applying sensory irritation as an endpoint results in formulating an enhanced model which can reduce the chemical exposure symptoms that the employees face today.

Hydrocarbons in its natural state are mostly harmless to human beings. However, in the presence of sunlight or nitrogen oxides, these hydrocarbon undergo certain chemical reaction to form photochemical oxidants leading to photochemical smog. When these chemical reagents come in contact with skin or other organs, they cause certain sensory irritations. In extreme cases, such as ingestion or inhaling such chemical compounds lead to cyanosis, persistent coughing and other obstructive pulmonary ailments. If this situation is continued without providing necessary medical aid, it might even lead to certain neurologic symptoms such as drowsiness, poor coordination, stupor or coma and even seizures (Holtz, Tschopp, Soderstrom, Boillat, & Gutzwiller, 1992).

Current Models

The current literature addresses the issue at hand by stressing on the importance of utilizing sensory irritation as an endpoint and implementing chemosensory effects when prescribing permissible exposure limits. However, according to studies no methodological suggestions have yet been made for the procedures (Bolt, Triebig, and van Thriel, 2005). Characterizing organic compounds based on their chemical properties are of utmost importance as they affect the data on acute exposure in workplace (Blaszkewicz et al., 2005).

The exiting models lack accuracy as demonstrated by the variation in sensory irritation thresholds discussed in the literature. Moreover, the participant’s responses to chemical compounds are at time misdiagnosed due to the application of inadequate sensory irritation models (Blaszkewicz et al., 2005). And according to Blaszkewicz et al. (2005) some of the models obtain the irritation thresholds of certain chemicals by examining several other chemical compounds in conjunction with it, this again creates certain extrapolation errors in the model.

A technique that has been used in the existing models is the lateralization, which requires the participant to take short sniffs of chemical gases at sub-limit concentrations. This technique takes into consideration that sensory irritation can be localized to the side of the stimulated nostril. However, this end point is a high sensory measure and fails to take into consideration the sensory irritation symptoms that occur at low exposure rates. Moreover, the duration of chemical exposure in these techniques cannot be compared to that of an industrial environment (Blaszkewicz et al., 2005).

A large number of existing models make use of the data from animal studies and thus leads to inaccurate results. These inaccuracies result from the “differences in the species – difference in organs and neural mechanisms (e.g. receptors, immune defense, inflammation processes)” (Blaszkewicz et al., 2005, p. 532). The differences in the breathing patterns and biochemistry of the upper respiratory track in humans and rodents arises another prominent issue. As these data from animal model is used to derive guidelines for human models, significant adjustment must be made to accommodate the biological differences mentioned above (Dalton, 2002). In addition, Brüning et al. (2014), mentions that eye sensitiveness for animals differ from human beings and thus it is nearly impossible to extrapolate the results obtained from animal models to obtain a model suitable for human beings. Gaffney and Paustenbach advises that the quick and inexpensive animal models should only be implemented to prescribe preliminary permissible exposure limits only when there is a shortage in human data.

According to Dalton (2002) animal models have played a significant role in assessing sensory irritation in the past, however the significance in determining sensory irritation responses from human models cannot be downplayed. Hence, the author states that “the availability of safe, non-invasive assays to measure odor and irritant responses in the species of interest, humans, can both simplify and improve accuracy in the process of developing appropriate occupational exposure guidelines” (Dalton, 2002, p. 289). Other factors that reduce the applicability of current models to the industrial environment are time and pattern of exposure. Most of the human models that are implemented usually expose participants to chemical compounds for a short period of time (Blaszkewicz et al., 2005). As a result significant modifications need to be made to design a model that is well suited for the regular work shifts followed in workplaces.

