Protective Clothing and Respiratory Protection 7-1
Private Stored Grain Fumigation Manual
Protective Clothing and Respiratory Protection In This Chapter Protective Clothing Cleaning Clothing Used During Application Respiratory Protection Time Weighted Averages Short-Term Exposure Limits Amount of Time Masks Can Be Used Sealing of Masks
Protective Clothing and Respiratory Protection
Protective Clothing and Respiratory Protection 7-3
Part II, Chapter 7: PROTECTIVE CLOTHING AND RESPIRATORY PROTECTION
Learning Objectives: ♦ Know what gloves to use with phosphine. ♦ Know whether clothing used during fumigation should be laundered or dry-cleaned. ♦ List the two types of respiratory protection that are worn during fumigation. Describe when they should be used. ♦ Be able to calculate the Time Weighted Average (TWA) for exposure to fumigants, know what a STEL is and how to calculate it. ♦ List three types of gas detection devices, how they are used, and what their advantages and disadvantages are. ♦ Know what respiratory protective gear must be on-site for fumigation and where it should be located. It is confusing for most people to understand the differences between the safety equipment needed for handling various restricted use pesticides. Most farmers know how toxic pesticides can be and they usually take care to use every piece of protective equipment available when mixing their loads and out in the field when cleaning a plugged nozzle. But this same equipment that protects the applicator when handling pesticides for field application could seriously injure or even kill the applicator of fumigants. Since fumigants are pesticides in the form of gases, they act differently than pesticides in the liquid form. When the gases are given off, they fill the entire volume of a structure and come in contact not only with the clothing, skin, and eyes, but will quickly enter the lungs and blood stream if they are inhaled. Some of this cannot be helped, but the level of this contact can be monitored and safety judgments and actions can be taken to minimize the dangers of poisoning for the applicator. This chapter will focus briefly on the clothing to be worn while applying phosphine and the respiratory protection that must be worn when the thresholds of phosphine gas have been reached.
Protective Clothing The statements made about protective clothing on most phosphine labels are at most only a couple of sentences long. Generally they tell the applicator to use dry cotton gloves and loose-fitting cotton clothing that breathes. These
Since fumigants are pesticides in the form of gases, they act differently than pesticides in the liquid form.
Protective Clothing and Respiratory Protection
precautions are meant to guide the applicator in the right direction by leaving the typical pesticide protective gear alone. The reason for this is that most protective gear, whether it is gloves, aprons, goggles, or suits, is designed to keep liquid pesticides out. But this gear is as effective in trapping air inside as it is in keeping pesticides outside, and that is a serious problem when it comes to fumigants.
Even a wedding ring can trap enough dust and gas to create a burn.
Phosphine dusts and gas can severely burn if they are trapped against the skin and not blown away by the natural air currents that body movement makes. Part II, Chapter 5 of this manual pointed out that even a wedding ring can trap enough dust and gas to create a burn. So trapped gases and dust are not something that should be taken lightly. The best way to avoid trapping phosphine gas or dust against the skin is to wear clothing that allows for maximum movement of air and breathability. This means that the rubber gloves should be exchanged for cotton work gloves, and the protective suits should be exchanged for loose-fitting jeans and a t-shirt or long-sleeved cotton shirt. The cotton gloves protect the hands from dust that can heat up when it comes in contact with the sweat on a workers hands, and the loosefitting cotton clothing allows gas to move about the body and not be trapped.
These are several points to remember when choosing clothing for fumigating and when washing up afterwards: •
Make sure all clothes and gloves will breathe.
Empty pockets before fumigating. Anything you carry may be contaminated during fumigation.
Remove all Bandaids® or bandages before fumigating, or do not fumigate with an injury that requires them. The fumigant dust or gas can get under the bandage and severely burn the skin.
After fumigating and before laundering, inspect all metal on the clothing. Phosphine gas can corrode snaps, zippers, rivets, and buttons that have a metal edging. If these things are corroded, it may be best to simply throw the clothing away rather than go to the effort of carefully aerating and washing it.
DO NOT WEAR COVERALLS OR OVERALLS! Even if they are made of cotton, coveralls and overalls tend to trap air inside and against the skin.
Always hang clothes outside that were used during fumigating and allow them to fully aerate before laundering. Never dry-clean clothes used for fumigating.
