Chemical exposure at work.

Chemical exposure at work

Our industry is one that I define as "chemically intense." That is, we use significant quantities of many different chemicals in the manufacturing process. A great number of these chemicals react during normal processing forming a variety of new products and by-products.

In the last 20 years, our society has become much more aware of the potential hazards associated with chemicals. Many of the materials considered safe 20 or 30 years ago have been identified as serious health hazards and in many cases have been banned. Consider asbestos or PBNA. This poses a significant challenge for our industry. In order to continue to produce many of the products we make, we must continue to deal with chemicals and other materials that may be hazardous to us in the manufacturing process. At the same time we must have work areas that are safe for all who enter them.

Large companies and union organizations have conducted wide ranging research into health hazards, means of limiting exposure and other important health issues in our industry. However, most of the work done is focused on the tire industry and involves only some of the largest of our rubber manufacturing organizations. While this is a very important and significant segment of the rubber industry, it is a limited area both in terms of numbers of workers involved, as well as the variety of materials used.

There are a great many smaller rubber manufacturing operations which for a variety of reasons are never made aware of new findings in the area of chemical exposure, workplace safety, etc., until new compliance regulations are implemented. Even then, they are often overlooked. These factories range from the basic garage shop employing 3-10 people to the moderate size shops employing several hundred. Most of these are involved in mechanical goods operations which involve a wider range of materials and chemicals than the tire companies. They also tend to have less capital to invest in control measures. This group of smaller companies is recognized by most authorities as one of the next major hurdles in improving occupational health. Even now, they are largely overlooked and ignored.

This column will tend to focus on the needs and requirements of these smaller companies. While funds available for investment are more limited, there are a number of reasonably simple, inexpensive measures that can be implemented to improve working conditions and reduce exposure of workers to chemicals. This column has been divided into two parts. Part 1, published this month, will cover control of worker exposure to chemicals through a systems approach. Engineering changes, including material modification, automation/isolation, local exhaust ventilation and work practices, will be discussed.

The basics

When it comes to chemical exposure in the workplace, there are three basic rules. I call them "Jon's Laws":

* First Law - Don't eat it.

* Second Law - Don't breathe it.

* Third Law - Don't get it on you. All attempts to limit chemical exposure in the workplace revolve around these rules. Virtually all rubber manufacturers have the same types of problems in the same types of manufacturing areas. The specific operations involved include:

* Weighing chemicals

* Mixing

* Secondary processing

* Fabrication/preparation

* Curing

* Final inspection/repair Specific exposure problems normally involve dust, solvents and fumes.

How can they be controlled?

Control of worker exposure to the chemicals we use requires a systems approach. No one type of control alone is adequate. And alternative means should be available.

In addition, it requires education. All personnel in the company need to be aware of not just the rules, but the intent of the rules. This is part of the intent of the "Right to Know" legislation. In passing through an area, even an untrained person can notice something that "doesn't look right" (spills, high dust concentrations, etc.) and can report it, possibly saving the company from a major problem.

Exposure control must be the same for all personnel. If dust masks are recommended for use by workers in an area, all management personnel who enter the area must be using them also. Too often, managers who enter an area for minutes don't feel the necessity of putting on cumbersome, uncomfortable gear. However, by not using it, a message is transmitted that it really isn't that important. If it's important enough for the worker to do, it's important enough for you to do. Or, stay out of the area.

Any control plan that violates one of these rules will probably not be very effective.

Almost universally, the preferred method of limiting exposure to these materials is through engineering controls. Personal protective equipment should act as a back-up. While some groups would prefer elimination of hazards as the primary means of personal protection, this is not feasible. And with the increased scrutiny all chemicals are receiving, it's likely that even those we now consider safe will soon be found to be dangerous in some fashion.

Each of the work areas mentioned earlier has its unique problems. Each will be reviewed in next month's Tech Service column. However, before beginning that review, let's discuss types of engineering changes available to the smaller company.

(a) a flourine-containing elastomeric copolymer of vinylidene flouride with at least one other ethylenically unsaturated monomer copolymerizable therewith, wherein the flourine-containing elastomeric copolymer does not contain bromine, iodine or double bond;

(b) an organic peroxide;

(c) a polyfunctional compound;

(d) at least one member selected from the group consisting of bivalent metal oxides; and

(e) an organic base.

TPEs having isobutylene block and

cyclized diene blocks

U.S. patent: 4,910,261 Issued: March 20, 1990 Inventors: Gabor Kaszas, Judith E. Puskas and Joseph P. Kennedy Assigned: Edison Polymer Innovation Corp.

A block copolymer comprising polyisobutylene midblock and polymerized diene end blocks, or a multiblock copolymer comprising a polyisobutylene elastomeric block flanked by blocks of the polymerized diene containing partially cyclized segments wherein the ratio of weight average molecular weight to number average molecular weight of said midblock is more than about 1.5, said polymerized diene being cyclized.

