Exclusion of Causation Expert Upheld

The Seventh Circuit recently held that a lower court was correct to preclude a proposed causation expert from testifying for the plaintiffs in a suit relating to a plaintiff''s alleged exposure to chlorine gas at an Indiana amusement park.  See  Kent Higgins, et al. v. Koch Development Corp., No. 14-2207 (7th Cir. 7/20/15).

At the park, plaintiff allegedly inhaled an unspecified amount of chemical fumes that lingered in the air near malfunctioning equipment.  Complaining of chest tightness, burning eyes, shortness of breath, and nausea, Higgins visited the emergency room later that day, where he was diagnosed with “mild chemical exposure” and discharged with instructions to follow up with his primary
care physician. More than a year later he was diagnosed with reactive airways dysfunction syndrome (“RADS”) and chronic asthma. 

This treater, Dr. Haacke, was offered as an expert, and when challenged, plaintiff's argument appeared to be that she was qualified merely because she was a board certified pulmonologist. Although a doctor may have “experience diagnosing and treating asthma … that does not make him qualified to ‘assess its genesis.’” Cunningham v. Masterwear, Inc., 2007 WL 1164832, at *10 (S.D. Ind. Apr. 19, 2007). Plaintiff offered no evidence that Dr. Haacke had ever treated another
patient for chlorine gas exposure or had any training in toxicology. Nor could plaintiff establish that Dr. Haacke employed a reliable methodology in forming her causation opinion (even assuming she was qualified to do so). The expert essentially diagnosed Higgins after listening to his own description of his symptoms and the events at the park—some fourteen months after the fact—and after looking at the results (though not the underlying data) of the pulmonary function study conducted by another doctor the year before.

The record was silent on whether Dr. Haacke considered other possible causes of Higgins’s
ailments and, if so, how and why she ruled them out. That is problematic, because plaintiff argued the doctor was employing “differential diagnosis."  A "differential diagnosis” actually refers to a method of diagnosing an ailment, not determining its cause. See Myers, 629 F.3d at 644. Some courts have recognized a form of  "differential etiology,” as a causation‚Äźdetermining methodology. Even then, to be validly conducted, an expert must systematically “rule in” and “rule out” potential causes in arriving at her ultimate conclusion. There was no showing that this was done.

The experts Ļ work is admissible only to the extent it is reasoned, uses the methods of the discipline, and is founded on data.  Lang v. Kohl’s Food Stores, Inc., 217 F.3d 919, 924 (7th Cir. 2000). Accordingly, it was within the district court’s discretion to deem Dr. Haacke unqualified to
proffer this expert testimony.

 

 

 

Medical Monitoring Class Action Rejected at Pleading Stage

A federal court recently rejected a proposed medical monitoring class action brought by alleged Pepsi drinkers.  The case reminds readers of the importance of the causation element of medical monitoring claims, even though plaintiffs don't need to allege traditional personal injury.  See Riva v. Pepsico, Inc., No. C-14-2929 EMC, 2015 WL 993350 (N.D. Cal.,  3/4/15).

Plaintiffs alleged that two of defendant's beverages contained levels of a chemical, 4–MeI, that caused them to experience an “increased risk of cancer,” specifically bronchioloalveolar cancer.  Plaintiffs sought  medical monitoring as a remedy; specifically, seeking an order requiring Pepsi to establish a “fund from which those individual class members can seek monetary recovery for the costs of actual or anticipated medical monitoring expenses incurred by them.”  Plaintiffs alleged that outcomes in bronchioloalveolar cancer show a clinically significant benefit from early evaluation, detection, and diagnosis. 

California is one of the few states that recognizes a claim for medical monitoring. “In the context of a toxic exposure action, a claim for medical monitoring seeks to recover the cost of future periodic medical examinations intended to facilitate early detection and treatment of disease caused by a plaintiff’s exposure to toxic substances.” Potter v. Firestone Tire & Rubber Co., 6 Cal.4th 965, 1004–05, 25 Cal.Rptr.2d 550, 863 P.2d 795 (1993). In Potter, the California Supreme Court identified five factors in determining the reasonableness and necessity of monitoring:
(1) the significance and extent of the plaintiff’s exposure to chemicals;
(2) the toxicity of the chemicals;
(3) the relative increase in the chance of onset of disease in the exposed plaintiff as a result of the exposure, when compared to
(a) the plaintiff’s chances of developing the disease had he or she not been exposed, and
(b) the chances of the members of the public at large of developing the disease;
(4) the seriousness of the disease for which the plaintiff is at risk; and
(5) the clinical value of early detection and diagnosis.