Importance of Objective Measures

Objective measures are usually applied to reduce or minimize the biases that occur from subjective measures. Various methodologies used to assess objectively the sensory irritation such as “conjunctival redness, blinking frequency, nasal resistance and flow, pulmonary function, and reaction times” (Lang, Bruckner & Triebig, 2008, p. 24) are mentioned in the literature. Objective measures play a significant role in assessing sensory irritation, as a result prescribing permissible exposure limits without them makes the whole process strenuous. Since preconceived beliefs and prejudices are absent in symptoms such as congestion in the respiratory track and redness of the eye, objective methodologies such as nasal congestion and ocular photography are highly effective and yields accurate results.

The objective methodologies mentioned previously cannot be used to replace one another, since each of these methods are specific to a certain organ or biological system. This in turn increases the cost of the whole procedure. In addition, many of these methods are obstructive to the natural flow of process in an industrial environment, as a result it is inconvenient to employ them in a standardized sampling procedure. The researchers utilized eye blinks as an objective end point of sensory irritation caused to the eyes. In addition, they also concluded that persistent coughing is another symptom of sensory irritation. As a result, researchers also utilized the frequency of coughing as another end point of sensory irritation.

Eye blinks are responsible for lubricating the eye pupil. As a result, it can be deducted that the frequency in eye blinks are impacted by the dryness or irritation caused due to chemical exposure. One of the eye blink models designed was to observe the levels of eye irritation towards a hydrocarbon, namely 2-ethylhexanol at concentration levels below the permissible exposure limits. The results from this model indicated high levels of eye irritation, thus proving that the previous models were inadequate. The utilization of eye blink model hence was concluded to be a reliable source of objective measure (Blaszkewicz et al., 2005). In addition, researchers also concluded that persistent coughing is due to the irritation caused in the upper respiratory track due to chemical exposure. A cough model was designed to observe the frequency of cough when expose to formaldehyde at sub-limit concentrations. Again the results from this signified that previous models were inadequate. The utilization of cough model hence was concluded to be a reliable source of objective measure too (Lang et al., 2008).

Despite the reliability of these objective measures, the sensory irritation reported at low levels of concentration could not be measures by these methods (Dalton, 2002).  Such an example is seen in the cough model assessing throat irritations caused by the exposure to formaldehyde (Lang et al., 2008). For a low level concentration ranging from 0 ppm to 0.3 ppm, subjective measurements experienced a significant increase. However, the objective measures of throat irritation deviated from the subjective measurement results. At concentrations of 0.5 ppm with 1 ppm peak exposure, the objective measures showed a slight increase. When correlating objective measures with subjective, it was found that the relationship was slightly positive. The authors came to the conclusion that the discrepancies in objective and subjective measurements were a result of biased and other personality factors (Lang et al., 2008).

As concluded by the researchers, objective measures alone cannot account for all the sensory irritations experienced by an individual. According to Dalton (2002), “Subjective reports of irritation at low levels that cannot be reconciled with objective measures should prompt a careful investigation into the other factors (e.g., cognitive or emotional) that may be modulating the sensory response” (p. 284). As a result, it can be concluded that a relationship exists between the concentration levels of a chemical and a participant’s perception of the concentration levels. In addition, the author also explains that the small objective change in the mucous membrane of the upper respiratory track may not cause employees any sensory irritation. Therefore, it is strenuous to create a model that protects employees from any sensory irritation, due to the discrepancies in the objective and subjective measurements. As a result, combing objective and subjective measures may yield an enhanced knowledge regarding the sensory irritation mechanisms and individual variability (Dalton, 2002).

Importance of Subjective Measures

Although objective measurements are the prime candidates for setting permissible exposure limits, it is important that the regulatory limits in a workplace should not avoid subjective measurements despite the challenges they present (Bottai & Ernstgarda, 2012). This is proved through an experiment where perceived health impacts of n-butanol, an organic compound was studied (Andersson, Claeson, Ledin, Wisting & Nordin, 2013). The study exposed the response to low level chemical exposures, which are based on predisposed traits of the participants. Those with a negative bias towards chemical exposure did not adapt to the experiment over time. Moreover, these participants performed worse than the low distress group in cognitive tasks and reported more sensory irritation symptoms over time. This study provides knowledge on the potential impacts perception and individual traits have on an individual’s response to chemical exposure, and gives further reason to why subjective measures need to be included in assessing exposure limits (Andersson et al., 2013).