Oil-resistant and anti-degrading

rubber article

U.S. patent: 4,190,267 Issued: March 20, 1990 Investors: Motofumi Oyama, Yoichiro Jubo and Toshiharu Honda Assigned: Nippon Zeon Co. Ltd.

A method of preventing degradation of rubber articles caused by load-carrying additives or detergent-dispersants contained in a mineral oil when the rubber articles are in contact with the mineral oil containing said load-carrying additives or detergent-dispersants for an extended period which method comprises forming at least the surface of said rubber article from a sulfur-vulcanized product of a copolymer rubber having polymer chains consisting of:

1) unsaturated nitrile selected from the group consisting of acrylonitrile and methacrylonitrile;

2) a conjugated diene selected from the group consisting of butadiene, isoprene and 1,3-pentadiene; and

3) at least one member of the group consisting of units derived from unsaturated carboxylic acids, alkyl esters of unsaturated carboxylic acids, alkoxy alkyl acrylates, allyl glycidyl ether, vinyl chloroacetate, ethylene, butene-1 and isobutylene and units resulting from the hydrogenation of units from a conjugated diene.

Material modification Material modification involves substituting a material that is inherently less hazardous than alternatives. In the case of dusts from chemicals, alternative forms of the chemicals are often available. These include oil-treated powders, powders predispersed in a binder, compacted materials, flakes or granules. While use of these may require some alteration of the mixing process, they will often have significantly lower dust exposure problems.

In the case of solvents, there may be alternate solvent systems available that do not carry the same risk as the original system. In many shops involved in bonding of rubber to metal, one of the major solvent exposure problems occurs in the area where the metals are prepared with adhesives. Currently, there are several water based adhesives being worked on and marketed by the major adhesive manufacturers that reduce the exposure problem.

Automation/isolation Once materials have been established, they must be handled. And there will be materials that create dusts, fumes, etc., that must be dealt with. One of the more popular recommendations of industrial hygienists is to install automated weighing systems. These can be very useful and functional in isolating the workers from dust and where there are a large number of the same materials weighed the same way, day in and day out, they may make economic sense. In tire or retread operations, for example, that deal with 10 to 50 different formulations on a regular basis, these systems can work well.

However, the small- to medium-size mechanical goods shop may work with 200 to 700 different formulations in quantities ranging from 25 lb. mill batches to 450 lb. internal mixes. In this environment, automated systems become very expensive and of limited utility.

Even in these shops, one step towards automation that can be taken is the purchase of pre-weighed, packaged ingredients. In some situations these will make sense. While the per pound cost will normally increase, no capital expenditure is required by the user and some of the increased cost may be recovered through reduced material losses and reduced cleaning costs.

Local exhaust ventilation Local exhaust ventilation (LEV) is the most widely used form of engineering control. It is also probably the most practical of the engineering controls for the small- to medium-size shop. It has a wide range of effectiveness, depending on design of the system, maintenance of the system and proximity of other devices, such as man-cooler fans.

For LEV to be effective, there are several key considerations:

* Capture distance must be minimized.

* Sufficient air volume and velocity must be provided.

* The amount of enclosed area must be maximized while the amount of open face area is minimized.

* Cleanouts must be provided for duct maintenance.

* Work with gravity (downdraft or side draft for bag dumping: canopy for hot fumes).

* Pressure drops in entries and ducting must be minimized.

* Hoods and enclosures must have uniform airflow distribution.

* System must be designed to work under negative pressure.

* Regular maintenance.

Work practices While this is not strictly an engineering control, it requires active engineering thought to review work practices with an eye towards reducing worker exposure to chemicals. Many workers actively perform this function for themselves, on the job. A recent study made by the United Rubber Workers in conjunction with OSHA found that there were significant differences in workers' exposure to chemicals on different shifts. The only reason that could be found for the different exposure was differences in work practices.

The following are general work practice rules that can minimize dust exposure:

* Spills should be cleaned up promptly using vacuum or wet sweeping. Dry sweeping and use of compressed air to "blow" materials along the floor should always be avoided. It makes the problem worse.

* Handle all powders using slow, even motions.

* Make sure access doors in ventilation systems are closed.

* No eating, drinking, smoking in work areas.

* Workers should wash when leaving work area for breaks and meals.

* All protective clothing recommended should be worn.

* Dirty, contaminated clothing should be cleaned at regular intervals. Possibly institute use of commercial cleaning service.

* Keep work areas uncluttered.

* Avoid rough handling of empty containers.

* Use scoops to transfer chemicals from bags to weigh containers - not hands.

* Minimize the drop distance when dumping out bags or scoops.

* When several materials are weighed into the same weigh-up container, put the least dusty material (wax, stearic acid, etc.) on top.

* Keep unused containers covered/closed.

* Seal up leaks/tears in bags/drums.

* Allow adequate time for the work to be performed.

Part 2 of this column on chemical exposure in the workplace will appear next month in the July 1990 issue of Rubber World. Solutions for specific work areas, including compounding/weigh-up, mixing, secondary processing, fabrication/preparation, curing and final inspection/repair, will be covered.