Based on such factors, the trier of fact decides, “on the basis of competent medical testimony, whether and to what extent the particular plaintiff’s exposure to toxic chemicals in a given situation justifies future periodic medical monitoring.” Id.

Defendant attacked the medical monitoring claim under Rule 12(b)(6), particularly as to the Potter factors related to whether medical monitoring is reasonable and necessary.  Accordingly, the Court examined the allegations related to these critical Potter factors: plaintiff’s exposure to chemicals; the toxicity of the chemicals; and the relative increase in the chance of onset of disease in the exposed plaintiff as a result of the exposure, when compared to (a) the plaintiff’s chances of developing the disease had he or she not been exposed, and (b) the chances of the members of the public at large of developing the disease.

To demonstrate the proximate causation element of the claim, a plaintiff seeking medical monitoring must. among other things, show the significance of her exposure to the toxic chemical. Potter, 6 Cal.4th at 1009, 25 Cal.Rptr.2d 550, 863 P.2d 795; see also Abuan v. Gen. Elec. Co., 3 F.3d 329, 335 (9th Cir.1993) (applying comparable Guam law on medical monitoring). The California Supreme Court has explained, “[e]vidence of exposure alone cannot support a finding that medical monitoring is ... necessary.” Lockheed Martin Corp., 29 Cal.4th at 1108–09, 131 Cal.Rptr.2d 1, 63 P.3d 913. A plaintiff must demonstrate sufficient severity of exposure (its significance and extent) and that “the need for future monitoring is a reasonably certain consequence of [the] toxic exposure” Id. at 1109, 131 Cal.Rptr.2d 1, 63 P.3d 913 (citation omitted).

In this case, Plaintiffs alleged that the chemical had been found to cause lung tumors in laboratory animals -- at a daily dose thousands of times higher than the amount in soda.  Plaintiffs sought to represent a class of all persons who purchased Diet Pepsi or Pepsi One within a four-year period, regardless of consumption amount. What was missing was any allegation of what the significance of this unspecified exposure to the chemical may be; they did not allege what threshold level of exposure allegedly created the increased risk.

Thus, there was insufficient information about the significance and extent of exposure of the class to make the necessary ultimate showing that “the need for future monitoring is a reasonably certain consequence of [the] toxic exposure” Lockheed Martin Corp., 29 Cal.4th at 1109, 131 Cal.Rptr.2d 1, 63 P.3d 913. They simply failed to demonstrate a credible risk of bronchioloalveolar cancer resulting from the human consumption of cola products at the levels alleged by the named plaintiffs. In fact, if anything, the specific scientific finding incorporated into the Complalnt from the mice study was that the amounts of 4–MeI ingested in cola products “may not be significant.”

The Court also found that Plaintiffs had not sufficiently pled their injury or shown the toxicity of 4–MeI. It was not enough thatt 4–MeI is on the Proposition 65 list of known carcinogens, that a toxicologist has stated that there is “no safe level of 4–MeI,” and that advocacy groups have called for the FDA to ban 4–MeI.  The full picture was that “caramel coloring” (the manufacturing of which allegedly produces 4–MEI as a byproduct) is “generally recognized as safe” when used in accordance with good manufacturing practice and as a food color additive. Under the FDCA, the inclusion of “caramel color” as a “color additive” means that the FDA has determined that caramel coloring has not been found “to induce cancer when ingested by man or animal.” 21 U.S.C. § 379e(b)(5)(B).

So while Plaintiffs adequately pled that 4–MeI is toxic and is, generally speaking, a carcinogen—i.e., that 4–MeI is capable of causing cancer, they had not adequately pled their specific theory of injury—an increased risk for bronchioloalveolar cancer sufficient to warrant medical monitoring—“above the speculative level.” Twombly, 550 U.S. at 555. Plaintiffs are not mice, and there was nothing in the Complaint, or the studies incorporated by reference, to suggest that 4–MeI causes this specific form of lung cancer in humans. The same mouse study found no increased cancer in rats and discussed a “species difference” identified in previous studies in terms of how various species absorb, distribute, metabolize, and excrete this very chemical. So this study did not lead to a plausible inference that these Plaintiffs are at increased risk of the specific lung cancer for which they request screening. 