As mentioned previously, sensory irritation caused by top-down processing arises from perceived risk, perception and past experiences (Dalton & Smeets, 2005). The personality trait associated with increased expectancy of illness reported more reporting of sensory irritations. An experiment obtained individual responses to chemical exposure and compared it on a high and low ends of a negative affectivity spectrum to study the subjective measures to chemical exposure. The results suggested that those individuals with high negative affectivity reported more sensory irritations than the rest (Dalton & Smeets, 2005).

In order to further observe the impacts of subjective measurements to chemical exposure Andersson et al. (2016) conducts a Multiple Chemical Sensitivity test (MCS). Multiple Chemical Sensitivity, is a symptom that causes individuals to react to everyday chemical exposures at very low concentration levels. This experiment exposed individuals with MSC and healthy control groups to n-butanol, a hydrocarbon at low concentration levels above the odor threshold. Participants suffering from MSC reported more symptoms of sensory irritations over the course of the experiment when compared to the healthy control groups. This may have caused as a result of sensitization to the chemical compounds over time. In addition, the participants with MSC also exhibited higher pulse rates and also reported higher odor intensities throughout the course of the experiment. This study signifies on the importance of how responses of individuals suffering from certain conditions such as MSC are different from the common response. Thus such medical conditions also need to be taken into account while assessing subjective measurements.

Ernstgrad and Bottai (2012) explored ways to measure subjective responses. One such method made use of a visual analogue scale (VAS) to find out whether subjective measurements could be validated by objective measurements. In this study, researchers utilized nine different chemical compounds, and reported objective and subjective measurements of sensory irritation to eyes, nose and throat. Although the study did not yield an overall strong relationship between the objective and subjective measures, there was a significant correlation between the two measurements at low chemical concentrations. As a result, the researcher concluded that the results indicated a potential positive relationship between objective and subjective measurements, and deemed the VAS as a useful technique for analyzing sensory irritation subjectively in chemical exposure studies (Bottai & Ernstgard, 2012).

From the above mentioned studies it can be concluded that subjective measurement demonstrates an important factor while designing models with permissible exposure limits to chemical exposure. However, it is unreasonable and impractical to set permissible exposure limits at concentration levels below both odor and sensory irritation thresholds (Gaffney & Paustenbach, 2007). It would be easier to educate employees the actual health impacts caused due to prolonged chemical exposure and ease their concern regarding minimal exposure to chemicals commonly used in workplaces (Gaffney & Paustenbach, 2007). Moreover, as these studies imply it is a strenuous and time consuming procedure to validate subjective measurements and compare it with objective measurements (Ernstgard & Bottai, 2012).

Proposed Methodologies

Several models were proposed to address the issue at hand, however due to the complexity of developing permissible exposure limits most of these models have been rejected. The differences in the sensory irritations between animals and human beings have been proposed by Brüning et al. (2013). However it lead to inadequate results due to the inaccuracy in extrapolation. Researchers concluded that the study could be carried out with human exposure data and animal data with an interspecies extrapolation factor of 3. This factor could be used to extrapolate the identified sensory irritations in animals to human beings. The validity of such factors was confirmed by experimenting with hydrocarbons such as 2-ethylhexanol. Although, if the chemical compound was an irritant, more toxicological information and epidemiological data is required for the assessment. And if the data provided is unsatisfactory, the chemical compound needs to be analyzed on a case-by-case basis. A limitation of using animal models is that it is impossible to observe and analyze animal perception to odor. In addition, individual variability needs to be accounted too (Brüning et al. 2013). Subjective measurements are difficult to develop and the lack of subjective measures limits the scope of the study.

