Subpart Z
Yes. This section applies to all occupational exposures to MDA (4,4′-diaminodiphenylmethane), CAS No. 101-77-9, except as limited by the exceptions in paragraphs (a)(2) through (a)(7) of the standard. See 1910.1050(a)(1).
The standard does not apply when initial monitoring shows the product cannot release MDA in excess of the action level under the expected worst-case conditions of processing, use, and handling, and where no dermal exposure to MDA can occur. Employers relying on this exemption must still meet any recordkeeping requirements described elsewhere in the rule. See 1910.1050(a)(2) and the recordkeeping requirement in 1910.1050(a)(8).
An employer may rely on objective data when that data reasonably demonstrate the product is not capable of releasing MDA under the expected worst-case conditions of processing, use, and handling, and when no dermal exposure to MDA can occur. The employer must document and retain the objective data and the basis for relying on it as required by the rule. See 1910.1050(a)(3) and the record requirement in 1910.1050(a)(8).
No, the standard does not apply to storage, transportation, distribution, or sale of MDA when the MDA is in intact containers sealed to contain dusts, vapors, or liquids, except that employers must still comply with the Hazard Communication requirements and paragraph (d) of the MDA standard. See 1910.1050(a)(4) and 29 CFR 1910.1200.
No. The construction industry is excluded from this MDA standard; exposures to MDA in construction are covered by 29 CFR 1926.60, and the MDA general industry rule excludes construction per 1910.1050(a)(5).
Yes, materials in any form that contain less than 0.1% MDA by weight or volume are exempt from the standard, except where paragraph (a)(8) requires the employer to keep supporting records for the exemption. See 1910.1050(a)(6) and 1910.1050(a)(8).
Finished articles containing MDA are exempt from the standard provided they meet the rule's finished-article criteria and are otherwise exempted by paragraphs (a)(2)–(a)(7); however, exemption documentation may still be required under paragraph (a)(8). A "finished article" is an item formed to a specific shape or design whose end-use function depends on that shape or design and, where applicable, is fully cured by the conditions necessary to complete the desired chemical reaction. See 1910.1050(a)(7) and the finished article definition in 1910.1050(c).
The employer must retain records of the initial monitoring results or the objective data that support the claimed exemption and must document the basis for relying on that data, in accordance with the recordkeeping provisions of paragraph (n) of the standard. See 1910.1050(a)(8) and 1910.1050(n).
The action level for airborne MDA is 5 parts per billion (ppb) as an eight-hour time-weighted average. See the definition of action level in 1910.1050(b).
Dermal exposure to MDA occurs when employees handle, apply, or use mixtures or materials containing MDA in non-airborne forms that meet either of two conditions: (1) liquid, powdered, granular, or flaked mixtures containing MDA concentrations greater than 0.1% by weight or volume; or (2) materials other than finished articles containing MDA in concentrations greater than 0.1% by weight or volume. See the dermal exposure definition in 1910.1050(b).
Employers must ensure no employee is exposed to airborne MDA above 10 ppb as an 8‑hour TWA, and no employee is exposed above a short-term exposure limit (STEL) of 100 ppb. See 1910.1050(c) and the PEL statement in 1910.1050(d).
The employer must develop a written emergency plan for each workplace with the possibility of an MDA emergency, equip employees correcting emergency conditions with required personal protective equipment until the emergency is abated, and include provisions for alerting and evacuating affected employees consistent with 29 CFR 1910.38 and 1910.39. See 1910.1050(d)(1)(i)–(iii).
Where there is the possibility of employee exposure to MDA due to an emergency, the employer must develop means to promptly alert employees who could be directly exposed and immediately evacuate affected employees who are not engaged in correcting the emergency. See 1910.1050(d)(2).
Employee exposure must be determined from breathing zone air samples that represent each employee’s exposure over an eight‑hour period for the TWA and from 15‑minute breathing zone samples to determine the STEL. Representative sampling must cover each shift and job classification where exposures may occur. See 1910.1050(e)(1)(i)–(iii).
The employer must perform initial monitoring for any workplace covered by the standard to accurately determine airborne MDA concentrations. If initial monitoring shows exposures at or above the action level but at or below the PEL, repeat monitoring at least every six months; if above the PEL, repeat monitoring at least every three months. The employer may reduce the frequency from three to six months for an employee if two consecutive measurements at least seven days apart show the exposure decreased below the TWA but remained above the action level. See 1910.1050(e)(2) and 1910.1050(e)(3)(i)–(iii).
