When does a box itself tell us as much as what is inside it? Writer and photographer Bill Sharpsteen set out to answer that question, devoting years to exploring the combined ports of Los Angeles and Long Beach. The result is The Docks, a virtually encyclopedic look at the booming but paradoxically hermetic life of the nation's largest seaport. Why should we care about what happens there? Because, as Sharpsteen explains, what goes on inside the fenced, patrolled perimeter provides fascinating insights into the global forces transforming our society, economy, and environment.

The ports occupy a vast, 10,700-acre industrial landscape of piers, ships, cranes, railroads, warehouses, water highways, and seas of asphalt covered by rows of newly imported cars and stacks of "cans," metal shipping containers in which the seaborne cargo of the world is transported.

Like the Los Angeles metropolis that sprawls across this semiarid region, the ports, by conventional logic, shouldn't exist. Unlike its competitors, San Diego and San Francisco, Los Angeles has no natural harbor. A century ago, the area was a shallow bay with a small fishing community. But through what Mike Davis, author of City of Quartz, has called the "Bismarckian municipal will" of the region's political leaders, breakwaters, massive fill islands, and railroad links transformed the sleepy harbor into a leviathan that now handles 40 percent of U.S. seaborne cargo and 70 percent of U.S. imports from Asia.

Once unloaded, the cans move on trains and trucks to huge distribution centers elsewhere in the Los Angeles Basin. Half of the cargo is swallowed there by a consumer market of around 20 million people; the rest streams out to additional distribution centers in Kansas City, Dallas, and Chicago, and from there to points east and north. Across the country, 3.3 million jobs depend in part on the Los Angeles/Long Beach ports. Sharpsteen employs a biological metaphor: the ports are like a heart pumping goods into the body of the continent through major rail and highway arteries, ending in the vessels and capillaries of city and suburban streets. They look from the air like "an industrial vascular system whose disruption would cause an economic heart attack for the country."

Yet people in the communities that border the ports -- the Los Angeles neighborhoods of San Pedro and Wilmington and Long Beach's West Side -- worry not about metaphorical disease in the national economy but about real ones in their bodies and those of their children. Many call this the Diesel Death Zone, enveloped as it is in a cloud of fumes and soot spewed out by the ships, which burn cheap "bunker fuel" containing up to 3,000 times as much sulfur as conventional diesel, and by the fleets of trucks, locomotives, and cargo-handling vehicles that swarm around them. Added to this are emissions from the hundreds of acres of refineries, tank farms, and pipelines in and around the ports, making the area the largest source of pollution in Southern California.

The most insidious threat comes from particulates, especially those called ultrafines -- invisible and so tiny that they can pass through cell membranes, lodging in tissues and potentially leading to cancer. Children, whose lungs are still developing until the age of 17, are nearly five times more likely to have impaired lung function in areas with high particulate counts, such as those adjacent to freeways -- and ports. While Sharpsteen chronicles all this, he also reports on the progress being made in replacing dirty trucks with cleaner models and in cutting emissions from ships -- the result of a successful lawsuit filed in 2001 by NRDC and the Coalition for Clean Air.

Like ultrafines, much of what is revealed in The Docks is difficult to see from outside. Sharpsteen was initially denied access to the ports, but his persistence paid off with intimate portraits of many of the people who make them tick: longshoremen, independent truckers, ship pilots, tugboat captains, coastguardsmen, shippers, port executives, union officials, and community activists who have fought port expansion and pollution for decades.

The sum is a fine-grained view of how the world's trade is kept flowing, with goods once made in America now imported from abroad (chiefly Asia), courtesy of lower labor costs and looser environmental regulation. What Sharpsteen also reveals is the true cost of those cheap goods -- paid by the environment; by the health of people in the manufacturing countries and in communities here that share space with the goods movement industry; and by the wider dislocations that have come from offshoring so much of our own economy. As much as the shoes, TVs, and computers inside the boxes, it is the chain of engines and hands that moves them that tells the real, important story of the docks.