Another approach that utilizes mathematical calculations of permissible exposure limits for hydrocarbons based on its chemical composition was proposed (Daughtrey, McKee, and Medeiros, 2005). The values obtained from these calculations are based on acute central nervous system depression and sensory irritation of the eyes and upper respiratory system (Daughtrey et al., 2005). Czerczak and Jakubowski (2010) proposed a methodology to improve this model based on mathematical equations. Exposure limits for volatile organic compounds can be obtained in the absence of human data by calculating nasal pungency threshold based on their odor properties. However, this approach cannot be extended to study reactive volatile organic compounds (Czerczack & Jakbowski, 2010). In addition, this methodology relies on compositional information rather than human data, therefore it limits the scope of study.

Gaffney and Paustenbach (2007) proposed a model where chemicals were classified into three categories based on the concentration levels at which they cause sensory irritations. Most of the chemicals belonged to Model II which had an odor threshold below sensory irritation threshold. If the odor was unpleasant, the permissible exposure limits were set below odor thresholds. And if this was not possible, the exposure limits were set below a particular percentage of the population’s odor threshold and below sensory irritation threshold.

The literature further needs to understand how sensory irritation differs among individuals by utilizing human data. Dalton and Smeets (2005) recommended using a model that combined the objective and subjective measures when prescribing permissible exposure limits through the use of participant ratings. Likert scales can be implemented to obtain knowledge about how perceived symptoms and intensity vary among individuals. In addition, Dalton and Smeets (2005) suggests that the issue can be further understood by establishing a relationship between the objective and subjective measures.

Methodology

In order to study the impact of hydrocarbon exposure on objective and subjective measures of sensory irritations, a quantitative research design with an experimental strategy of inquiry will be utilized. An experimental research is applicable in this study since it attempts to determine if a treatment influences an outcome. In this proposed study, Hydrocarbon exposure is the treatment while the objective and subjective measurements of sensory irritation are the outcomes. A pre-experimental design is utilized due to the fact that one group will receive the treatment interventions without the use of a control group. This is applicable because same group of participants will be used throughout the experiment to minimize error dude to bias.

Participants

The target population for this experimental study is the employees in the production sector at Bayway Refinery located in Linden, NJ. The employees in this refinery come in contact with hydrocarbons on a daily basis. Based on a population size of 800 production employees total over three shifts and a desired confidence interval of 95%, a sample size of 80 participants will be selected through random selection procedures. The participants will be chosen from workers who are regularly exposed to hydrocarbon products and employees who have less interaction with hydrocarbon compounds. Participants who volunteered will be selected as the group from which the sample size is chosen randomly. In order for the employees to participate in this experimental study, they need to undergo a preliminary health test, to make sure that they can be exposed to sub-limit concentrations of hydrocarbon for a prolonged period of time. In addition, the participants will be awarded with a 25 dollar gift voucher for their participation.

Measurement Instruments

The experiment is carried out at three different concentration levels of hydrocarbon, and the concentration within the exposure chamber will be altered by mixing hydrocarbon vapors with ambient air. Appropriate valve and piping systems will be used to control the flow of hydrocarbon vapors into the exposure chamber. A gas chromatograph will be utilized to monitor the concentration within the exposure chamber throughout the duration of the experiment.

In order to measure eye irritation responses objectively, electro-encephalography electrodes (EEG) will be used (Blaszkewicz et al., 2005). The electrodes are placed next to the eyes and eye blinks are recorded electro-physiologically and stored in a data storage. Portable tape recorders with dynamic microphones will be used to record coughs and measure its severity (Lang, Bruckner & Triebig, 2008). In addition, subjective measures will be obtained by using a six-point Likert scale rating prevalence of eye and throat irritation using the following options: 0=not at all, 1=slight, 2=somewhat, 3=moderate, 4=strong and 5=very strong. The eye irritation will include symptoms such as tiring, itchy, dryness, burning, and watery eyes as mentioned by Bruckner et al. (2007).