The employer may discontinue monitoring for an employee if initial monitoring shows exposures below the action level, except where paragraph (e)(5) requires monitoring; likewise, periodic monitoring may be discontinued if at least two consecutive measurements taken at least seven days apart show exposures below the action level. Additional monitoring must be instituted whenever changes in production processes, chemicals, control equipment, personnel, or work practices may result in new or increased MDA exposures, or whenever the employer has reason to suspect such a change. See 1910.1050(e)(4)(i)–(ii) and 1910.1050(e)(5).
Monitoring must be accurate to a 95% confidence level within ±25% for airborne concentrations of MDA. Employers must notify each affected employee of monitoring results in writing within 15 working days after receiving the results, either individually or by posting results in an accessible location. If PELs are exceeded, the written notification must include corrective actions being taken to reduce exposures. See 1910.1050(e)(6) and 1910.1050(e)(7)(i)–(ii).
The employer must routinely inspect employees' hands, face, and forearms that are potentially exposed to MDA; any other potential dermal exposures reported by employees must be referred to medical personnel. If the employer determines an employee has been exposed dermally, the employer must determine the source, implement protective measures to correct the hazard, and maintain records of corrective actions under paragraph (n). See 1910.1050(e)(8)(i)–(iii).
The employer must establish regulated areas where airborne concentrations of MDA exceed or can reasonably be expected to exceed the permissible exposure limits; additionally, where employees are subject to dermal exposure to MDA the employer must designate those work areas as regulated areas. See 1910.1050(f)(1)(i)–(ii).
The STEL for MDA is 100 ppb and is measured from a breathing zone air sample collected over a 15‑minute sampling period. See the PEL/STEL statements and sampling guidance in 1910.1050(c) and 1910.1050(e)(1)(i).
The action level (5 ppb TWA) triggers monitoring and certain program requirements, while the PEL (10 ppb TWA and 100 ppb STEL) represent the exposure ceilings employers must not exceed; monitoring frequency and control measures are determined based on whether exposures are below the action level, between the action level and the PEL, or above the PEL. See the action level definition in 1910.1050(b), and the PELs in 1910.1050(c).
Even when MDA is stored, transported, distributed, or sold in intact sealed containers and therefore exempt from most provisions of the MDA standard, employers still must comply with the Hazard Communication requirements because 1910.1050(a)(4) explicitly preserves obligations under 29 CFR 1910.1200.
Employers must maintain records of the corrective actions taken when exposures occur (per e(8)(iii)) and must keep the initial monitoring results or objective data and the basis for relying on them when claiming exemptions under (a)(2)–(a)(7); these records are retained consistent with the recordkeeping provisions in 1910.1050(n) and the exemption documentation requirement in 1910.1050(a)(8).
Employers must clearly separate regulated areas from the rest of the workplace in a way that minimizes how many people could be exposed to MDA. This means establishing physical boundaries and controls, posting required signs at entrances, and limiting access so only authorized personnel enter 1910.1050(f). Employers should also follow the posting legend requirements in 1910.1050(k)(2)(i) to mark regulated areas.
Only authorized persons may enter regulated areas. The standard requires that access to regulated areas be limited to authorized personnel to prevent unnecessary exposures 1910.1050(f)(3). Employers should document who is authorized and train those employees on the required protective clothing and procedures before entry.
Employers must supply and require the use of the appropriate protective clothing and equipment for everyone entering a regulated area, in accordance with paragraphs (h) and (i) of the MDA standard. That includes respirators where required and protective work clothing like gloves, aprons, face shields, or chemical goggles as described in 1910.1050(h) and 1910.1050(i). Employers must provide these at no cost and enforce their use 1910.1050(f)(4).
Employees are prohibited from eating, drinking, smoking, chewing tobacco or gum, or applying cosmetics in regulated areas. The standard explicitly forbids these activities to prevent ingestion or dermal exposure to MDA 1910.1050(g). Employers must enforce the ban and provide suitable lunch and hygiene facilities per the standard.
Employers must institute engineering controls and work practices to reduce and maintain employee exposure to MDA at or below the PELs unless they can demonstrate such controls are not feasible. If feasible controls cannot lower exposures to the PEL, employers must use them to reduce exposure as far as possible and supplement with respirators as allowed 1910.1050(g)(1). The employer’s written compliance program must document these actions 1910.1050(g)(2).