In short, the  Plaintiffs failed to plead factual content to show they had been injured due to a “significant” increase in their risk of lung cancer sufficient to justify medical testing in the absence of any symptoms or present injury. See Potter, 6 Cal.4th at 1008–09, 25 Cal.Rptr.2d 550, 863 P.2d 795. The only factual content supporting the allegation of increased risk of lung cancer came from scientific studies, which had no demonstrable bearing on cancer toxicity for humans at the consumption levels alleged in the case at bar.

A plaintiff seeking medical monitoring must show a need for “specific monitoring beyond that which an individual should pursue as a matter of general good sense and foresight.” Potter, 6 Cal.4th at 1009, 25 Cal.Rptr.2d 550, 863 P.2d 795. In this case, Plaintiffs sought CT scans of their lungs and molecular screening for lung cancer. Lung scans are not needed to remedy injury absent a credible showing that 4–MeI causes this lung cancer in humans.

The Court took the Prop 65 argument head on.  Proposition 65 is broad; its listing embraces “ substances listed as human or animal carcinogens. In other words, “the Proposition 65 list includes chemicals that are known to cause cancer in animals, even though it has not been definitively established that the chemicals will cause cancer in humans.” Baxter Healthcare, 120 Cal.App.4th at 352, 15 Cal.Rptr.3d 430. Furthermore, listing under Proposition 65 only requires one excess case of cancer in an exposed population of 100,000, assuming lifetime exposure at the level in question. Because the burden on a defendant to fund medical screening for thousands, potentially millions, of people is so substantial, the Potter factors serve a critical gatekeeping function, regulating a potential flood of costly litigation; Potter requires a higher level of proof of health risk than that required for inclusion of a substance on the Proposition 65 list.

Finally, the Court addressed the increased risk above background, and other possible sources of exposure.  There can be many possible “causes,” indeed, an infinite number of circumstances which can produce an injury or disease. A possible cause only becomes “probable” when, in the absence of other reasonable causal explanations, it becomes more likely than not that the injury was a result of its action. This is the outer limit of inference upon which an issue may be submitted to the jury. As a result, under California personal injury law the mere possibility of causing cancer alone is insufficient to establish a prima facie case.

The Court said that this concept of causation inheres in the Potter test for the reasonableness of medical monitoring; the trier of fact considers, among other factors, “the relative increase in the chance of onset of disease in the exposed plaintiff as a result of the exposure, when compared to (a) the plaintiff’s chances of developing the disease had he or she not been exposed, and (b) the chances of the members of the public at large of developing the disease.” Potter, 6 Cal.4th at 1009, 25 Cal.Rptr.2d 550, 863 P.2d 795. Consistent with this approach, the Ninth Circuit has affirmed a grant of summary judgment where plaintiffs seeking medical monitoring failed to introduce facts regarding the “quantitative (or even qualitative) increased risk to individuals.” Abuan, 3 F.3d at 335.

The Complaint admitted that there are many sources of consumption of 4–MeI, including “baked goods, confectionary, extruded breakfast cereals, instantaneous soups, and dark beers” as well as “soy sauce and coffee.” The many alternative sources of 4–MeI was problematic to the establishment of any causation between the Pepsi products at issue and the Plaintiffs’ alleged consumption of 4–MeI “at or above certain threshold levels” (whatever those threshold levels, if any, may be). The many sources of 4–MeI prevented these Plaintiffs from satisfying the third Potter factor.

Where the pleadings reveal so many commonly consumed foods with similar levels of a chemicaI, it is implausible to conclude that any alleged increased risk of cancer is “more likely than not” caused by drinking/using one product, said the Court.  As a result, the Plaintiffs’ claims were dismissed. See Twombly, 550 U.S. at 557 (“something beyond the mere possibility of loss causation must be alleged”).

 

 

Fifth Circuit Affirms Exclusion of Plaintiff Causation Experts in Chemical Case

The Fifth Circuit recently affirmed the dismissal of most of a plaintiff's personal injury claims against a chemical company, based on the conclusion that certain expert witness testimony was inadmissible. See Johnson v. Arkema Inc., No.11-50193 (5th Cir. June, 2012).