Procedure

As mentioned previously the participants will be exposed to three different concentrations of hydrocarbon on three separate days and each exposure time period will last for three hours. In order to minimize the overall time taken for the experiment, the sample size of 80 participants will be divided into four sections of 20 participants each. These experimental procedure will last for four weeks, and each group of participants will be observed each week from Monday to Wednesday. Ten participants will be observed in the mornings, and ten participants will be observed in the afternoons.

The concentration levels exposed to will be below regulatory limit to protect participants and assess sub-limit impacts. These concentrations will include 5, 10 and 20 ppm. Peak exposures will occur in an interval of thirty minutes over the three hour time period. This approach was selected to make the simulation as realistic as possible. In order to control other external noise factors, temperature, pressure, and humidity in the exposure room will be controlled. Likert scales will be used to obtain subjective measure before the exposure to avoid pre-exiting sensory irritations. And a posttest will be carried out to determine subjective responses to exposure. Eye blinks will be measured before exposure and this reading will be used as the baseline reading. Eye blink readings will be measured again following the three hour exposure period. The change in the eye blink frequency can be deduced from these readings and objective measurements can be developed. Moreover, coughs will be recorded using tape recorders and microphones which too is utilized to obtain objective measures. The severity of coughs will be used to judge the ailments that the respiratory system might contract. Finally, a Likert scale will be provided for the participants to provide their subjective response regarding nasal and throat irritations caused during and after exposure.

Limitations

This study which is carried out to obtain relationship between hydrocarbon exposure and objective and subjective measures provide knowledge and shed light over the deficiencies that the past models had, however it too face certain limitations. Firstly, the experiment will only select participants that pass a health check-up. Therefore, these findings cannot be applied to the percentage of population that does not meet the health criteria. Secondly, the experiment will be conducted over a time frame of three hours which is less than half the duration of a normal work shift. As a result these results obtained might not be practically relevant to an industrial working condition. Another limitation to the study is that it only applies to employees at the Bayway Refinery, and as a result further research is required to generalize the results to the entire workforce in the production sectors. Another limitation is the cost and time taken to carry out the experiment. Usage of sophisticated instruments increases the budget of the study. And finally the instrumental errors may reduce the accuracy of the results.

Data Analysis

Descriptive statistics will be employed to analyze the difference in the responses at different concentration levels. The result from these descriptive statistics will be used to assess the impact of various concentrations of hydrocarbon exposure on objective and subjective responses. The change in mean, median and mode obtained from the eye blink frequency will be reported for each concentration levels of hydrocarbon. Inferential statistics, such as ANOVA, will be used to determine if significant differences exist between the mean obtained from the eye blink data for three different concentration levels. Through these procedures, research question on regarding the impact of sub-limit concentrations of hydrocarbon on objective responses can be answered. The same analysis methodology will be employed for the subjective measures determined at each concentration levels. The mean and median subjective ratings will be reported for each exposure concentration levels, and ANOVA tests will be carried out utilizing the means to determine if any significant difference exists between the various concentrations levels. Medians will be reported in conjunction with the means due to the fact that the statistic is not impacted by outliers.

The difference in the mean, median and mode of the data gathered for three different concentration levels will be used to provide descriptive statistics to determine the impact of variation in concentration levels on the participants’ response. The results from these statistics answer the second research question. Linear regression is used to determine the relationship between objective and subjective measurements. Scatterplot will be used to represent the relationship between objective and subjective measurements.

Finally the measurements from tape recorders and microphones will be used to judge the severity of nasal and throat irritation to the exposure of hydrocarbons. The results from the Likert scale coupled with the results from the tape recorders and microphones can be used to determine the long term health impacts caused due to the prolonged exposure to industrial hydrocarbon. And by prescribing a suitable sub-limit condition for hydrocarbon exposure, majority of these adverse health conditions can be averted.