If feasible engineering controls and work practices cannot reduce exposures to the PEL, the employer must use those controls to get exposure as low as possible and supplement them with respiratory protection that meets paragraph (h) of the standard. In other words, respirators are allowed only as a supplement when controls alone are insufficient 1910.1050(g)(1)(ii) and respirator program requirements follow 1910.1050(h).
The written compliance program must describe how the employer will reduce employee exposure to or below the PELs using engineering and work-practice controls and where appropriate, respiratory protection. It also must include a schedule for periodic maintenance (such as leak detection) and a written emergency plan as required in 1910.1050(d) 1910.1050(g)(2). Employers must furnish this program upon request to the Assistant Secretary, the Director, affected employees, and designated employee representatives and review it at least annually 1910.1050(g)(2)(ii).
No — employee rotation is not permitted as a method to reduce exposure to MDA. The standard explicitly prohibits rotation as an exposure control measure 1910.1050(g)(3). Employers must rely on engineering controls, work practices, and permitted respiratory protection instead.
Respirators must be used during periods necessary to install or implement feasible controls, for operations where controls are not feasible, for operations where controls are not yet sufficient to reach the PEL, and during emergencies. The standard lists these four circumstances as respiratory use requirements 1910.1050(h)(1). Employers must also implement a respirator program per 1910.134 as required by 1910.1050(h)(2).
Employers must select and provide the respirators specified in 29 CFR 1910.134 and provide HEPA filters for powered and non-powered air-purifying respirators. For escape, employers must provide either a full-facepiece positive-pressure self-contained breathing apparatus or a full-facepiece air-purifying respirator; and when MDA is liquid or used with heat, provide a combination HEPA filter and organic vapor canister or cartridge for air-purifying respirators 1910.1050(h)(3)(i)(A)-(D). Employers must also implement the respirator program elements in 1910.134(b)-(d),(f)-(m) as required by 1910.1050(h).
If an employee cannot use a negative-pressure respirator, the employer must offer the option of a positive-pressure respirator or a supplied-air respirator operated in continuous-flow or pressure-demand mode 1910.1050(h)(3)(ii). Employers must ensure these alternatives meet the selection and program requirements in 1910.134.
Employers must provide, at no cost, appropriate protective clothing and equipment that prevent contact with MDA, including aprons, coveralls, gloves, head and foot coverings, face shields, and chemical goggles, and any other equipment that meets [1910.133] requirements for eye and face protection 1910.1050(i)(1)(i)-(iv). Employers must ensure employees use this equipment whenever dermal exposure or airborne concentrations above the PEL are present.
Employers must ensure employees remove non-routinely removed contaminated clothing at the end of shift in change rooms, remove other contaminated clothing before leaving a regulated area during the shift, and prevent taking contaminated clothing out of the change room except for authorized laundering, maintenance, or disposal 1910.1050(i)(2)(i)-(iii). Contaminated items to be removed must be placed in closed containers to prevent dispersion and labeled with hazard warnings if taken out of the workplace 1910.1050(i)(2)(iv)-(v).
Employers must provide clean protective clothing, ensure contaminated clothing is cleaned, laundered, repaired, or replaced as needed to maintain effectiveness, and forbid cleaning methods (like blowing or shaking) that reintroduce MDA into the workplace. Employers must ensure laundering prevents release of MDA and inform any external launderers of the hazards and handling requirements 1910.1050(i)(3)(i)-(v). Contaminated clothing must be transported in labeled, sealed, impermeable bags or containers 1910.1050(i)(3)(vi).
Employers must provide clean change rooms with separate storage for protective clothing and street clothes for employees required to wear protective clothing 1910.1050(j)(1)(i)-(ii). Employers must also provide showers at the end of shift for employees who may have airborne exposures at or above the action level, and ensure those employees do not leave the workplace wearing protective clothing 1910.1050(j)(2)(i)-(ii). Where dermal exposure occurs, employers must ensure skin contamination is removed promptly by methods that do not increase dermal absorption 1910.1050(j)(2)(ii).
If employees are exposed to MDA at or above the PEL or are subject to dermal exposure, the employer must provide readily accessible lunch areas; such lunch areas inside the workplace must have positive-pressure, temperature‑controlled, filtered air supply and cannot be in areas with potential dermal exposure 1910.1050(j)(3)(i)(A)-(C). Employees exposed above the PEL or with dermal exposure must wash hands and faces with soap and water before eating, drinking, smoking, or applying cosmetics, and must not enter lunch areas wearing contaminated protective clothing 1910.1050(j)(3)(ii)-(iii).