Plaintiff Johnson worked as a machine repairman at a glass bottling plant in Waco, Texas from May 1998 to the end of 2008. On two separate occasions, first in early June 2007 and again in July 2007, Johnson claims he was directed to perform work in close proximity to a device known as a C-4 Hood, which was designed, manufactured, and installed by defendant. C-4 Hoods are
utilized to apply a chemical coating to the glass bottles as the bottles are transported along a conveyor belt. According to Johnson, the C-4 Hood he worked near to on those two occasions failed to perform its proper functions, resulting in his alleged exposure to harmful chemicals.

Plaintiff sued. Arkema then filed motions to exclude the opinions of Dr. Richard Schlesinger, Johnson’s expert toxicologist, and Dr. Charles Grodzin, Johnson’s expert pulmonologist, under Federal Rule of Evidence 702 and the Supreme Court’s decision in Daubert v. Merrell Dow Pharm., Inc., 509 U.S. 579 (1993). Arkema also filed a motion for summary judgment, contending that absent those experts, Johnson was unable to present scientifically reliable evidence establishing that exposure to the chemicals can cause restrictive lung disease and pulmonary
fibrosis (his alleged injury types). The district court granted the motions, and plaintiff appealed. 

On appeal, plaintiff contended that the district court abused its discretion in excluding Dr. Schlesinger’s expert opinion on general causation.  The district court excluded Dr. Schlesinger’s testimony after determining, inter alia, that: (1) Dr. Schlesinger could not cite to one epidemiological or controlled study of humans indicating that exposure to the relevant chemicals could cause restrictive lung disease and pulmonary fibrosis; (2) the scientific literature was devoid of any data or peer reviewed articles indicating that exposure to the two chemicals will result in chronic lung disease, and such a proposition is not generally accepted in the scientific community.

Plaintiff argued that the two fell into a "class" of chemicals that have been shown to cause these injuries. In forming a reliable opinion regarding the effects of exposure to a particular chemical, an expert may extrapolate data from studies of similar chemicals. BUT to support a conclusion based on such reasoning, the extrapolation or leap from one chemical to another must be reasonable and scientifically valid.  Thus, courts are free to reject a theory based on extrapolation when there is simply too great an analytical gap between the data and the opinion proffered. Here, save for highlighting their shared classifications as "irritants," the expert did not attempt to explain any direct correlation or “fit” between the chemicals at issue and the known scientific data concerning exposure to, for example, chlorine, ammonia, or nitric acid vapor. Accordingly, given the diverse chemical structures and toxicities of irritants, which plaintiff acknowledged, the district court did not abuse its discretion in concluding that Dr. Schlesinger’s “class of chemicals” theory presented “too great an analytical gap between the data and the opinion proffered.

The next issue was reliance on language in an MSDS, which is useful for many of our readers in toxic tort cases.  The district court found the "warning" language in a competitor's MSDS to be irrelevant and unreliable because: it did not clearly state a causation conclusion, and, most importantly, Johnson did not provide any science behind the MSDS, such as the duration or concentration of exposure needed to produce the noted effects, or the scientific literature relied upon by the drafter for the statements contained in the MSDS.  Under such circumstances, the MSDS, standing alone, need not have been accorded any weight. Plaintiff also relied on general hazard language in defendant's own MSDS. But could cite no authority for the proposition that material safety data sheets constitute per se reliable support for an expert’s opinion. To the contrary, in exercising its discretion as a gatekeeper, a court may refrain from treating a MSDS as reliable until it is presented with scientific evidence justifying the relevant statements found within the MSDS.

Finally, Johnson contended that he was exposed to amounts of one of the chemicals (HCl) that were between two and ten times the permissible exposure levels set by OSHA, NIOSH, and the Acute Exposure Guideline Levels set by the National Research Council. Regulatory and advisory bodies such as IARC, OSHA and EPA utilize a “weight of the evidence” method to assess the carcinogenicity or toxicity of various substances in human beings and suggest or make prophylactic rules governing human exposure. This methodology results from the preventive perspective that the agencies adopt in order to reduce potential public exposure to possibly harmful substances. The agencies’ threshold of proof is lower (for policy reasons) than that appropriate in tort law, which traditionally makes more particularized inquiries into cause and effect, and requires a plaintiff to prove that it is more likely than not that another individual has caused him or her harm. See generally Wright v. Willamette Industries, Inc., 91 F.3d 1105, 1107 (8th Cir.1996). Thus, such regulatory chemical guidelines are not necessarily reliable in all toxic tort cases. And a court should confirm the underlying basis for their  proscriptions before an expert’s reliance on them can pass Daubert muster. Here, plaintiff did not provide any scientific data or literature to explain how or why the various exposure limits and guidelines were established for the chemicals. Similarly, he had no evidence that the guidelines and exposure limits existed to protect people from developing severe restrictive lung disease and pulmonary fibrosis, his diseases. Thus, the court concluded that the OSHA, NIOSH, and NRC guidelines and exposure limits, standing alone, were insufficient to demonstrate abuse of discretion on the part of the district court.