Conclusion

The protection of employee within the workplace from hazardous working conditions is becoming increasingly important nowadays. At this point in time, OSHA needs to ensure that workers are being adequately protected from chemical exposures by utilizing the permissible exposure limits. With outdated and obsolete limits and a lack of adequate models to assess sensory irritation for both existing and new chemicals, there is a need for research to address the situation at hand. This includes utilizing human participants rather than animals in order to increase relevance and avoid individual variability. Organic compound sensory models are considerably deficient and in need of attention. The literature notes the importance of assessing these chemicals objectively as well as subjectively.

This research proposal seeks to establish a further understanding of the relationship between chemical exposure, objective and subjective responses. Increased understanding of the relation between these variables will enable the development of enhanced sensory irritation models for organic compounds such as hydrocarbon. In addition, these models will be able to protect a larger percentage of the workforce in the production sectors from symptoms caused by bottom-up and top-down processing. The research will also provide insight into the sufficiency of the permissible exposure limit for hydrocarbon and reassess its sensory irritation potential. Sensory irritation is a sensitive endpoint, and as a result is very important to consider when assessing and developing exposure limits. Furthermore these experimental models proposed will minimize the symptoms of sensory irritation and in the long run counteract the hazardous health conditions that existed due to the deficiencies in the previous models. In summation, this research will seek to provide further insight into how sensory irritation models can be improved to protect employee well-being.

References

American Industrial Hygiene Association (2002). Permissible Exposure Limits (PELs). Retrieved from https://www.aiha.org/government-affairs/WhitePapers/whitepaper02_PELs.pdf

The American Industrial Hygiene Association (AIHA) developed this white paper to address the need for the Occupational Safety and Health Administration to update the permissible exposure limits to chemical exposure. Everyday new toxicity information on chemicals are developed, and thus the AIHA recommends that OSHA work with stakeholders to adapt these information to update the current exposure limits. The employers are called upon to safeguard their employees from chemical exposure through adequately assessing hazardous chemicals in the workplace. This white paper aids this research by calling upon stakeholders to aid the process of updating exposure limits based on the current scientific information available. Employers can utilize these information provided in the literature to address chemical hazards within their own industrial environment.

Andersson, L., Claeson, A., Dantoft, T. M., Skovbjerg, S., Lind, N., Nordin, S., & Högskolan i Gävle. (2016). Chemosensory perception, symptoms and autonomic responses during chemical exposure in multiple chemical sensitivity. International Archives of Occupational and Environmental Health, 89(1), 79-88. doi:10.1007/s00420-015-1053-y

This study addresses how individuals suffering from Multiple Chemical Sensitivity (MCS) respond to low concentration chemical exposure in comparison to healthy controls. The results revealed that possessing this trait led to an increase in symptoms reported, higher pulse rates, and stronger perceived odor when compared to the results of the controls. The research sheds light on the potential effects of individual variability can have on reaction to chemical exposures.

Andersson, L., Claeson, A., Ledin, L., Wisting, F., & Nordin, S. (2013). The influence of health-risk perception and distress on reactions to low-level chemical exposure. Frontiers in Psychology, 4, 1-8. doi:10.3389/fpsyg.2013.00816

The objective of this research is to examine how health-risk perception and personality factors influence ones response to chemical exposure in regards to intensity of odor, reported symptoms, and cognitive performance. The participants were divided into high and low distress groups, and bias was manipulated by providing negative information regarding the chemical compound to certain participants and positive information to other participants. The study found that high distress individuals reported more symptoms, performed worse on cognitive tasks, and rated the exposure as more disagreeable than compared to the low distress individuals. This study provides insight into how subjective factors can influence an individual’s response to chemical exposures.