If clothing is very dusty, shake out as much dust as possible, and after aerating, wash items two or three times and hang them to dry in the sun.
Use hot water for washing (146°F).
Protective Clothing and Respiratory Protection 7-5
Clean the washing machine by running it without clothes for a complete cycle with detergent. This insures that no fumigant will contaminate other clothing.
Wash fumigating clothes by themselves and not with other work clothes.
Respiratory Protection During fumigation, the single most important thing to keep in mind is your air supply. By far, most fumigating injuries and deaths occur from inhalation of the phosphine gas. Compared to other fumigant gases, phosphine is more easily handled for two reasons. First, the gas given off by aluminum or magnesium phosphide usually has a garlic odor that can warn the applicator about rising levels of the gas. Keep in mind that the garlic odor cannot always be relied upon to give a warning of elevated phosphine gas levels. And second, phosphine pellets and tablets take a number of minutes of exposure to air and humidity to begin giving off the hydrogen phosphine gas, often giving the applicator time to apply the fumigant and get out of the building. The first step in fumigation safety is to know what the levels of phosphine gas are so that choices can be made during the fumigation about the respiratory protection needed. There are several ways of doing this. Due to the high cost of external and internal air monitoring systems such as a Fumescope® or an infrared air monitor, the most common devices used are either a Draeger® Pump or a Draeger® Badge. The Draeger Pump uses disposable glass tubes that will change colors when air is drawn through them to indicate the current levels of phosphine gas. Tubes are available for many different types of gas detection, so make sure you do indeed have tubes for the detection of phosphine. Draeger pumps are highly effective and accurate when used properly. Their downside is that they will only give readings when the applicator takes the time to stop, put in a new glass tube, and take a monitoring sample. If you get busy and forget to take regular readings, gas levels can quickly creep up into the dangerous zone. A Draeger Badge, on the other hand, will constantly monitor the phosphine levels in the air and change colors when toxic levels have been reached. The downside of the Draeger Badge is that it is used only once, and after it has changed colors indicating an elevated phosphine level, you will have no idea about how high the levels have gotten, or which type of respirator you should be using. OSHA (Occupational Safety and Health Administration) and the EPA (Environmental Protection Agency) have determined certain exposure limits to phosphine gas for worker safety. Two terms describe these limits: TWA (Time Weighted Average) and STEL (Short-Term Exposure Limit). Basically, a TWA is the total exposure of a worker to phosphine gas over an 8-hour
Draeger pump with a gas detection tube attached.
Protective Clothing and Respiratory Protection
period, and a STEL is a 15-minute TWA that can be reached only 4 times in one day with at least an hour between each exposure. The TWA for phosphine is 0.3 ppm and the STEL is 1.0 ppm. To determine a TWA, the applicator must take several air monitoring samples during each fumigation. TWA = (C x T + C x T + C x T
) ÷ 8 hours, where C = the concentration of phosphine gas taken from the reading T = the time at this exposure Example: Calculate a TWA for phosphine exposure of 0.2 ppm for the first ½ hour, 0.5 ppm for the next ¾ of an hour, and 0 ppm for the rest of the 8-hour period. TWA = (0.2 ppm x ½ hour) + (0.5 ppm x ¾ of an hour) + (0 ppm x 6 ¾ hours) ÷ 8 hours TWA = (0.1 ppmh) + (0.375 ppmh) + (0 ppmh) ÷ 8 h
TWA = 0.059 ppm
4 pp .0 m
Gas detector tube showing a reading of 1.5 ppm. As you can see, the TWA limit of 0.3 ppm was not exceeded during this eighthour period, even though the limit of 0.3 ppm was exceeded for a brief time. Dont forget that when you calculate the TWA for a fumigation you must
Protective Clothing and Respiratory Protection 7-7
include the rest of the time in that 8-hour period at 0 ppm (Example: 0 ppm x 6 ¾ hours). Also remember that even though your TWA may remain under 0.3 ppm, you can never go above 1.0 ppm in any given 15-minute period or you will go over the STEL. TWA and STEL calculations are necessary to understand because the fumigation label uses them to describe phosphine limits and because they are necessary information for your record keeping. The STEL can be very useful for the applicator because it allows a brief period of time when the applicator can be exposed to limits up to 1.0 ppm, and this may sometimes happen during a phosphine application. But these calculations can be confusing. If you think you may make a mistake in your calculation, or if you do not know how long you will be exposed to phosphine