As to the other expert, Dr. Grodzin’s research and analysis essentially mirrored Dr. Schlesinger’s save for one key distinction: Dr. Grodzin performed a so-called “differential diagnosis” of Johnson. A reliable differential diagnosis typically, though not invariably, is performed after physical examinations, the taking of medical histories, and the review of clinical tests, including laboratory tests, and generally is accomplished by determining the possible causes for the patient’s symptoms and then eliminating each of these potential causes until reaching one that cannot be ruled out.  Even in jurisdictions that accept this questionable approach to causation, the results of a differential diagnosis are far from reliable per se. For example, before courts can admit an expert’s differential diagnosis, which, by its nature, only addresses the issue of specific causation, the expert must first demonstrate that the chemical at issue is actually capable of harming individuals in the general population, thereby satisfying the general causation standard. In other words, the suspect has to be reasonably and reliably "ruled in."

Here, Dr. Grodzin’s differential diagnosis was based on the presumption that the two chemicals  were actually capable of causing restrictive lung disease and pulmonary fibrosis in the general population. Dr. Grodzin did not present any reliable or relevant scientific evidence to bolster this assumption. Consequently, the fact that Dr. Grodzin claimed he conducted a differential
diagnosis did not save his opinion from the same fate as Dr. Schlesinger’s opinion.

 (Note, the court concluded that plaintiff did not need expert witnesses to demonstrate that his immediate acute injuries after exposure and which allegedly sent him to the emergency room, could have been caused by the chemical.  Thus, this part of the case was remanded.)

 

 

 

Jury Rejects Medical Monitoring Claim in Coal Dust Litigation

A West Virginia jury last week ruled in favor of defendant Massey Energy Co. in a class action accusing the company of exposing plaintiffs from an elementary school to toxic coal dust. Dillon et al. v. Goals Coal Co. et al., No. 05-c-781 (Circuit Ct. Raleigh County, W.Va.).

The plaintiffs first filed suit in 2005, complaining about a coal silo near the Marsh Fork Elementary School in Raleigh County.  Coal dust allegedly drifted from the silo into the school, exposing the plaintiffs, and putting them at increased risk of lung disease.  The court eventually certified a class of about 300.

Plaintiffs sought a medical monitoring program to early detect the alleged effects of the exposure.  In order to sustain a claim for medical monitoring expenses under West Virginia law, the plaintiff must prove that (1) he or she has, relative to the general population, been significantly exposed; (2) to a proven hazardous substance; (3) through the tortious conduct of the defendant; (4) as a proximate result of the exposure, plaintiff has suffered an increased risk of contracting a serious latent disease; (5) the increased risk of disease makes it reasonably necessary for the plaintiff to undergo periodic diagnostic medical examinations different from what would be prescribed in the absence of the exposure; and (6) monitoring procedures exist that make the early detection of a disease possible.  See Bower v. Westinghouse Electric Corp., 522 S.E.2d 424 (W. Va. 1999).

The defense challenged both the significant exposure and increased risk prongs. The jury rejected the medical monitoring claim after a 2 week trial.

FDA Considering Rules on Acrylamide in Food

The FDA is considering issuing guidelines on acrylamide content in food.  The agency has published a notice seeking comments from industry on the issue.

Acrylamide is a chemical formed primarily in baked and fried foods by a reaction between sugars and the amino acid asparagine. The reaction is partly responsible for the golden color and tasty flavor of baked, fried, and toasted foods. In 2002, some Swedish scientists reported unexpectedly high levels of acrylamide in carbohydrate-rich foods and also published a study associating the chemical to cancer in laboratory rats. Further research subsequently determined that acrylamide can form in some foods during certain types of high-temperature cooking.