Blaszkewicz, M., Kiesswetter, E., Thriel, C. V., Schäper, M., & Seeber, A. (2005). Eye blinks as indicator for sensory irritation during constant and peak exposures to 2- ethylhexanol. Environmental Toxicology and Pharmacology, 19(3), 531-541. doi:10.1016/j.etap.2004.12.056

This research explores the use of eye blinks as a reliable objective measure of sensory irritation, and re-evaluates the sensory irritation potential of 2-ethylhexanol in individuals over time. The results of the research indicate a strong dose-response relationship between blink frequency and volatized chemical compound exposure over time. In regards to the current exposure limit, the research revealed the potential sensory irritation of 2-ethylhexanol is higher than anticipated. This study gives further evidence signifying the need to update exposure limits based on sensory irritation, and also potential opportunities to explore irritation objectively with the use of electro-physical eye blink recordings.

Bolt, H. M., Triebig, G., & van Thriel, C. (2006). Editorial: Evaluation of chemosensory effects due to occupational exposures. International Archives of Occupational and Environmental Health, 79(4), 265-267. doi:10.1007/s00420-005-0058-3

This article addresses the need to assess chemosensory effects of chemicals when developing occupational exposure limits. Researchers are working on reviewing methods to assess the sensory irritation properties of volatile organic compounds and their effects on human beings. The authors discuss how utilizing human exposure studies is becoming increasingly important in this research, as well as address the issues associated with animal models and short duration human studies.

Brüning, T., Bartsch, R., Bolt, H. M., Desel, H., Drexler, H., Gundert-Remy, U., & van Thriel, C. (2014). Sensory irritation as a basis for setting occupational exposure limits. Archives of Toxicology, 88(10), 1855-1879. doi:10.1007/s00204-014-1346-z

The journal article discusses the need to incorporate sensory irritattion information into the process for setting exposure limits. The researchers discuss a conceptual model for the occurrence of sensory irritation through either a sensory irritation or a tissue irritation pathway. Through the use of available human and animal data, the authors derived an extrapolation factor that can be utilized to account for interspecies differences in sensory irritation. The authors provide this methodology to improve the derivation of exposure limits for chemicals lacking sufficient human data on sensory irritation.

Dalton, P. (2002). Odor, irritation and perception of health risk. International Archives of Occupational and Environmental Health, 75(5), 283-290. doi:10.1007/s00420-002-0312- x

The researcher addresses the lack of reliable irritation models for volatile organic compounds, as well as failure to take non-sensory factors into account when assessing these chemicals. The article approaches the issue associated with distinguishing sensations of odor from sensory irritation, as well as psychophysical methods for assessing sensory irritants. The author discusses the importance of accounting personality variables and preconceived beliefs when assessing irritation due to the significant impact these factors can have on an individual’s response to chemical exposure. The article emphasizes the need to measure and account for both objective and subjective responses when developing occupational exposure limits, as well as the need to continue conducting developing human models rather than animal models.

Dalton, P. H., & Smeets, M. A. M. (2005). Evaluating the human response to chemicals: Odor, irritation and non-sensory factors. Environmental Toxicology and Pharmacology, 19(3), 581-588. doi:10.1016/j.etap.2004.12.023

The authors explain how sensory irritation occurs within individuals through the information-processing model. This includes bottom-up processing where irritation is caused by a stimulant within the environment, as well as top-down processing where irritation is caused by cognitive factors. Further support for understanding objective and subjective responses to chemical exposures is provided within this article. The implication this model may have in setting occupational exposure limits is explored.

Ernstgård, L., & Bottai, M. (2012). Visual analogue scales: How can we interpret them in experimental studies of irritation in the eyes, nose, throat and airways? Journal of Applied Toxicology, 32(10), 777-782. doi:10.1002/jat.1681

This journal article investigates the validity of utilizing visual analogue scales to measure irritation. The researchers provide evidence that objective and subjective measures are correlated in regards to respiratory and eye irritation. This finding indicates the validity of utilizing subjective scales to assess sensory irritation in exposure studies.