gas in any given 8-hour period, then you should always follow the limit of 0.3 ppm and wear the appropriate mask or tank for your situation. The maximum limit of phosphine gas exposure without a respirator or mask is 0.3 ppm (parts per million). From 0.3 ppm to 15 ppm a canister gas mask designed for phosphine gas can be used. Above 15ppm a SCBA must be worn. If the levels of phosphine gas are not known, you are required to assume the worst possible situation and wear an SCBA. You are not required to have these masks on site during a fumigation, but it is a very good idea. It is necessary to have access to them if they are needed for reentry to the facility or if the fumigation will take a while and applicators will be exposed to high gas levels. For example, if a gas mask or air tank will not be needed during a phosphine fumigation, it is still necessary to have access to one or both through either the pesticide dealer or a local fire department. Make sure that this is arranged before a fumigation, so time isnt wasted locating this equipment if it becomes necessary. Facepiece Hood harness Eyepiece Directing air inlet tube Inhalation valve
Carrier harness neck strap
Exhalation valve Carrier harness body strap
Flexible, non-kinking tube Air-purifying element (canister)
Carrier harness case
Front-mounted canister-type respirator.
Protective Clothing and Respiratory Protection
The phosphine label says that a canister gas mask can be used to escape from a structure with phosphine gas levels between 15 ppm and 1500 ppm. But these masks are designed for very low levels of phosphine gas, so the emphasis must be on escape only and not ever for application purposes. These are the levels to keep in mind for gas masks and SCBAs: •
Up to 0.3 ppm - applications can be made without a respirator or mask
Between 0.3 ppm and 15 ppm - a phosphine canister gas mask must be worn
Above 15 ppm - an SCBA must be worn (An SCBA may be substituted with an approved air line system and mask. This system pumps air from the outside through a hose to a mask).
Beards and glasses interfere with the sealing of most masks.
When using a canister-type gas mask or a respirator, there are two things to keep in mind: time and sealing. Phosphine gas canisters have seals covering both the air intake and connecting threads that go to the mask. Once these seals are broken, the canister can only be used for the amount of time printed on the side. Some manufacturers handbooks for these canisters will allow for resealing of the canister or putting the canister in an airtight plastic bag for reuse at a later time. If this is the case, be sure to clearly mark on the canister with a permanent marker exactly how long the canister was exposed to air, not just how long it was used. It is also a good idea to date when the canister was used since some canisters have expiration dates. Always throw away canisters that have gone past their expiration dates, whether or not all of their useful time has been used. Air tanks on SCBAs contain only a certain amount of air. Make sure that all fumigation tasks can be completed with the amount of air inside the tank. You should calculate your time so that you can leave the structure before air runs out. Keep in mind that some peoples respiratory volume is greater than others and they will use air faster. Also, hotter conditions will increase the rate of respiration. Training on how to use and handle compressed air tanks is strongly advised before they are used in a fumigation.
Sealing In this case, sealing does not refer to the resealing of a gas mask canister or the sealing of a bin, but rather the seal that is created between the rubber of the mask and the face. Since hydrogen phosphine gas can enter the smallest cracks and crevices, it can also get into an improperly sealed mask and poison or severely burn the applicator. Make sure that the mask you choose fits your face shape and creates a tight seal. Sometimes this seal can be checked by fitting the mask to the face without the canister or tank. First cover the air
Protective Clothing and Respiratory Protection 7-9
intake or hose with your hand and breathe in. This will tighten the mask to the face. If air leaks in between the rubber seal and face skin, this is a poor fit and another mask should be found. Certain face shapes may not work with a mask, and this person should never fumigate whether or not a mask may be needed since an emergency reentry to the facility may require a mask. Beards and glasses interfere with the sealing of most masks. It is necessary to be clean-shaven on the day of fumigating and either go without glasses or use contact lenses.
References University of Illinois Extension Service. 1997. Illinois Pesticide Applicator Training Manual: Grain Facility Pest Control. Urbana, Illinois. Iowa State University, University Extension. 1998. Iowa Commercial Pesticide Applicator Manual: Fumigation, Category 7C. Ames, Iowa.