Employers must include MDA in their Hazard Communication Program under 1910.1200 and ensure employees have access to container labels and safety data sheets. They must post legible signs marking regulated areas with the exact legend required by 1910.1050(k)(2)(i)(A) (or the pre‑2016 legend allowed by 1910.1050(k)(2)(i)(B)). Employers must also make appropriate use of Appendices A and B when preparing safety data sheets 1910.1050(k)(3).
Employers must train employees on MDA at initial assignment and at least annually thereafter in accordance with 1910.1200(h). In addition to Hazard Communication requirements, employers must explain the contents of the MDA standard (including Appendices A, B, and C), describe the medical surveillance and medical removal provisions, and indicate where a copy of the standard is available 1910.1050(k)(4)(i)-(ii).
Contaminated work clothing and equipment must be placed in closed containers that prevent dispersion of MDA outside the container, and any containers taken out of the workplace for cleaning, maintenance, or disposal must bear labels warning of the hazards of MDA 1910.1050(i)(2)(iv)-(v). Employers must also ensure transport uses sealed, impermeable bags or containers and inform any launderer of the hazards 1910.1050(i)(3)(vi) and (i)(3)(iv)-(v).
No — employers must prohibit removal of MDA from protective clothing by blowing, shaking, or any method that would allow MDA to re-enter the workplace. The standard requires cleaning methods that prevent re-dispersal and employer communication to external laundries about preventing release of MDA 1910.1050(i)(3)(ii)-(iv).
Employers must post and maintain legible signs at regulated-area entrances showing the legend exactly: "DANGER MDA MAY CAUSE CANCER CAUSES DAMAGE TO THE LIVER RESPIRATORY PROTECTION AND PROTECTIVE CLOTHING MAY BE REQUIRED IN THIS AREA AUTHORIZED PERSONNEL ONLY" as required by 1910.1050(k)(2)(i)(A). Prior to June 1, 2016 the alternative legend in 1910.1050(k)(2)(i)(B) was permitted.
Employers must make readily available, at no cost, all written materials related to the employee training program, including a copy of the standard. 1910.1050(k)(5)(i) requires that these materials be accessible to all affected employees without charge.
Surfaces contaminated with MDA may not be cleaned with compressed air, but limited dry-cleanup methods are allowed only when HEPA-filtered vacuuming and/or wet cleaning are not feasible. 1910.1050(l)(4) explicitly prohibits compressed air cleaning. 1910.1050(l)(5) permits shoveling, dry sweeping, and other dry clean-up methods only where HEPA-filtered vacuuming and/or wet cleaning are not feasible or practical.
The employer must institute a program to detect MDA leaks, spills, and discharges that includes regular visual inspections of operations involving liquid or solid MDA, and the employer must promptly repair leaks and clean up spills. 1910.1050(l)(2) requires a detection program including regular visual inspections, and 1910.1050(l)(3) requires that all leaks be repaired and liquid or dust spills be cleaned up promptly.
Waste, scrap, debris, bags, containers, equipment, and clothing contaminated with MDA must be collected and disposed of in a way that prevents MDA from re-entering the workplace. 1910.1050(l)(6) requires disposal methods that stop re-entry.
Employers must make medical surveillance available to employees in specified exposure categories and must provide the examinations under the supervision of a licensed physician at no cost to the employee. 1910.1050(m)(1)(i) lists who is covered (employees exposed at or above the action level for 30+ days/year; employees with dermal exposure 15+ days/year; employees exposed in an emergency; employees the employer has reason to believe are dermally exposed based on compliance with 1910.1050(e)(8); and employees who show signs or symptoms of exposure). 1910.1050(m)(1)(ii) requires that all medical examinations and procedures be performed by or under the supervision of a licensed physician at a reasonable time and place and provided without cost to the employee.
An initial medical examination must include a detailed history, a physical exam (including skin and liver signs), and laboratory tests (liver function tests and urinalysis), and it must be provided within 150 days of the standard's effective date or before initial assignment for covered employees unless a compliant exam was done within the previous six months. 1910.1050(m)(2)(i) specifies the required elements: a detailed history covering past MDA and toxic exposures, drug/alcohol/tobacco history, and dermatitis or hepatic disease history; a physical exam including skin exam and signs of liver disease; lab tests including liver function tests and urinalysis; and any additional tests the physician deems necessary. 1910.1050(m)(2)(ii) states no initial exam is required if adequate records show the employee was examined in accordance with the section within the prior six months.