Gaffney, S., & Paustenbach, D. (2007). A proposed approach for setting occupational exposure limits for sensory irritants based on chemosensory models. Annals of Occupational Hygiene, 51(4), 345-356. Retrieved from https://ill.rit.edu/ILLiad/illiad.dll?Action=10&Form=75&Value=292845

The researchers address the issues associated with setting occupational exposure limits for irritating and odorous chemicals. A methodology is proposed to tackle this issue through dividing chemicals into three groups based on their odorous properties. Based on the category, a particular pathway is suggested for developing exposure limits. The model takes risk perception and individual variability into account in order to ensure a particular percentage of the population is protected from sensory irritation based on feasibility. The researchers call for an agreeance on the end points exposure limits should seek to protect employees from, such as eye irritation, as well as a need for human data to increase the viability of the methodology.

Hotz, P., Tschopp, A., Soderstrom, D., Holtz, J., Boillant, M., & Gutzwiller, F. (1992). Smell or taste disturbances, neurological symptoms, and hydrocarbon exposure. International Archives of Occupational and Environmental Health, 63(8), 525-530.

A cross-sectional study concerning the toxicity of hydrocarbons is carried out in this study. A clinical examination shows an increased prevalence of smell and/or taste disturbances in the heavily exposed group. These symptoms appear to be generally transitory and reversible and they seem to be due to concentration peaks rather due to long exposure durations. They are associated with acute depressor effects and not with symptoms which could belong to a hydrocarbon induced chronic toxic encephalopathy.

Lang, I., Bruckner, T., & Triebig, G. (2008). Formaldehyde and chemosensory irritation in humans: A controlled human exposure study. Regulatory Toxicology and Pharmacology, 50(1), 23-36. doi:10.1016/j.yrtph.2007.08.012

This research explores the subjective responses and sensory irritation observed in human beings exposed to formaldehyde at concentrations relatable to the occupational environment. The study observed the impact of the chemical on eye, nose, and lung irritation through the use of objective and subjective measures. There was no strong positive correlation between the objective and subjective results for any form of irritation. The study offers further insight into the discrepancies that can exist between subjective experiences and observed signs of sensory irritation.

McKee, R. H., Medeiros, A. M., & Daughtrey, W. C. (2005). A proposed methodology for setting occupational exposure limits for hydrocarbon solvents. Journal of Occupational and Environmental Hygiene, 2(10), 524.

The authors explore the complexities associated with determining occupational exposure limits for hydrocarbon, and propose an approach to tackle this issue. This includes grouping solvents together based on their compositional properties and utilizing a reciprocal calculation procedure to determine guidance values. This approach addresses eye and respiratory tract irritation as the most sensitive endpoint. The study provides another methodology to improving occupational exposure limits based on sensory irritation.

Shusterman, D., Matovinovic, E., & Salmon, A. (2006). Does haber’s law apply to human sensory irritation? Inhalation Toxicology, 18(7), 457-471. doi:10.1080/08958370600602322

The authors address utilizing sensory irritation as an end point when assessing chemical exposures. It addresses the need to model sensory irritation based on physical chemistry of the substances, as well as in terms of concentration and duration. The authors suggest that, as indicated by Haber’s Law, low level exposures over an extended period of time may be equivalent to short high level exposures. The study provides evidence of the need to study exposures as they relate to time and concentration rather than relying on short studies.

United States Department of Labor. (2014, October 14).OSHA launches national dialogue on  hazardous chemical exposures and permissible exposure limits in the workplace [Press Release]. Retrieved from https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=NEWS_RELEAS ES&p_id=26841

This news release calls for a conversation with stakeholders on the need to improve exposure limits in their workplace. It addresses the fact that OSHA’s exposure limits inadequately protect workers and are 30 years out of date. The dialogue suggests that researcher, chemical manufacturers, employers, and any party concerned with the health of workers step up to aid the agency in determining approaches to resolve the issue. This dialogue provides reason to research the impacts of sub-limit chemical exposure that may be harming employees.

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