FDA has not yet issued guidance for manufacturers on reducing acrylamide in food. However, it is anticipated by the agency that new information will soon be available about the toxicology of acrylamide, which may shed light on acrylamide's potential carcinogenicity in laboratory animals. Readers of MassTortDefense know how difficult it is to leap from animal studies to causation conclusions in human beings, because of the physiological and metabolism differences between species, the excessive dosages that are (and typically must be) given to experimental animals, and the varying biological defense mechanisms that species have to environmental insults.

International efforts to develop approaches to acrylamide mitigation are also beginning to prove successful. Moreover, FDA is aware that at least some manufacturers in the United States are seeking ways to reduce acrylamide in their products. In this context, FDA is considering issuing guidance for industry on reduction of acrylamide levels in food products.

Health Canada recently added acrylamide to that nation’s toxic substances list, as part of its ongoing review of over 200 chemical substances in commercial use. It stated that current consumption levels “may constitute a danger in Canada to human life or health,” but it also acknowledged that research into a possible carcinogenic link for humans has so far been inconclusive.

In fact, dietary intakes of acrylamide are not related to increased risks of brain cancer, according to a recently released study of 58,279 men and 62,573 women, published by Maastricht University in the Netherlands. J.G.F. Hogervorst, et al., “Dietary Acrylamide Intake and Brain Cancer Risk,” 18 Cancer Epidemiology, Biomarkers & Prevention (2009).  Researchers have also reported in the Journal of the National Cancer Institute that dietary acrylamide was not linked to lung cancer risk, and that the compounds may even reduce the risk in women. "Lung Cancer Risk in Relation to Dietary Acrylamide Intake," 101(9) JNCI 651-662 (2009).

 

 

In seeking comments, the FDA has asked food manufacturers to respond with details of any manufacturing changes they have made, the success and cost-effectiveness of those changes, methods for acrylamide reduction that could be appropriate for smaller manufacturers, and changes to on-pack instructions for consumers to mitigate acrylamide formation.

 

 

Nano-particle Study Generates More Heat Than Light

A new study published in the European Respiratory Journal is generating media attention, and some observers assert it may have far-reaching implications for the nano-tech industry. Is this warranted?

In this study, Song, et al., Exposure to nano-particles is related to pleural effusion, pulmonary fibrosis and granuloma, 34(3) Eur. Respir. J. 559-567 (2009), researchers at China's Capital University of Medical Sciences linked lung disease in seven Chinese workers, two of whom reportedly died, to nano-particle exposures in a print plant where a paste containing nano-particles was sprayed onto a polystyrene substrate, with subsequent heat-curing.

The study reported that seven young female workers (ages 18–47), exposed to nano-particles for 5–13 months, were admitted to the hospital, all with shortness of breath and pleural effusions. Polyacrylate, consisting of nano-particles, was confirmed in the workplace. Pathological examinations of the patients' lung tissue displayed non-specific pulmonary inflammation, pulmonary fibrosis, and foreign-body granulomas of pleura. By transmission electron microscopy, nano-particles were observed to have lodged in the cytoplasm and caryoplasm of pulmonary epithelial and mesothelial cells, but also were located in the chest fluid.

The authors expressed concern that long-term exposure to some nano-particles may be related to serious damage to human lungs.  But, putting the media reception aside, this study appears to do more to highlight the common sense need to follow good industrial hygiene practices than to provide compelling evidence of any unique health risks posed by engineered nano-particles. The plant sprayed a strong chemical paste and then heated plastic material in an enclosed space apparently lacking ventilation.  The room in which the women worked was small and unventilated for a significant part of their exposure period. Only on occasion, they wore mere "cotton gauze masks." 

From the study it appears that the workers had a complicated exposure history to a mix of chemicals; while there was a reported association of nano-particles with lung disease, it is unclear which, if any, of the chemical exposures might have contributed to the lung issues. Readers of MassTortDefense know that an association is not causation.  For example, formation of thermodegradation fume products are known to cause significant occupational disease, and paint spraying has been shown to be potentially harmful long before nano-sizing of chemicals was utilized. 

Moreover, sufficient exposure information necessary to even begin to think about a causal connection between exposure to nano-sized particles in the paste/dust and lung and heart disease in the workers was missing.  Clearly, there may be alternative explanations for what the study authors described finding in the patients.

As noted here before, NIOSH emphasizes the use of a variety of engineering control techniques, implementation of a risk management program in workplaces where exposure to nanomaterials exists, and use of good work practices to help to minimize worker exposures to nanomaterials.